GB2240153A

GB2240153A - Affixing of roof coverings to support slabs

Info

Publication number: GB2240153A
Application number: GB9026805A
Authority: GB
Inventors: Harald Kittilsen; John Willy Johansen
Original assignee: Isola Fabrikker AS
Current assignee: Isola Fabrikker AS
Priority date: 1990-01-17
Filing date: 1990-12-10
Publication date: 1991-07-24
Anticipated expiration: 2010-12-10
Also published as: GB2240153B; DE4101133C2; NO900245D0; DE4101133A1; NO900245L; GB9026805D0; NO168845C; NO168845B

Abstract

The affixing of a roof covering to a wood wool cement slab (30) is effected by providing a blind recess (34), introducing into said recess (34) an expandable, preferably bondable material (35) for the expansion into said recess (34) and into the slab cavities (32) in the immediate proximity of said recess (34), inserting a fastener (33) into said filled recess (34) before the material (35) is cured or expanded. and allowing the fastener (33) to be cured into said expandable material (35) for affixing a roof covering to the wood wool cement slabs (30). <IMAGE>

Description

1 1

Field of the invention

The present invention concerns a method related to the affixing to a support, especially the affixing of a roof covering to a so- called wood wool cement slab, which comprises substantially flat wood wool fibres in mixture with a cured cement mortar.

The invention also pertains to a device to be used in connection with the affixing to such a support, i.e. especially for the affixing of a roof covering to a roof decking comprising wood wool cement slabs.

is Backqround of the invention So-called wood wool cement slabs, comprising substantially flat wood wool fibres in a mixture with cured cement mortar, are usually marketed as rectangular, thin slabs, and are characterized by being relatively light, and having favourable thermal, fire protecting and acoustic properties: Such slabs are therefore used as structure elements in various connections, somewhat in dependence of the geographic relations. In Norway such wood wool cement slabs are used as inner casting slabs and acoustic ceiling slabs, but have also found application as roof decking, and the latter application is especially wide-spread in England.

In Norway wood wool cement slabs for roofs are marketed under the designation t-roof deckings having a thickness of 150 mm, a width of 500 mm and lengths of'1990 mm and 2390 mm. The weight thereof is between 55 and 60 kg/m2.

In England corresponding slabs are marketed under various designations, and can have a variation of thickness from 50 mm to 125 mm, and without a reinforcement they will have lengths from 1800 mm to 3600 mm and widths of 500-600 mm.

2 Wood wool cement slabs are also used as acoustic, suspended ceilings, i.e. "freely" suspended panels which regulate the acoustic conditions in the room or hall in question, but such acoustic wood wool cement slab ceilings have hitherto not allowed the use of affixing thereto further decorative objects, for example lamps, etc., since the latters have to be affixed through said ceiling slabs to the ceiling structure itself, which means through the "acoustic ceiling".

The present invention has been developed in connection with such wood wool cement slabs generally, but is of special interest in connection with the renovation of existing roofs, especially in England. Here, there have previously been used roof structures onto which the wood wool cement is slabs have been mounted transversely on the roof joists, whereafter the roof covering itself was glued onto or adhered to the slabs themselves. However, between the roof slabs there will take place a movement which means that the gaps between the slabs may vary, for example in the range of 20 1 and 2 mm, which in turn involves that the on- glued roof covering is subjected to stretching and compressing forces and, consequently, will be weakened over time. Such a weakening will in time lead to cracks in the roof covering and the roof will thus not any longer be tight.

The repair of such untight roofs is effected by a patching gluing of the worst portions, but by renovation of the roof it is aimed to avoid this roof covering technique which involves the gluing of the roof covering to the wood wool 30 cement slabs.

Prior art

From Norwegian Building Research Institute's data sheet "Byiggforskserien" UDK 69.0224.3, A 525.206, spring 1985 "Compact roofs of wood wool cement slabs" it is suggested the covering of t-roof slabs with roofing paper which may be attached with warm asphalt or mechanical fastners. In con- i 3 nection with mechanical fastening it is suggested that firstly a layer of roofing paper having a polyester stem is rolled out and attached mechanically to the wood reinforcement, whereas across the overall roof there is fully adhered a top roofing paper with a moisture proof stem in warm asphalt.

However, this data sheet does not give any instructions for how a roof covering may be attached mechanically to the slabs themselves, which is necessary for allowing a effective and rational laying of the roof covering webs in running lengths.

