WO2025202197A1

WO2025202197A1 - A roof truss

Info

Publication number: WO2025202197A1
Application number: PCT/EP2025/058131
Authority: WO
Inventors: Edward Ross SHENTON
Original assignee: Sano Development Ltd
Current assignee: Sano Development Ltd
Priority date: 2024-03-28
Filing date: 2025-03-25
Publication date: 2025-10-02
Anticipated expiration: 2026-09-28

Abstract

A roof truss is disclosed which has a use in constructing a building. One exemplary roof truss (1,11) comprises a bottom chord (2,12), at least one top chord (3,13), and an insulation support frame (4,14). The bottom chord (2,12) is configured to bear upon and be supported by two spaced apart support structures. The top chord (3,13) is connected to the bottom chord (2,12) and configured to support roofing material on a first side of the bottom chord (2,12). The insulation support frame (4,14) extends from the bottom chord (2,12) on a second side of the bottom chord (2,12) opposite the first side. The insulation support frame (4,14) is configured to support building insulation on the second side of the bottom chord (2,12).

Description

A ROOF TRUSS

TECHNICAL FIELD

[0001] The present invention relates to a roof truss. In particular, the present invention relates to a roof truss for use in constructing a building such as a residential building and configured to support a roofing material. According to the present invention the roof truss is modified relative to conventional roof trusses to support insulation material below the level at which the roof truss is supported by support structures within the building.

BACKGROUND

[0002] In building construction, buildings, and particularly residential buildings such as houses, commonly have a pitched roof formed from a plurality of roof trusses arranged in parallel and spaced apart over an uppermost storey of the building. A roof truss is a premanufactured structure, typically formed from timber and configured to be supported by exterior walls of the building, spanning the internal volume of the building. A roof truss defines the shape of the pitched roof and supports roofing material, transferring the weight of the roof downwards onto the building walls.

[0003] A pitched roof can comprise two roof portions which slope downwardly in opposite directions from an apex (or ridge) of the roof towards respective edge regions, known as eaves. Another example comprises a single roof portion which extends from a high side at one edge of the building to a low side at an opposite edge.

[0004] In the former example, the roof trusses each comprise a pair of top chords (sometimes referred to as rafters) which extend downwardly in opposite directions from an apex of the roof, and a bottom chord (sometimes referred to as a tie beam) which extends laterally between and connects the top chords. In the latter example, the roof trusses are generally of a right-angled triangle shape, comprising a top chord which slopes downwardly from the high to the low side, and bracing beneath the top chord. In both cases, the trusses are supported by a wall structure of the building towards either end of the bottom chord, suitably by an elongate component known as a wall plate overlying the tops of the walls. The wall plate is positioned on a top surface of the wall structure, extending along its length, and is usually of a timber material. A timber wall plate is typically around 1.5” (~3.8cm) deep and secured to the top of the wall through straps that secure to the wall. The bottom chord is secured to the wall plate, for instance by nails. The walls may be formed from any known building material so long as they provide sufficient strength to support the weight of the roof structure transferred to the wall plate.

[0005] The roof space defined by the shape of the roof trusses is normally insulated, to resist thermal energy transfer through a ceiling structure of the building, which defines a lower boundary of the roof space. The insulation is conventionally positioned above an inner skin of the ceiling (that is affixed to an underside of the bottom chords of each roof truss), and extends laterally into the roof eaves. The insulation should ideally pass over the wall plate to a position adjacent an inner surface of the roof, between the top chords of adjacent trusses. This serves to insulate a void located between the bottom and top chords adjacent the eaves, in the region of the wall. Insertion of insulation into the void can however be difficult, as the opening into it from the main roof space is usually quite small. This can have the result that the void is inadequately insulated, because the insulation does not extend all the way into it over the wall plate. This can lead to cold zones (or 'cold spots’) forming along an upper part of the wall inside the building on the uppermost storey. Consequences of this can include heat loss, and damp patches appearing on the internal surface of the inner wall skin, caused by moisture in the building condensing on the cold wall surface.

[0006] It is an aim of certain examples of the present invention to solve, mitigate or obviate, at least partly, at least one of the problems and/or disadvantages associated with the prior art. Certain examples aim to provide at least one of the advantages described below.

BRIEF SUMMARY OF THE INVENTION

[0007] According to a first aspect of the present invention there is provided a roof truss comprising: a bottom chord configured to bear upon and be supported by two spaced apart support structures; at least one top chord connected to the bottom chord and configured to support roofing material on a first side of the bottom chord; and an insulation support frame extending from the bottom chord on a second side of the bottom chord opposite the first side; wherein the insulation support frame is configured to support building insulation on the second side of the bottom chord.

[0008] The roof truss according to the first aspect of the present invention differs from a conventional roof truss in that it includes the insulation support frame. An advantage of the present invention is that because insulation can be installed within the insulation support frame underneath the roof truss (or more precisely, within a void formed by the insulation support frames of a plurality of roof trusses arranged in parallel), insulation may be installed more readily to fill the whole width between support structures (such as building exterior walls) and cold spots may be avoided. Additionally, in some cases where the insulation support frame does not extend across the whole width of the building, the insulation support frame may be configured so that insulation within the frame can provide the same degree of thermal insulation as alternative insulation materials in other portions of the building. In some cases where the support structures comprise insulated wall structures, for instance comprising Structural Insulated Panels (SIPs) the insulation support frame may be configured so that the degree of thermal insulation of insulation material to be installed within the frame will match the thermal insulation provided by the insulated wall structures. Consequently, where the insulation support frame extends up to or connects with the insulated wall structure, continuous thermal insulation can be provided to the upper storey of the building over the walls and the ceiling.

[0009] The bottom chord may have a first end and a second end. The insulation support frame may have a first end and a second end.

[0010] The first end of the insulation support frame may be spaced inwardly from the first end of the bottom chord. The first end of the insulation support frame may be configured, in use, to extend below an upper surface of a first one of the support structures. The second end of the insulation support frame may be spaced inwardly from the second end of the bottom chord. The second end of the insulation support frame may be configured, in use, to extend below an upper surface of a second one of the support structures.

[0011] The bottom chord may comprise a first support surface, which may extend inwardly from its first end. Said first support surface may be configured to abut a first one of the support structures. The bottom chord may comprise a second support surface, which may extend inwardly from its second end. Said second support surface may be configured to abut a second one of the support structures. The insulation support frame first end may be disposed inwardly of the first support surface. The insulation support frame second end may be disposed inwardly of the second support surface.

[0012] The bottom chord may comprise first and second support sections configured to be supported by the two spaced apart support structures and the insulation support frame may extend from the bottom chord between the first and second support sections. In use, the support sections may rest upon and optionally be secured to a wall plate. The support sections may be undifferentiated from other portions of the bottom chord except that they are spaced apart the appropriate distance to align with wall plates mounted upon walls of the building so they can be secured to the wall plates, for instance by nailing. The support sections may be provided proximal to either end of the bottom chord. The support sections may be proximal to the connection between the bottom chord and top chords.

[0013] The insulation support frame may comprise: a ceiling support beam spaced apart from the bottom chord; and a plurality of connecting members, such as legs or arms, connecting the bottom chord and the ceiling support beam. The ceiling support beam and the bottom chord may comprise timber beams or joists generally extending parallel to one another. The primary purpose of the bottom chord is to tie the top chords together at the level of the support structures so that the weight of roofing material does not impart a lateral force to the support structures (such as exterior building walls). In contrast the primary purpose of the ceiling support beam may be to support ceiling material for instance boards (for instance plasterboard) affixed to its underside and to support the weight of insulation within the frame. As such in some examples the ceiling support beam may be formed from a smaller cross section timber. Typically, one leg will be provided at either end of the ceiling support beam. Depending upon the length of the ceiling support beam, one or more intermediate legs may be provided, which may prevent the ceiling support beam bowing.

[0014] The insulation support frame may extend from the bottom chord proximal to at least one end of the bottom chord, and optionally proximal to both ends of the bottom chord. Particularly, the insulation support frame may be configured so that when in use with the support sections supported by building support structures such as exterior walls, the insulation support frame extends to close to or in touch with the support structures to fill the full width of the building.

[0015] In some examples one end of the bottom chord may be spaced apart from the insulation support frame. This may be suitable for a hybrid building including a modular building unit where a portion of the roof truss not including an insulation support frame flies over the top of the modular building unit (and is supported by an exterior building wall outside of the modular building unit, or the modular building unit itself) and the insulation support frame lies between the modular building unit and another wall (typically an exterior wall) of the building. In some cases, a depth of the insulation support frame (defined by the legs and the thickness of the ceiling support beam) is selected so that it matches a depth of ceiling structures within the modular building unit to ensure a uniform ceiling height for rooms within the modular building unit and rooms within the remainder of the building where the insulation support frame is present.

[0016] The top and bottom chords and the insulation support frame may be formed from timber beams. Timber is conventionally used to form roof trusses, however, other materials such as light gauge steel may be used in its place.

[0017] According to a second aspect of the present invention there is provided a building comprising: two spaced apart support structures; and a plurality of roof trusses as defined above; wherein the roof trusses are supported by and span a gap between the two spaced apart support structures to define a roof structure for the building.

[0018] The support structures may comprise building walls, particularly exterior building walls. For the example of a hybrid building comprising at least one modular building unit, one of the support structures may comprise an upper portion of the modular building unit.

[0019] The insulation support frames of the plurality of roof trusses may extend below upper surfaces of the support structures.

[0020] The chords of the roof trusses (e.g. the bottom chords of the plurality of roof trusses) may be arranged in a spaced apart, parallel formation. At least one of the support structures may comprise a load bearing building wall.

[0021] The insulation support frames of the plurality of roof trusses may be filled/ substantially filled with insulation. More precisely, the insulation support frames may align with one another to form a void extending underneath the bottom chords. The undersides of the insulation support frames may be closed off with ceiling material and so define the bottom side of the void and further support insulation material within the void. For instance, a loose fill or rolled insulation material (for instance, rock wool) may be inserted into the void. Insulation supplied in roll form can be unrolled to extend along a space defined between the insulation support frames of adjacent pairs of the roof trusses. The insulation is typically unrolled so that it extends in a direction generally parallel to a main axis of the bottom chords of the adjacent roof trusses, and may naturally extend (once unrolled) laterally into portions of the void defined below the adjacent bottom chords, and/or may be caused to extend into said portions by an installer. In the case of a loose fill insulation, an installer may specifically ensure that the insulation extends into/fills these void portions.

[0022] The insulation support frames of the plurality of roof trusses may further support building services, which may include one or more wire, pipe, or duct. That is, building services may be further provided extending through the void defined by the insulation support frames. Where the building includes one or more modular building units, the void defined by the insulation support frames may be used to route services from a modular building unit into a remainder, or a further part, of the building.

[0023] The insulation support frame may be configured such that the depth of filled insulation provides thermal insulation equivalent to the thermal insulation provided by at least one load bearing wall supporting a bottom chord of a roof truss.

[0024] The building may be a hybrid building comprising: a first building section, the first building section being an on-site construction at a final location for the building; and a second building section comprising one or more modular building units, the first and second building sections being configured to be connected at the final location to form the building.

[0025] At least one roof truss may span only the first building section and may be supported by first and second load bearing walls defining the first building section. The insulation support frame may extend the full width of the bottom chord between the first and second load bearing walls.

[0026] At least one roof truss may span both the first building section and the second building section and may be supported either: by first and second load bearing walls defining the first building section; or by a first load bearing wall defining part of the first building section and a modular building unit.

[0027] For each roof truss spanning part of the first building section and part of the second building the insulation support frame may only extend from the bottom chord within a section spanning the first building section.

[0028] The building may further comprise a roof truss without an insulation support frame spanning only the second building section. Such a roof truss may be a conventional roof truss known in the art.

[0029] Within the first building section a ceiling structure may be secured to the underside of the insulation support frame.

[0030] The insulation support frame may be configured such that a ceiling height within the first building section defined by the ceiling structure is the same as a ceiling height within the second building section defined by a modular building unit.

[0031] Reference is made herein to the widths of certain features, including a width between support structures, a width of the building, and a width of the bottom chord. It will be understood that this should not be considered as limiting on a particular orientation of the features in question within a building. For example, a width between the support structures/width of the building should not be considered as being limited to a frame of reference from a front of the building (in which the width may be taken from a support structure in the form of a left side wall to a support structure in the form of a right side wall). The support structures may be front and back walls of the building, and the width which is referred to may be taken (or may extend) between the front and back walls, in a direction from the front to the back of the building. The width of the bottom chord which is referred to may be a dimension of the bottom chord taken in a direction along the roof truss between the support structures which it spans.

[0032] According to a third aspect of the present invention, there is provided a roof truss comprising: a bottom chord configured to bear upon and be supported by two spaced apart support structures, the bottom chord comprising: a first portion defining a first side of the bottom chord, the first portion comprising a first support surface configured to bear upon a first one of the support structures, and a second support surface configured to bear upon a second one of the support structures; and a second portion extending from the first portion, the second portion defining a second side of the bottom chord which is opposite the first side; and at least one top chord connected to the bottom chord and configured to support roofing material on the first side of the bottom chord; in which the second side is disposed, in use, below the first and second support surfaces of the first portion, and in which the second portion is configured to support ceiling material on the second side.

[0033] In the roof truss of the third aspect, the second side of the bottom chord (which is defined by its second portion) is disposed below the first and second support surfaces defined by its first portion, when the roof truss is positioned on the two spaced apart support structures. It will be understood that, in its use position, the roof truss is generally vertically oriented, with the top chord positioned general ly/largely above the bottom chord (save for any part of the top chord which extends down below its first side). This may provide the benefit that a cavity or space can be created, between adjacent pairs of roof trusses in a roof (and/or between a roof truss and an adjacent support structure, such as a wall of a building), which cavity can accommodate building insulation. The building insulation may effectively be positioned at least partly below upper surfaces of the support structures, upon which the roof truss, specifically its support surfaces, may bear. Where the support structures comprise building insulation (taking the form e.g. of walls of a building), this may provide the benefit that substantially continuous thermal insulation can be provided for the support structures and the ceiling. In particular, thermal insulation in the roof, between adjacent roof trusses, may at least partly overlap building insulation in the support structures, considered in a vertical sense.

[0034] It will be understood that the roof truss of the third aspect may share one or more features with the roof truss of the first aspect. Optional further features of the roof trusses disclosed in this document, and in particular of the roof truss of the third aspect, are as follows.

[0035] The second portion of the bottom chord may extend from the first portion between the first and second support surfaces. The second portion may depend from the first portion, in particular from a bottom of the first portion. The bottom of the first portion may contain, or may be in a same plane as, the first and second support surfaces.

[0036] The first portion may comprise a first end. The first portion may comprise a second end, which may be opposite the first end. The first portion may have a first length. The second portion may have a first end. The second portion may have a second end, which may be opposite the first end. The second portion may have a second length, which may be less than the first length. The first and second ends of the second portion may be spaced apart from the respective first and second ends of the first portion. This may facilitate positioning of the second side of the bottom chord (defined by the second portion) below the first and second support surfaces.

[0037] The bottom chord may comprise first and second support sections, which may respectively define the first and second support surfaces. The first and second support sections may extend beyond respective first and second ends of the second portion.

[0038] The bottom chord may be a unitary, one-piece or substantially single structure, which may define or comprise both the first and second portions. The second portion may extend continuously from the first portion. The bottom chord may take the general form of a beam, joist or similar elongate component, which may define both the first and second portions.