Obiect of the invention is The object of the present invention is generally to provide an affixing technique which can be used in connection with especially wood wool cement slabs, and more specifically an affixing technique which can be used in connection with floating roofs which are to be laid out on a roof decking comprising roof slabs made of wood wool cement. The floating roof covering should then be able to distribute or absorb the movements of the subjacent wood wool cement slabs, and this floating roof covering itself could then in turn be covered by a further roof covering web, for example by means of a layer of asphalt. The lowest roof covering which is attached mechanically, will then be able to move sufficiently for being subjected to a minimum of unfavourable forces, whereas web number two may be fully welded on top of the subjacent foil, for example with overlapping.

The first roof covering should thus be allowed to be rolled out loosely and be mounted edge to edge and be attached mechanically to the slabs themselves.

The problem of achieving sufficient holding force in the wood wool cement slabs is due the fact that such wood wool cement slabs comprise flat wood wool fibres of approximate- 4 ly the same width (approximately 4,3 mm) and approximately the same thickness (0,6-1 mm), but with varying length and nesting degree. This will give relatively large cavities in the slabs, and these cavities may have uneven size and 5 location.

It is true that one can find certain types of wood wool cement slabs comprising some sort of reinforcement in the form wood poles embedded in the slab, but this form of rein- forcement would not be of interest for slabs having a thickness of 50 mm, but only for thicker slabs. However, even with such a reinforcement it would involve problems by using such rods for the affixing of a fastener means which should retain the above arranged roof covering in position, which is problem also exists in connection with the tracing of a subjacent structural beam.

What the present invention is aimed at is thus to provide a fixing technique in which the wood wool cement slab itself is to constitute the support for a fastener means, which especially is to be used for the mounting of mechanically attached roof coverings thereupon. One has previously been informed about fastener means which are especially applicable for the affixing in so-called "light weight brick works", the fastener means here comprising a closed plastic sleeve with an epoxy mixture, as well as a screw which upon the screwing in of the fastener means punctuates the sleeve and allows the epoxy mixture to expand in order to contribute to the attachment of the fastener means. This provides an improved hole fastening, but renders a relatively "small" possibility for expansion of the fastener means into the surrounding brick work.

There is also previously known an attempt to improve the holding ability of fastener means in wood wool cement slabs by means of tracks made therein, and wherein is provided a T-iron which is attached in the track by means of warm asphalt. However, this does not provide a good enough affix- i j ing of that portion of the T-iron which extends into the track, due to the varying viscosity of the asphalt in relation to temperature.

There has also been suggested throughgoing bolt means having a washer on the underside, but neihter such a technique has given any satisfactorily solution of the present problem.

Disclosure of the invention

The main object of the present invention is to provide a #espread cylinder" in the wood wool cement slab, which can resist large shear forces for thereby in its central portion to be able to affix a fastener means.

In other words, according to the present invention there is aimed for a medium which can be inserted into an appropriate recess in the wood wool cement slab, and which can penetrate into the pores of this slab not only by the original insertion of the medium itself, but also by the insertion of the fastener means which is to be affixed by said medium.

With this as a starting point a method of the type as mentioned in the preamble is characterized by the following steps:

a) to provide a non-throughgoing recess transversely to the main plane of the wood wool cement slabs, b) to introduce into said recess, possibly under pressure, an expandable, preferably bondable material for the filling/ expansion into said recess and into the slab cavities in the immediate proximity of said recess, c) to insert into said filled recess, by a not finished cured/expanded condition of said expandable material, a fastener means which by its insertion contributes to the filling up of the curing/expanding material in said slab cavities, d) and to let said fastener means be cured into said 6 expandable material for affixing a roof covering in relation to said wood wool cement slabs.

As expandable material there may be used an expandable adhesive, for example an expandable single-component material, preferably a onecomponent polyuretan. It is to be understood that two component materials can also be used, but it is preferred that the expandable component should withstand high temperatures, which can be the case if it is here the token about roof slabs which thereabove is provided with roofing webs arranged edge to edge and with a welding strip welded onto the roof web joints.

It is to be understood that this affixing technique can also be used for other purposes, for example in connection with ceiling slabs used as decorating elements or elements for regulating the acoustic effect in a building structure.