[0039] The first and second portions of the bottom chord may be separate or independent components, and may be connected together to form the bottom chord. The first portion may take the general form of a first beam, joist or similar elongate component. The second portion may take the general form of a second beam, joist or similar elongate component. The first and second beams may be disposed substantially parallel to one another. The second beam may be in contact with the first beam along a majority or all its length.

[0040] The first support surface may be disposed towards the first end of the first portion, and may be disposed adjacent the first end. The second support surface may be disposed towards the second end of the first portion, and may be disposed adjacent the second end. The first and second support surfaces may be provided proximal to respective first and second ends of the first portion. The first support surface may extend generally from the first end in a direction along the length of the first portion towards the second portion, optionally towards the first end of the second portion. The second support surface may extend generally from the second end in a direction along the length of the first portion towards the second portion, optionally towards the second end of the second portion. The first and second support surfaces may be generally planar. The first and second support surfaces may extend substantially parallel to a main axis of the bottom chord, and/or may face generally downwardly in use. Where the bottom chord is a unitary structure, it may comprise recesses, cutouts or cutaway sections at or towards its ends, which may define the first and second support surfaces and/or the first and second support sections.

[0041] The second portion may be configured to receive and/or abut building insulation. The building insulation may be locatable between adjacent roof trusses according to the third aspect, forming part of a roof. In a particular example, the building insulation may be locatable between the second portions of the bottom chords of adjacent such roof trusses. The insulation material may be arranged so that, in use, it abuts a second portion of one roof truss bottom chord on one side of the insulation, and a second portion of the adjacent roof truss bottom chord on another side of the insulation. The insulation may be arranged so that it extends substantially continuously between said second portions of the adjacent roof trusses.

[0042] The bottom chord second portion may be arranged so that, in use, at least part of the building insulation is positionable below upper surfaces of the support structures (upon which the first and second support surfaces of the first portion may bear). The bottom chord may comprise a third side disposed transverse to each of the first and second sides, and which may be configured to receive and/or abut building insulation. The second portion may define at least part of the third side. The bottom chord may comprise a fourth side disposed transverse to each of the first and second sides, which may be configured to receive and/or abut building insulation. The fourth side may be disposed substantially parallel to the third side. The second portion may define at least part of the fourth side. The second portion may be configured so that a majority or all of the third side is disposed below, or extends below, upper surfaces of the support structures. The second portion may be configured so that a majority or all of the fourth side is disposed below, or extends below, upper surfaces of the support structures.

[0043] The first and second sides may comprise or define respective first and second side surfaces of the bottom chord. The third side and/or the fourth side may define respective third/fourth side surfaces of the bottom chord. The first, second, third and/or fourth side surfaces may be generally planar. The first and second side surfaces may face in opposite directions. The first and second side surfaces may be generally parallel to one another. The third and fourth side surfaces may face in opposite directions. The third and fourth side surfaces may be generally parallel to one another, and/or may be transverse to (optionally substantially perpendicular to) the first and/or second side surfaces.

[0044] The second portion may define a ceiling support surface configured to support the ceiling material, which may for instance take the form of ceiling boards (for instance plasterboard) affixed to its underside. The ceiling material, for example the boards, may support the weight of insulation material above, between adjacent roof trusses.

[0045] As discussed elsewhere in this document, timber (or timber-based materials) may be a particularly suitable material for forming the roof trusses, in particular its bottom chord, top chord(s) and web(s) of the roof truss. Timber may be a preferred option for reasons including that it has a relatively low thermal conductivity, ranging from perhaps around 0.10W/m.K to around 0.20W/m.K. Insulating materials used in building construction typically have lower thermal conductivity values, for example in the range of about 0.02 to 0.04W/m.K. Examples include mineral wool, polyurethane, and expanded and extruded polystyrene (XPS). In a roof comprising a plurality of roof trusses according to the third aspect, a non-continuous layer of building insulation may be provided above a ceiling supported by the roof trusses (the insulation material positioned between the bottom chords of adjacent trusses, specifically between the second portions of the bottom chords). Accordingly, at least some of the ceiling material may have a second portion of a bottom chord positioned above it, with building insulation disposed to the side or sides of the second portion. Forming the structure from timber, or a timber-based material, may mitigate cold-bridging effects at the point where the ceiling material contacts the roof truss, due to the relatively low thermal conductivity of the timber material. It will be understood though that additional building insulation may be positioned above or over the bottom chord, in order to mitigate against cold-bridging.

[0046] In some cases, the second portion of the bottom chord may not extend across a whole width of a building having a roof comprising a plurality of the roof trusses. One end of the first portion of the bottom chord may be spaced apart from the second portion, considered in a length direction of the bottom chord, for example so that an end of the second portion stops short of, and/or is spaced from, one of the support structures. This may be suitable for a hybrid building including a modular building unit where a section of the roof truss flies over the top of the modular building unit (and is supported by a support structure, e.g. an exterior building wall, outside of the modular building unit, or by the modular building unit itself). The second portion may lie between the modular building unit and another support structure, e.g. an exterior wall of the building. In some cases, a depth of the second portion (in a vertical sense) may be selected so that it matches the depth of ceiling structures within the modular building unit, to ensure a uniform ceiling height for rooms within the modular building unit and rooms within the remainder of the building where the second portion is present.

[0047] Further features of the roof truss of the third aspect may be derived from the text set out elsewhere in this document, particularly in or with respect to the roof truss of the first aspect.

[0048] The insulation support frame forming part of the roof truss of the first aspect may be considered to form the second portion of the bottom chord of the third aspect. In this situation, the roof truss of the third aspect may comprise a bottom chord structure comprising a bottom chord (of the type defined in the first aspect) forming a first portion of the bottom chord structure, and the insulation support frame, which may form the second portion.

[0049] According to a fourth aspect of the present invention, there is provided a roof assembly for a building comprising two spaced apart support structures, the roof assembly comprising a plurality of roof trusses according to the third aspect of the invention, in which: the roof trusses are disposed substantially parallel to one another and spaced apart so that a gap is defined between adjacent roof trusses. Building insulation may be disposed between the second portions of the bottom chords of the adjacent roof trusses, at least part of the building insulation disposed below the first and second support surfaces of the bottom chord first portions. [0050] According to a fifth aspect of the present invention, there is provided a building comprising two spaced apart support structures and a roof assembly according to the fourth aspect of the invention, in which the first and second support surfaces of the bottom chord first portions bear upon upper surfaces of the support structures, and in which at least part of the building insulation is disposed below the upper surfaces of the support structures.

[0051] Further features of the roof assembly of the fourth aspect, and the building of the fifth aspect, may be derived from the text set out elsewhere in this document, particularly in or with respect to the roof truss of the first or the third aspect.

[0052] Further aspects of the invention may provide a method of forming a roof structure for a building, comprising positioning a plurality of roof trusses according to the first aspect and/or the third aspect of the invention on two spaced apart support structures of the building, so that they are supported by the two spaced apart support structures, and arranging the roof trusses so that they span a gap between the two spaced apart support structures to define a roof structure for the building.

[0053] Where the method comprises positioning a plurality of roof trusses according to the first aspect on the support structures, the method may further comprise installing insulation within the insulation support frames underneath the roof trusses (optionally within a void formed by the insulation support frames of the plurality of roof trusses, which may be arranged in parallel).

[0054] Where the method comprises positioning a plurality of roof trusses according to the third aspect on the support structures, the method may further comprise positioning ceiling material on the second sides of the bottom chords of the roof trusses (optionally involving connecting the ceiling material to the second portions of the bottom chords). The method may further comprise installing insulation in a space defined between adjacent roof trusses, the insulation abutting the second portions of the bottom chords of the adjacent roof trusses, and the insulation optionally resting on/supported by the ceiling material.

[0055] Further features of the method may be derived from the text set out elsewhere in this document, particularly in or with respect to any one or more of the first to fifth aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Examples of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is a side view of a roof truss according to an embodiment of the invention;

Figure 2 is a side view of a roof truss according to another embodiment of the invention;

Figure 3 is a cross section view of the roof truss of figure 1 forming part of a hybrid building;

Figure 4 is a cross section view of the roof truss of figure 2 forming part of a hybrid building;

Figure 5 is a partially cut away perspective view of a hybrid building including roof trusses according to figures 1 and 2;

Figure 6 is an enlarged cross section showing the intersection of part of a roof truss according to figure 1 or figure 2 and a supporting wall;

Figure 7 is a side view of a roof truss according to a further embodiment of the invention;

Figure 8 is a side view of a roof truss according to a further embodiment of the invention;

Figure 9 is a partially cut away perspective view of a hybrid building including roof trusses according to figures 7 and 8;

Figure 10 is a cross section view of the hybrid building shown in figure 9, taken in the direction of the line A-A of figure 9;

Figures 11 and 12 are enlarged cross section and isometric views, respectively, of the hybrid building of figure 10 showing a connection between roof trusses and a supporting wall of the building;

Figure 13 is a view of the hybrid building which is similar to figure 9, but showing additional insulation in the building; and

Figure 14 is a side view of part of a roof truss according to a further embodiment of the invention, which is similar to the view of the roof truss in figure 11.

DETAILED DESCRIPTION

[0057] Referring first to figure 1 this illustrates in a side view a roof truss 1 according to a first example of the present invention. The roof truss 1 is shown in a side view, generally in the orientation it would be placed in during construction of a building. The roof truss 1 is formed from timber beams, though other materials may be used where they provide comparable strength and other relevant material properties. The dimensions of the roof truss 1 are context dependent, including taking account of the size of the building, particularly the gap that the roof truss 1 is required to span to form the roof. Furthermore, the dimensions, particularly cross section, of the timber beams forming the roof truss 1 will be dependent on the structural load placed upon the roof truss, particularly the weight of the supported roof structure. The dimensions, geometry (at least in its upper part) and materials forming the roof truss 1 are not germane to the present invention and so will not be further discussed.

[0058] The roof truss 1 comprises a bottom chord 2 (sometimes referred to as a tie beam) configured to bear upon and be supported by two spaced apart support structures. The support structures may be walls, particularly exterior walls, of the building as will be described below. The primary function of the bottom chord 2 is to tie the roof truss 1 together and prevent the weight of the roof displacing the support structures laterally.

[0059] The roof truss 1 further comprises at least one top chord 3 (sometimes referred to as a rafter) connected to the bottom chord 2 and configured to support roofing material on a first (upper) side of the bottom chord 2. In the example of figure 1 the roof truss 1 comprises a pair of top chords 3 forming a double pitched roof shape descending from an apex and connected to either end 44, 45 of the bottom chord 2. The top chords 3 may extend slightly beyond the bottom chord 2 to form a roof overhang. As noted previously, other roof shapes are possible, such as a single pitched roof.

[0060] The roof truss 1 further comprises an insulation support frame 4 extending from the bottom chord 2 on a second (lower) side of the bottom chord 2 opposite the first side. The insulation support frame 4 is configured to support building insulation on the second side of the bottom chord 2. That is, in use, the insulation material frame 4 may be filled (or substantially filled) with insulation underneath the bottom chord 2 (though optionally insulation may be provided additionally over the top of the bottom chord 2). Where the insulation support frame 4 extends up to one or more support structure such as a building wall, this permits insulation to be provided up to and in contact with the wall to provide substantially unbroken insulation extending from the wall to the ceiling of a room underneath the roof truss 1.

[0061] The bottom chord 2 and top chords 3 are interconnected by webs 5 to brace the chords 2, 3. The bottom chord 2 comprises first and second support sections 6 configured to be supported by the two spaced apart support structures. The support sections 6 may be at or close to each end 44, 45 of the bottom chord 2 and configured in use to be seated upon a top surface of a wall, usually an exterior wall, of a building. More particularly, the support sections 6 may be seated upon and secured to a wall plate. In the example of figure 1 the insulation support frame 4 extends from the bottom chord 2 between the first and second support sections 6 such that in use the insulation support frame 4 comes close to or abuts the building walls. That is, during installation of the roof truss 1 , the roof truss 1 is lowered until the support sections 6 contact the top of the wall or the wall plate and the insulation support frame 4 is inserted between upper sections of the walls.

[0062] The insulation support frame 4 comprises a ceiling support beam 7 spaced apart from the bottom chord 2 and a plurality of connecting members, in the form of legs 8, connecting the bottom chord 2 and the ceiling support beam 7. The ceiling support beam 7 extends generally parallel to the bottom chord 2, although this is not essential. In use within a building ceiling material (for instance plasterboard) may be affixed to the underside of the ceiling support beam 7. More particularly, ceiling material will span the undersides of a plurality of insulation support frames 4 forming parts of a plurality of roof trusses 1 defining the shape of the roof. In the example of figure 1 the insulation support frame 4 comprises at least first and second legs 8 located proximal to the ends of the ceiling support beam 7. A third, intermediate leg 8 is also shown, intermediate legs being used where the length of the insulation support frame requires bracing to avoid bowing.

[0063] The insulation support frame 4 defines a void 9. Where a roof is constructed from a plurality of roof trusses 1 the void 9 extends continuously through adjacent roof trusses. The lower side of the void 9 may be further defined by ceiling material affixed to the underside of the ceiling support beam 8. Sides of the void 9 at either end of the insulation support frame 4 may be open, though in use closed off by the walls or other structures supporting the support sections 6.

[0064] As noted above, suitably the roof truss 1 including the insulation support frame 4 may be formed from timber. Nodes where the components of the roof truss 1 connect may be connected through nail plates (not illustrated) comprising a metal plate spanning a node through which a plurality of nails or other fixings may be passed into the timber. Roof truss 1 comprises a premanufactured product in that it may be manufactured away from a building site, typically in a factory, and delivered to the building site as a modular building component. Advantageously, this allows for a plurality of roof trusses to be provided that are closely aligned in dimensions. These may be manufactured to fit a specific building under construction. Alternatively, buildings may be designed so that the gap between exterior walls for an uppermost storey of the building matches the spacing between roof truss support sections.

[0065] Referring now to figure 2, a second example of a roof truss 11 is shown. Roof truss 11 is generally similar to roof truss 1 except where noted below and so the same reference numbers are used for corresponding parts, incremented by 10. For roof truss 11 the conventional upper structure comprising bottom chord 12, top chords 13 and webs 15 is the same as for roof truss 1. Furthermore, the bottom chord 12 includes corresponding first and second support sections 16 located at either end close to where the bottom chord 12 intersects the top chords 13.

[0066] Differing from roof truss 1 of figure 1 , for roof truss 11 of figure 2 the insulation support frame 14 is shorter. The ceiling support beam 17 extends from proximal to or immediately adjacent to one of the support sections 16 (on the right in figure 2) to only part way along the bottom chord 12. In figure 2 the insulation support frame 14 extends for slightly more than one third of the length of the bottom chord 12, however there is no restriction to the exact proportion of the bottom chord 12 corresponding to the insulation support frame 14. Similarly, the void 19 is shorter than for void 9 of roof truss 1. Figure 2 shows the insulation support frame 14 including only first and second legs 18 at either end of the ceiling support beam 17. However, in some cases one or more intermediate support legs 18 may be provided as for the example of figure 1.