Correspondingly, the present invention is characterized by a device which in combination comprises:

a) an originally non-throughgoing recess provided transversely to the main plane of the wood wool cement slab, b) an expandable, preferably bondable material which has been cured in the recess and in the slab cavities in the immediate proximity of said recess, as well as c) a fastener means attached in the cured and expanded material.

Further features and advantages of the present invention will appear from the following description of embodiments, taken in connection with the appended drawings.

Brief disclosure of the drawings

Fig. 1 is a perspective view of a cut-out of a roof, which depickts how a roof covering is laid onto wood wool cement slabs in accordance with a known mounting technique.

1 7 Fig. 2 is a cut-out of a roof illustrating the mounting of a loosely rolled out roof covering which is mechanically attached to isolation slabs.

Fig. 3A and 3B illustrate sections through a portion of a wood wool cement slab prepared for and including a fastener means, as provided in accordance with the present invention.

Detailed description of embodiments

In Fig. 1 which illustrates a cut-out of a roof there is depicted how a roof comprising transversely arranged roof joists 1 and wood wool cement slabs 2 which are laid transversely of the joists 1, are covered with a web-shaped roof covering 3, the area of the longitudinally extending slab joints being covered by a narrow covering strip 4, and the end joints thereof being grouted with a filling mass 5. The slabs 2 are attached to the roof joists by means of fixings 6, for example nails or similar, and the roof covering 3 is attached to the upper side of the slabs 2 by means of an adhesive.

Along the peripheral edge of the house wall there is provided an L-shaped upstand 7, across which the edges 3a of the roof covering 3 have been passed.

Since the roof covering 3 is glued to the slabs 2 there will due to a relative movement between the roof slabs and roof covering exist a tearing accelerating transmission of force to the roof covering, which after some time will lead to the cracking of the roof covering, especially above the slab joints. Here, it will also be possible for the gluing to loosen and the roof covering or the foil 3 will depart from the roof decking slabs. one form of mending such a cracked and possible partly torn off roof, is to the fact of removing the loose parts followed by the gluing on of a new covering, which is not a good solution since the same relative forces then will give the same effect as before.

i 8 From Fig. 2 it appears how this problem can be solved by laying a socalled floating roof, this Figure illustrating a roof structure 10, which for example may comprise a wood roof, concrete, concrete elements, porous concrete elements or corrugated steal plates, whereas the panels or slabs 20 may constitute loosely mounted isolation slabs comprising mineral wool and/or expanded polystyrene.

In Fig. 2 there is further illustrated a loosely laid out roof covering 23 mounted end to end over said isolation slabs 20, and which in the area of the end to end edges are mechanically attached by means of a fitting 24, which in. turn is attached to the roof structure 10. Above the end to -is end joints there is welded a welding strip 25, and the mechanical attachment is such-that the finished mounted roof covering 23 can move in relation to the roof structure 10 and the loosely mounted isolation 20 to a sufficient degree for avoiding the development-of a tearing effect in the area of the slab joints.

On the top of this-floating roof there may additionally be _welded a further web-f if this should appear necessary, but the two webs will still-be mechanically attached to the roof structure, and therefore unnecessary tension which may develop in the area-of the slab joints will be avoided.

In Fig. 3A and 3B which illustrate an embodiment of the affixing device according to the present invention reference numeral 30 designates a cut-out of a wood wool cement slab, which usually comprises longitudinally extending flat fibres 31 of varying lengths, but with approximately same width and thickness. For example the thickness of the wood wool fibres may be approximately 0,6-1 mm, whereas the widths may be within the size range of 4-4,5 mm, whereas the length varies in the same manner as the degree of nesting. This means that between the fibres 31 there will exist relatively large cavities 32 of varying dimension and location.

1 i 9 However, in accordance with the present invention there is provided a recess 34 transversely to the main plane of the slab, the diameter of the recess being adapted to a possible fastener means, here a threaded bolt 33 which is to be affixed in the slab itself. Before the insertion of the bolt 33 there is, however, in the recess 34 introduced, possibly under pressure, an expandable, preferably bondable material 35a for filling/expanding in the recess 34, such that this expandable medium may spread out into the immediate proxi mity of the recess.

After an appropriate degree of filling of the expandable material in the recess 34, and prior to the final curing of the expandable material or the final expansion thereof, the bolt 33 is inserted into the curing mass, the bolt prefer ably being of such a shape that the screwing movement thereof will contribute to the filling in of the curing/ expanding material in the slab cavities 32a existing in the proximity of the recess 34.