[0067] Roof trusses according to the examples of figures 1 and 2 are suitable for forming the structure of pitched rooves for any type of building. Roof trusses are conventionally used for forming pitched rooves for residential buildings, including detached, semi-detached, or terraced houses, however the present invention is not limited to any particular type of building use or configuration. Furthermore, roof trusses according to the present invention may be suitably used for any building construction type, including buildings for which the structure of the building is constructed on-site. There is no limitation to the type of wall structure that is to be used in combination with the roof trusses, so long as it is suitable for supporting the bottom chord at the point on the support section. Indeed, the roof trusses being supported by walls (particularly exterior walls) is the most usual scenario, though other portions of a building may comprise a support structure. As examples, exterior walls where they support roof trusses may be formed from bricks or blocks, cementitious materials (including where this is 3D printed), timber studs, timber panels (including SIPs), light gauge steel studs, or any other known techniques.

[0068] As an alternative to buildings constructed fully on-site (that is, at the building site or final location of the building), prefabricated buildings (also known as ‘modular’ buildings) are well known in the construction industry, particularly modular residential buildings such as houses, flats or apartments, and hotels. Roof trusses according to the present invention may be used to form the roof structure of a modular building. Modular buildings typically comprise a series of modular building units which are constructed in a factory, transported to a final location (or site) for the building, and then arranged in a predetermined configuration and coupled together to form the finished building. The modular building units are typically constructed in the factory to a substantially assembled form in which they can be transported to the final location. Construction of the building can involve stacking one or more upper modular building unit on a lower such unit, so that the upper unit is supported by the lower unit. Modular building units can also be arranged side by side.

[0069] Hybrid buildings have been developed by the applicant which comprise a first building section that is constructed at a final location for the building and a second building section comprising one or more modular building units constructed in a dedicated facility, away from the final location. A hybrid building of this type can provide advantages including that: construction of the first building section is simplified, with more complex parts of the building provided in the section formed by the modular building unit (or multiple modular building units); and the first building section can provide the primary living space in the building, without being constrained by construction and transport limitations imposed on the modular building unit(s). The hybrid buildings and associated construction techniques are disclosed in International patent publication nos. WO2022/243696, WO2022/243695, WO2022/243694, WO2022/243693, and WO2023/222853, the disclosures of which are incorporated herein by this reference.

[0070] The applicant has identified that roof trusses in accordance with figures 1 and 2 may be particularly suited to forming the roof structure of a hybrid building in which the pitched roof extends over both the first and second building sections. An example of this will now be presented in connection with figures 3 to 6.

[0071] In principle the roof trusses may be constructed so that where a roof truss extends between first and second exterior building walls and spans only over the first (onsite constructed) building section, a roof truss 1 according to figure 1 is used so that the insulation support frame 4 extends fully between exterior walls of the building. Elsewhere within the same pitched roof, where a roof truss spans both the first building section and the second (modular) building section, a roof truss 11 according to figure 2 is used so that the insulation support frame 14 extends between an exterior building wall defining one side of the first building section and a modular building unit forming part of the second building section.

[0072] Figures 3 and 4 show different cross sections of a hybrid building 30. The cross sections are taken in a vertical plane through the hybrid building and the cross sections are offset from one another along a horizontal axis (extending into the page) so that the cross section of figure 3 shows a roof truss 1 according to figure 1 spanning only a first (on-site constructed) building section 31 , while the cross section of figure 4 shows a roof truss 11 according to figure 2 spanning a first building section 31 and a second (modular) building section 40 comprising a modular building unit 41 (shown here as a framework which forms a cuboid shape).

[0073] It can be seen in figure 3 that the support sections 6 of roof truss 1 rest upon wall plates 32 which in turn are secured to the tops of walls 33, walls 33 being the exterior walls of the building. Insulation support frame 4 extends the full width of the building within the first building section 31 between the exterior walls 33 of the building 30. Consequently, thermal insulation can be fitted within the insulation support frame 4 across the full width of the first building section 31 between the exterior walls 33.

[0074] Similarly, figure 4 shows that the support sections 16 of roof truss 11 rest upon wall plates 32 which in turn are secured to the tops of walls 33, walls 33 being the same exterior walls of the building 30 as shown in figure 3, only offset along an axis extending into the page to a point where modular building unit 41 is present. Insulation support frame 14 extends only across the width of the first building section 31 between the right hand exterior wall 33 and the modular building unit 41. Consequently, thermal insulation can be fitted within the insulation support frame 4 across the full width of the first building section 31. Meanwhile, over the second building section 40 the roof truss 11 doesn’t include an insulation support frame. In some cases, the bottom chord 12 passes over the modular building unit 41 without resting upon it. In other cases, the bottom chord 12 may be partially or fully supported by the modular building unit 41 (as well as or instead of the left hand exterior wall 33).

[0075] Meanwhile, the modular building unit 41 includes a ceiling assembly 42 which is relatively deep (optionally this providing space for the installation of building services). As illustrated in figure 4, the insulation support frame 14 of roof truss 11 may be configured (particularly through the construction of the legs) such that it is aligned in depth to the ceiling assembly 42 of modular building unit 41. As such the ceiling height within building rooms in the first and second building sections 31 , 40 may be the same.

[0076] The modular building unit 41, particularly the ceiling assembly 42, may include thermal insulation. In one example the ceiling assembly 42 may including a cavity containing building services such as wires, ducts, and pipes (not illustrated in figure 4) over which is provided a layer of insulation 43, which may suitably be a SIP. A SIP provides a defined degree of thermal insulation. It may be a relatively high degree of insulation per unit thickness. The insulation within void 19 of the insulation support frame 14 may be chosen so that it provides a comparable degree of thermal insulation to that provided within the modular building unit ceiling assembly 42. Owing to the greater depth of the insulation support frame 14 relative to modular building unit insulation layer 43, it may be that a less thermally efficient but cheaper grade of insulation may be used, for instance rock wool. The result is that within rooms defined by the first and second building sections 31, 40 a uniform layer of ceiling insulation is provided. Similarly, walls 33 may be formed from an insulating material such as SIPs such that an unbroken and generally similar layer of insulation is provided around and over the rooms in the first and second building sections.

[0077] Referring back to figure 1 , as discussed above, the bottom chord 2 of the roof truss 1 has ends 44 and 45. The end 44 may be considered to be a first end, and the end 45 a second end. The insulation support frame 4 similarly has a first end 46 and a second end 47. The first end 46 of the insulation support frame 4 is spaced inwardly from the first end 44 of the bottom chord 2, and is configured, in use, to extend below an upper surface of a first one of the support structures. In the example of figure 3, the support structures are the walls 33, the wall plates 32 defining such upper surfaces 48. The first end 46 of the insulation support frame 4 therefore extends below the upper surface 48 of the wall plate 32 on the left hand wall 33 shown in the drawing. The second end 47 of the insulation support frame 4 is similarly spaced inwardly from the second end 45 of the bottom chord 4, and is configured, in use, to extend below the upper surface of a second one of the support structures. The second end 47 of the insulation support frame 4 therefore extends below the upper surface 48 of the wall plate 32 on the right hand wall 33 shown in figure 3.

[0078] The bottom chord 4 also comprises a first support surface 50, which is effectively provided by the support section 6 at the first end 44. The first support surface 50 extends inwardly from the first end 44, and is configured to abut the left wall 33. The bottom chord 4 additionally comprises a second support surface 52, which is effectively provided by the support section 6 at the second end 45. The second support surface 50 extends inwardly from the second end 45, and is configured to abut the right wall 33. The insulation support frame first end 46 is effectively disposed inwardly of the first support surface 50, and the insulation support frame second end 47 is disposed inwardly of the second support surface 52.