After the bolt has been screwed into the recess 34, possibly with its tip end 33a extending through slab material itself, and the screw or the bolt has been subjected to an appropri ate turning moment, the fastener means will be cured into the expanded material which now has spread into the cavities around the recess 34 for thereby providing an anchoring zone which has penetrated well in between the relatively hori zontally extending wood fibres.

As expandable material there may preferably be used and expandable adhesive, for example an expandable singlecomponent polyurethane.

It is to be understood that also other expandable adhesives may be used, for example dual-component materials which are relative independent of temperature, but which may resist high temperatures in connection with the supply of a welding strip above the joints by means of a welding wagon.

In order to achieve a best possible attachment effect when laying a floating roof, attention must be paid to the quantity of expandable material which is to be introduced into the recess, as well as the manner in which the material is introduced.

The preparatory work for the laying of a floating roof will therefore be to the fact of drilling holes along the end to end edges of the webs which have been rolled out, and immediately after the introduction of the expandable medium in the recesses, the bolt should be inserted together with the associated fitting for attaching the roof covering web along the edge portions thereof. When inserting the bolt the expandable medium will be forced into the pores or cavities, and the medium will at the same time be subjected to expansion and curing. Appropriately, there may as a fastener bolt 33 be used a threaded bolt having a core diameter which is reduced towards the insertion end, and in the recess there may appropriately be introduced expandable material in a quantity corresponding to 2,5 times the volume of the recess.

Having a recess with a diameter of 8 mm in a slab of 50 mm, and a recess depth of approximately 40 mm there should be introduced a dosage quantity of approximately 6 cm3, i.e. corresponding to approximately 2,5 times the recess volume. The drilling diameter of 8 mm can then appropriately correspond to a mean stem diameter of the threaded portion of the bolt.

it may be appropriate if the bolt is inserted with a controlled movement for maintaining the structure of the wood wool cement slab itself, i.e. in such a manner that the fibres constituting the slab maintains their original position, namely substantially in a direction corresponding to the main plane extension, although mutually nested, for 1 1 1 j 11 thereby together with the expanding and curing material to provide a strengthened "reinforcement".

After the bolt 33 has been screwed into the curable material filling the recess there will in the area of this recess have developed an approximately cylindrically shaped cured zone having a larger diameter of approximately 70-80 mm at the centre portion, and having a somewhat reduced diameter towards the top and bottom, respectively.

The material of the fastener bolt 33 may for example be nylon, which renders a good adherence to for example the mentioned expandable singlecomponent polyuretan material.

Test results In a test performed by SINTEF there was used a fixing system comprising three parts, namely a "Rawlite" plastic screw having an outer diameter of 18 mm, an expandable bounding agent of the type "Borner-Pur", as well as a fitting of the type Isola-84.

In a 50 mm thick wood wool cement slab having a bottom layer including an asphalt base attached to the one side thereof there was drilled a hole of 8 mm diameter and of a depth of 40 mm through said layer and down into the slab. Thereafter the bonding agent "Borner- Pur" was introduces into the drilling hole by means of a hand driven pump. Thereafter the screw of type "Rawlite" was inserted into the drilling hole to a depth of 40 mm. The affixing system was thereafter allowed to cure for 18 hours at approximately +2.0C before testing.

Then the pull out strength was decided in accordance with certain standardized methods, the testing being divided in two experimental lines, namely a) statistic pull out strength for 10 fasteners under the use of constant machine speed of 5 mm/min, 12 b) pulsating applied load with step-wise increase by 1/5 of average capacity from static pull out, the 10 fasteners being tested with 200 cycles per load interval with deformation speed of 50 mm/min.

For the static pull out loads there appeared an average result for the failure capacity of 2975 N with a standard deviation of 367 N.

At pulsating pull out load there appeared a capacity at failure at 2450 N with a standard deviation of 403 N.

The capacity at failure was observed on the basis of either failure in the fastener, pull out from the base material, or a permanent deformation larger then 6 mm for the fastener itself or related to the pull out degree at the end of each load interval.

In accordance with NBI design sheet A544.206 the recommended design capacity can be computed using the formular: Xd 2 0f9 (Xm - k.s) where X. = average failure capacity s = standard deviation k = factor for number of samples.