[0079] Turning now to figure 5, this shows in a partially cutaway perspective view hybrid building 30 including the modular building unit 41 in one corner (defining the first building section 40) with the second building section 30 surrounding the modular building unit 41 in an L-shape. Exterior walls 33 are shown on two sides forming spaced apart support structures. A plurality of roof trusses 1 and 11 are shown, selected, and positioned according to whether they span both building sections 31 ,

40 or only the first building section 31. It can be seen in figure 5 how the plurality of roof trusses 1 , 11 define the shape of the pitched roof. Roofing material (not illustrated) will be applied to the top chords of the roof trusses 1 , 11 in a conventional fashion. The roof trusses are arranged in parallel, spaced apart formation. Insulation support frames 4, 14 extend below the upper surfaces of the walls 33 within the first building section. It will be understood that the bottom chords 2,12, top chords 3, 13 and webs 5, 15 will be connected by timber bracing know as runners extending between the trusses 1 , 11. Although not illustrated in figure 5, it will be understood that within the first building section 31 the undersides of the insulation support frames 4, 14 will be boarded out with ceiling material extending up to and typically sealed to the exterior walls 33 and the modular building unit 41 and the void 9, 19 filled within insulation. In some cases, building services including one or more wire, pipe, or duct may also extend within the insulation support frame void 9, 19. The building services may also connect through to services within the ceiling assembly 42 of the modular building unit 41. Exemplary such building services are shown schematically in the drawing, and indicated by numerals 54 and 56. Insulation 43 overlying the modular building unit

41 is also visible in figure 5.

[0080] Figure 6 shows in an enlarged cross section part of roof truss 1 (though equally it may be a roof truss 11) where it engages wall plate 32 of exterior wall 33. Insulation support frame 4, particularly ceiling support beam 7, is shown supporting ceiling material 60, for instance a sheet of plasterboard. Insulation 61 such as rock wool is shown filling void 9.

[0081] Referring now to figure 7, a third example of a roof truss 101 is shown. Roof truss 101 is generally similar to roof truss 1 except where noted below and so the same reference numbers are used for corresponding parts, incremented by 100.

[0082] The roof truss 101 comprises a bottom chord 102 configured to bear upon and be supported by two spaced apart support structures, which can be the exterior walls 33 of the hybrid building 30 shown in figures 3 and 4. The roof truss 101 also comprises at least one top chord connected to the bottom chord, and in the illustrated example comprises two top chords 103, similar to the roof truss 3 of figure 1. The bottom chord 102 and top chords 103 are interconnected by webs 105, in a similar way to the roof truss 3.

[0083] The bottom chord 102 comprises a first portion 158 defining a first side 159 of the bottom chord, the first portion comprising a first support surface 150 configured to bear upon a first one of the walls 33, and a second support surface 152 configured to bear upon a second one of the walls 33. The bottom chord 102 also comprises a second portion 162 extending from the first portion 158, the second portion defining a second side 163 of the bottom chord which is opposite the first side 159. The top chords 103 are again configured to support roofing material (not shown), on the first side 159 of the bottom chord 102. The second portion 162 of the bottom chord 102 is configured to support ceiling material (not shown in figure 7) on the second side 163.

[0084] The second side 163 of the bottom chord 102 (which is defined by its second portion 162) is disposed below the first and second support surfaces 150 and 152 defined by its first portion 158, when the roof truss 101 is positioned on the two spaced apart walls 33. In this use position of the roof truss 103, the truss is generally vertically oriented, with the top chords 103 positioned above the bottom chord 102 (save for any parts of the top chords 103 which extend down below the first side 159, e.g. at eave regions of a roof comprising the truss). As will be described in more detail below, this may provide the benefit that a cavity or space can be created, between adjacent pairs of roof trusses in a roof comprising a plurality of the trusses 101 (and/or between a roof truss and an adjacent support structure, such as a wall of a building), which cavity can accommodate building insulation.

[0085] As can be seen in figure 7, the second portion 162 of the bottom chord 102 extends from its first portion 158 between the first and second support surfaces 150 and 152. The second portion 162 depends from the first portion 158, in particular from a bottom 164 of the first portion. The bottom 164 of the first portion 158 contains and/or is in the same plane as the first and second support surfaces 150 and 152.

[0086] The first portion 158 of the bottom chord 102 comprise a first end 144, a second opposite end 145, and has a first length. The second portion 162 has a first end 146, a second opposite end 147, and has a second length, which is less than the first length of the first portion 158. The first and second ends 146, 147 of the second portion 162 are spaced apart from the respective first and second ends

144, 145 of the first portion 158. This facilitates positioning of the second side 163 of the bottom chord 102 (defined by the second portion 162) below the first and second support surfaces 150 and 152. The first portion 158 of the bottom chord 102 effectively comprises support sections 106 at its first and second ends 144 and

145, which define the first and second support surfaces 150 and 152. The support sections 106 extend beyond the respective first and second ends 150, 152 of the second portion 162.

[0087] In the illustrated embodiment, the first and second portions 158 and 162 of the bottom chord 102 are provided as or defined by separate/independent components, and are connected to one another to form the bottom chord. The first portion 158 takes the general form of a first beam, joist or similar elongate component. The second portion 162 takes the general form of a second beam, joist or similar elongate component. The first and second beams forming the sections 158 and 162 are disposed substantially parallel to one another, and the second beam is in contact with the first beam along a majority or all its length. Connection can be by mechanical fixings (e.g. nails, screws, bolts, and/or in conjunction with joining plates, which will be discussed below), by bonding (e.g. using an adhesive) or combinations of these options.

[0088] The first support surface 150 is disposed towards the first end of the first portion 158, adjacent the first end 144, and the second support surface 152 is disposed towards the second end of the first portion, adjacent the second end 145. The first support surface 150 extends generally from the first end 144 in a direction along the length of the first portion towards the first end 146 of the second portion 162. Similarly, the second support surface 152 extends generally from the second end 145 in a direction along the length of the first portion towards the second end 147 of the second portion 162. The first and second support surfaces 150 and 152 are generally planar, extending substantially parallel to a main axis 162 of the bottom chord 102, and face generally downwardly in use for abutting e.g. the walls 33.

[0089] Referring now to figure 8, a fourth example of a roof truss 201 is shown. Roof truss 201 is generally similar to roof truss 1 except where noted below and so the same reference numbers are used for corresponding parts, incremented by 200. The roof truss 201 is effectively a variation on the roof truss 101 shown in figure 7, in the same way as the roof truss 11 is a variation of the roof truss 1. The roof truss 201 therefore differs from roof truss 101 of figure 7 in that it comprises a bottom chord 202 comprising a second portion 262 which is shorter than that in the roof truss 101. The roof truss 201 has a use in a hybrid building of the type discussed above, in which the truss bridges across a modular building unit forming part of the building. This is shown in figure 9, which is a partially cut away perspective view of the hybrid building 30 discussed above, but including roof trusses 101 and 201 according to figures 7 and 8. Roof trusses 101 span the first building section 31, whilst roof trusses 201 extend between (and are supported by) the right side wall 33 and the modular building unit 41 forming the second (modular) building section 40. Figure 10 is also referred to, which is a cross section view of the hybrid building shown in figure 9, taken in the direction of the line A-A.

[0090] As discussed above, adjacent trusses in the roof of the building 30 can accommodate insulation. Figure 9 shows insulation 161 located in a cavity, space or gap 166 between the second portions 162 of the bottom chords 102 of each adjacent pair of the roof trusses 101 . The insulation 161 spans the gap 166, extending substantially continuously between the second portions 162 of the adjacent roof trusses 101 . The insulation 161 is effectively positioned at least partly below the upper surfaces 48 of the walls 33 (per figure 3, defined by the wall plates 32) upon which the roof trusses 101 bear. This provides substantially continuous thermal insulation for the support structures and the ceiling as discussed above, the thermal insulation 161 in the roof at least partly overlapping building insulation in the walls, considered in a vertical sense. The insulation 161 , which will typically be of a mineral wool or similar material as discussed above, extends along the trusses 101 between the building side walls 33. Only a portion of the insulation material is shown in figure 9 so that a relationship between the modular building unit 41 and the trusses 101 can be better seen.

[0091] This is better illustrated in figures 11 and 12, which are enlarged cross section and isometric views, respectively, of the hybrid building of figure 10 showing a connection between the roof trusses 101 and the left side supporting wall 33. These drawings show a variation in the wall structure, which is formed in this example as a cavity wall structure comprising an inner load-bearing wall layer 167, an outer wall layer 168, and a cavity 169 between the inner and outer wall layers which contains insulation 170. The inner and outer wall layers 167 and 168 can be of any suitable material, and may e.g. be masonry such as breeze or cinder blocks (for the inner layer 167), and bricks or other decorative blocks (for the outer layer 168). The drawings also show a connecting plate 175 used to join the first and second portions 158 and 162 of the bottom chord 102 (using fixings such as nails passing through the plate into the portions). A similar connecting plate 176 is used to join the upper chord 103 to the webs 105, and a connecting plate 177 joins the bottom chord 102 to the upper chord 103.

[0092] It can be seen that there is a vertical overlap between the second portion 162 of the truss bottom chord 102 and the wall insulation 170 (and thus between insulation

161 disposed between the second portions of bottom chord of adjacent trusses). The roof trusses 202 similarly support insulation 261 between adjacent trusses, but this extends only part way across the width of the building 30, up to the modular building unit 40 (whose ceiling structure supports insulation 43, as discussed above).

[0093] Referring particularly to figure 12, it can be seen that the bottom chord 102 of the truss 101 comprises a third side 171, and a fourth side 172 which is substantially parallel to the third side. The third and fourth sides 171 and 172 are each disposed transverse (typically substantially perpendicular) to the first and second sides 159 and 163, facing adjacent trusses in the roof, and abut the building insulation 161 . The third and fourth sides 171 and 172 are defined at least partly by the second portion 162 of the bottom chord 102, and in the illustrated example, are defined jointly by the first and second portions 158 and 162. The bottom chord 102 may be configured, by appropriate dimensioning of structural features (in particular the second portion 162), so that a majority or all of the third and fourth sides 171 and 172 are disposed below, or extend below, the upper support surfaces 48 of the walls 33 (defined by the wall plates 32).

[0094] Timber (or timber-based materials) may be a particularly suitable material for forming the bottom chord 102, the top chords 103, and/or the webs 105 of the roof truss 101. This may apply also to the roof truss 201 , and of course the roof trusses 1 and 11. Timber may be a preferred option for reasons including that it has a relatively low thermal conductivity, ranging from perhaps around O.WW/m.K to around 0.20W/m.K. Insulating materials used in building construction typically have lower thermal conductivity values, for example in the range of about 0.02 to 0.04W/m.K. Examples include mineral wool, polyurethane, and expanded and extruded polystyrene (XPS). In a roof comprising a plurality of the roof trusses 101 , a non-continuous layer of building insulation may be provided above a ceiling supported by the roof trusses (the insulation material positioned between the bottom chords 102 of adjacent trusses, specifically between the second portions

162 of these structures). Ceiling material (e g. the ceiling material 60 shown in figure 6) has the second portions 162 of the bottom chords 102 of trusses 101 positioned above it. Forming the structure from timber, or a timber-based material, may resist cold-bridging at the point where the ceiling material contacts the roof trusses, due to the relatively low thermal conductivity of the timber material.

[0095] It will be understood however that additional building insulation may be positioned above or over the bottom chords of the trusses, in order to mitigate against coldbridging. This is shown in figure 13, which is a view of the building 30 similar to figure 9, but showing such additional insulation 173 positioned between roof trusses 201 . The insulation 173 may be deeper in the portion of the building defined by the first building section 31 , compared to the portion where the roof trusses 201 bridge over the modular building unit 41. In a variation, a double layer of insulation (not shown) may be provided in the portion of the building defined by the first building section 31 , an upper layer being positioned on a lower layer defined by the insulation 161/261.

[0096] Turning now to figure 14, there is shown a side view of part of a roof truss 301 according to a further example, which is similar to the view of the roof truss 101 in figure 11. Again, roof truss 301 is generally similar to roof truss 1 except where noted below and so the same reference numbers are used for corresponding parts, incremented by 300.

[0097] In this example, the roof truss 301 is essentially the same as the roof truss 101 , except that a bottom chord 302 of the roof truss 301 is a unitary, one-piece or substantially single structure, which defines or comprises both a first portion 358 and a second portion 362. The bottom chord 302 takes the general form of a beam, joist or similar elongate component, which defines both the first and second portions 358 and 362. Recesses, cutouts or cutaway sections at or towards its ends define first and second support surfaces, and/or the first and second support sections. The drawing shows a first end 344, with a cutaway section 306 which defines the support section, and a support surface 350. It will be understood that this can also apply to the truss 201, which may similarly have a bottom chord 202 which is unitary or one-piece.

[0098] The present invention extends to methods of forming a roof structure for a building, comprising positioning a plurality of the roof trusses according to any of the above examples on two spaced apart support structures of a building, so that they are supported by the two spaced apart support structures. The roof trusses are arranged so that they span a gap between the two spaced apart support structures to define a roof structure for the building. The method may employ a plurality of the roof trusses 1 and/or 11 , and may further comprise installing the insulation 61 within the insulation support frames 4/14 underneath the roof trusses (within/extending into the void 9/19 formed by the insulation support frames of the plurality of roof trusses). The method may employ a plurality of the roof trusses 101 , 201 and/or 301 , and may further comprise positioning ceiling material on the second sides of the bottom chords 102, 202, 302 of the roof trusses (optionally involving connecting the ceiling material to the second portions of the bottom chords). Insulation material may be positioned on the ceiling material as discussed above. Further features of the methods will be evident from the description above. [0099] Throughout this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components, integers, or steps. Throughout this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Throughout this specification, the term “about” is used to provide flexibility to a range endpoint by providing that a given value may be “a little above” or “a little below” the endpoint. The degree of flexibility of this term can be dictated by the particular variable and can be determined based on experience and the associated description herein.

[00100] Features, integers, or characteristics described in conjunction with a particular aspect or example of the invention are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification, and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing examples. The invention extends to any novel feature or combination of features disclosed in this specification. It will also be appreciated that, throughout this specification, language in the general form of “X for Y” (where Y is some action, activity or step and X is some means for carrying out that action, activity or step) encompasses means X adapted or arranged specifically, but not exclusively, to do Y.

[00101] Each feature disclosed in this specification may be replaced by alternative features serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[00102] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS:

1. A roof truss comprising: a bottom chord configured to bear upon and be supported by two spaced apart support structures; at least one top chord connected to the bottom chord and configured to support roofing material on a first side of the bottom chord; and an insulation support frame extending from the bottom chord on a second side of the bottom chord opposite the first side; wherein the insulation support frame is configured to support building insulation on the second side of the bottom chord.

2. A roof truss as claimed in claim 1, wherein: the bottom chord has a first end and a second end; the insulation support frame has a first end and a second end; the first end of the insulation support frame is spaced inwardly from the first end of the bottom chord and configured, in use, to extend below an upper surface of a first one of the support structures; and the second end of the insulation support frame is spaced inwardly from the second end of the bottom chord and configured, in use, to extend below an upper surface of a second one of the support structures.

3. A roof truss as claimed in claim 1 , wherein: the bottom chord comprises a first end, and a first support surface extending inwardly from the first end and configured to abut a first one of the support structures; the bottom chord comprises a second end, and a second support surface extending inwardly from the second end and configured to abut a second one of the support structures; and the insulation support frame has a first end disposed inwardly of the first support surface, and a second end disposed inwardly of the second support surface.

4. A roof truss according to claim 1 , wherein the bottom chord comprises first and second support sections configured to be supported by the two spaced apart support structures and the insulation support frame extends from the bottom chord between the first and second support sections.

5. A roof truss according to any preceding claim, wherein the insulation support frame comprises: a ceiling support beam spaced apart from the bottom chord; and a plurality of legs connecting the bottom chord and the ceiling support beam.

6. A roof truss according to claim 5, wherein the ceiling support beam extends generally parallel to the bottom chord.

7. A roof truss according to claim 5 or claim 6, wherein the insulation support frame comprises at least first and second legs located proximal to the ends of the ceiling support beam.

8. A roof truss according to any one of the preceding claims, wherein the insulation support frame extends from the bottom chord proximal to at least one end of the bottom chord.

9. A roof truss according to claim 8, wherein one end of the bottom chord is spaced apart from the insulation support frame.

10. A roof truss according to any one of the preceding claims, wherein the top and bottom chords and the insulation support frame are formed from timber beams.

11. A building comprising: two spaced apart support structures; and a plurality of roof trusses according to any one of the preceding claims; wherein the roof trusses are supported by and span a gap between the two spaced apart support structures to define a roof structure for the building.

12. A building according to claim 11 , wherein the insulation support frames of the plurality of roof trusses extend below upper surfaces of the support structures.

13. A building according to claim 11 or claim 12, wherein the chords of the roof trusses are arranged in a spaced apart, parallel formation.

14. A building according to any one of claims 11 to 13, wherein at least one of the support structures comprises a load bearing building wall.

15. A building according to any one of claims 11 to 14, wherein the insulation support frames of the plurality of roof trusses are filled with insulation.

16. A building according to claim 15, wherein the insulation support frames of the plurality of roof trusses further support building services including one or more wire, pipe, or duct.

17. A building according to claim 15 or claim 16, wherein the insulation support frame is configured such that the depth of filled insulation provides thermal insulation equivalent to the thermal insulation provided by at least one load bearing wall supporting a bottom chord of a roof truss.

18. A building according to any one of claims 11 to 17, wherein the building is a hybrid building comprising: a first building section, the first building section being an on-site construction at a final location for the building; and a second building section comprising one or more modular building units, the first and second building sections being configured to be connected at the final location to form the building.

19. A building according to claim 18, wherein at least one roof truss spans only the first building section and is supported by first and second load bearing walls defining the first building section.

20. A building according to claim 18 or claim 19, wherein at least one roof truss spans both the first building section and the second building section and is supported either: by first and second load bearing walls defining the first building section; or by a first load bearing wall defining part of the first building section and a modular building unit.

21. A building according to claim 20, wherein for each roof truss spanning part of the first building section and part of the second building the insulation support frame only extends from the bottom chord within the section spanning the first building section.

22. A building according to any one of claims 18 to 21 , further comprising a roof truss without an insulation support frame spanning only the second building section.

23. A building according to any one of claims 18 to 22, wherein within the first building section a ceiling structure is secured to the underside of the insulation support frame.

24. A building according to claim 23, wherein the insulation support frame is configured such that a ceiling height within the first building section defined by the ceiling structure is the same as a ceiling height within the second building section defined by a modular building unit.

25. A roof truss comprising: a bottom chord configured to bear upon and be supported by two spaced apart support structures, the bottom chord comprising: a first portion defining a first side of the bottom chord, the first portion comprising a first support surface configured to bear upon a first one of the support structures, and a second support surface configured to bear upon a second one of the support structures; and a second portion extending from the first portion, the second portion defining a second side of the bottom chord which is opposite the first side; and at least one top chord connected to the bottom chord and configured to support roofing material on the first side of the bottom chord; in which the second side is disposed, in use, below the first and second support surfaces of the first portion, and in which the second portion is configured to support ceiling material on the second side.

26. A roof truss as claimed in claim 25, in which the second portion of the bottom chord extends from the first portion between the first and second support surfaces.

27. A roof truss as claimed in either of claims 25 or 26, in which the second portion depends from a bottom of the first portion, the bottom being in a plane containing the first and second support surfaces.

28. A roof truss as claimed in any one of claims 25 to 27, in which: the first portion comprises a first end, a second end opposite the first end, and a first length; the second portion has a first end, a second end opposite the first end, and a second length which is less than the first length; and the first and second ends of the second portion are spaced apart from the respective first and second ends of the first portion.

29. A roof truss as claimed in any one of claims 25 to 28, in which the bottom chord comprises first and second support sections defining the respective first and second support surfaces, and in which the first and second support sections extend beyond respective first and second ends of the second portion.

30. A roof truss as claimed in any one of claims 25 to 29, in which the bottom chord is a unitary structure defining both the first and second portions, and the second portion extends continuously from the first portion.

31. A roof truss as claimed in any one of claims 25 to 30, in which the first and second portions of the bottom chord are separate components that are connected together to form the bottom chord.

32. A roof truss as claimed in claim 31, in which the first portion takes the form of a first beam and the second portion takes the form of a second beam, the first and second beams disposed substantially parallel to one another and the second beam being in contact with the first beam along its length.

33. A roof truss as claimed in any one of claims 25 to 32, in which the first and second support surfaces are provided proximal to respective first and second ends of the first portion, the first support surface extending from the first end in a direction along the length of the first portion towards a first end of the second portion, and the second support surface extending from the second end in a direction along the length of the first portion towards the second end of the second portion.

34. A roof truss as claimed in claim 33, in which the bottom chord is a unitary structure defining both the first and second portions, and comprises recesses towards its ends which define the first and second support surfaces.

35. A building comprising: two spaced apart support structures; and a plurality of roof trusses according to any one of claims 25 to 34; wherein the roof trusses are supported by and span a gap between the two spaced apart support structures to define a roof structure for the building.

36. A building according to claim 35, wherein the second portions of the roof truss bottom chords extend below upper surfaces of the support structures.

37. A building according to claim 35 or claim 36, wherein the chords of the roof trusses are arranged in a spaced apart, parallel formation.

38. A building according to any one of claims 35 to 37, wherein at least one of the support structures comprises a load bearing building wall.

39. A building according to any one of claims 35 to 38, wherein the building is a hybrid building comprising: a first building section, the first building section being an on-site construction at a final location for the building; and a second building section comprising one or more modular building units, the first and second building sections being configured to be connected at the final location to form the building.

40. A building according to claim 39, wherein at least one roof truss spans only the first building section and is supported by first and second load bearing walls defining the first building section.

41. A building according to claim 39 or claim 40, wherein at least one roof truss spans both the first building section and the second building section and is supported either: by first and second load bearing walls defining the first building section; or by a first load bearing wall defining part of the first building section and a modular building unit.

42. A building according to claim 41 , wherein for each roof truss spanning part of the first building section and part of the second building, the second portion only extends from the first portion of the bottom chord within the section spanning the first building section.

43. A building according to any one of claims 35 to 42, wherein within the first building section a ceiling structure is secured to the underside of the second portions of the roof truss bottom chords.

44. A building according to claim 43, wherein the second portions of the roof truss bottom chords are configured such that a ceiling height within the first building section defined by the ceiling structure is the same as a ceiling height within the second building section defined by a modular building unit.

45. A building according to any one of claims 35 to 44, in which building insulation is located between the second portions of adjacent roof truss bottom chords, the insulation arranged so that it abuts a second portion of one roof truss on one side of the insulation, and a second portion of the adjacent roof truss on another side of the insulation.

46. A building according to claim 45, in which the second portions of the roof truss bottom chords are arranged so that at least part of the building insulation is positioned below upper surfaces of the support structures.

47. A method of forming a roof structure for a building, comprising positioning a plurality of roof trusses according to any one of claims 25 to 34 on two spaced apart support structures of the building, so that they are supported by the two spaced apart support structures, and arranging the roof trusses so that they span a gap between the two spaced apart support structures to define a roof structure for the building.

48. A method as claimed in claim 47, comprising positioning ceiling material on the second sides of the bottom chords of the roof trusses, and installing insulation in a space defined between adjacent roof trusses, the insulation abutting the second portions of the bottom chords of the adjacent roof truss bottom chords.