If for example in Norway it is assumed a load factor of 1,6 taking into account the safety against wind damage, there may in accordance with NS 3479 be recommended a design capacity of the mentioned "Rawlite" fastener screw with "Borner- Pur" in wood wool cement slabs in accordance with: Xd = OP9 (2450 - 1,67 x 403) = 1599, which means.1600 N per fastener screw.

i i 13

Claims

P a t e n t c 1 a i m s

Method relating to the affixing to a support, especially the affixing of a roof covering (23) to a so-called wood wool cement slab (30) comprising substantially flat wood wool fibres in mixture with cured cement mortar, c h a r a c t e r i z e d by the following steps:

a) to provide a non-throughgoing recess (34) transversely to the main plane of the wood wool cement slabs (30), b) to introduce into said recess (34), possibly under pressure, an expandable, preferably bondable material (35) for the filling/expansion into said recess (34) and into the slab cavities (32) in the immediate proximity of said recess (34), c) to insert into said filled recess (34) by a not finished cured/expanded condition of said expandable material (35), a fastener means (33) which by its insertion contributes to the filling up of the curing/expanding material (35) in said slab cavities (32), d) and to let said fastener means (33) be cured into said expandable material (35) for affixing a roof covering (23) in relation to said wood wool cement slabs (30).
2. Method as claimed in claim 1, c h a r a c t e r i z e d i n that as expandable mate- rial (35) there is used an expandable adhesive, for example an expandable single-component polyuretan.
3. Method as claimed in claim 1 or 2, c h a r a c t e r i z e d i n that as fastener means (33) there is used a threaded bolt having a core diameter which is reduced towards the insertion end, and that in the recess there is introduced expandable material (35) in a quantity corresponding to approximately 2,5 times the recess volume.

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4. Method as claimed in claim 3, c h a r a c t e r i z e d i n that in the cavity comprising wood wool cement slab (30) there is provided a nonthroughgoing hole having a diameter corresponding to the 5 average diameter of the threaded bolt core, and that in the recess (34) there is filled approximately 6 cm3 expandable material (35).
5. Method as claimed in claim 3 or 4, c h a r a c t e r i z e d i n that the threaded bolt is controllably screwed into said recess (34) for the persever ance of the original fibre structure of said wood wool cement slab (30) with its fibres (31) running in planes substantially in parallel with the main plane of said wood wool cement slab (30), and for the provision of a reinforced cured material wherein said fibres (31) in the immediate proximity of said recess (34) constitute the reinforcement, said threaded bolt being received to the bottom of said recess (34) or possibly through the bottom of said recess (34).
6. Device for use in relation to affixing to a support, especially affixing a roof covering (23) to a so-called wood wool cement slab (30) comprising substantially flat wood 25 wool fibres in mixture with cured cement mortar, c h a r a c t e r i z e d i n that the device comprises in combination: a) an originally non-throughgoing recess (34) provided transversely to the main plane of said wood wool cement 30 slab (30), b) an expandable, preferably adhesive material (35) which has cured in the recess (34) and in the slab cavities (32) in the immediate proximity of said recess (34), as well as 35 C) a fastener means (33) affixed in the cured and expanded material (35).

1 i i
7. Device as claimed in claim 6, c h a r a c t e r i z e d i n that the expandable mate- rial (35) is for example an expandable adhesive, for example an expandable single-component polyuretan.
8. Device as claimed in claim 6 or 7, c h a r a c t e r i z e d i n thatthe fastener means (33) is a threaded bolt having a core diameter which is reduced towards the insertion end, and that the cured mate- rial constitutes an anchoring zone having a volume which originally corresponded to approximately 2,5 times the volume of the recess (34), but which in cured condition constitutes an anchoring zone having a larger diameter of approximately 7-8 cm.

is
9. Device as claimed in claim 8, c h a r a c t e r i z e d i n that the original recess (34) has a diameter corresponding to the average diameter of the threaded bolt core, and that the bolt is made from plastic.
10. Device as claimed in claim 8 or 9, c h a r a c t e r i z e d i n that the threaded bolt is screwed into the recess (34) under the perseverance of the original fibre structure of the wood wool cement slab (30), i.e. with the fibres (31) running substantially in planes which are parallel to the main plane of the wood wool cement slab (30), and that the substantially horizontally extending but mutually nested fibres 31 together with the cured mate- rial constitute a cured anchoring zone for said bolt, said fibres (31) in the immediate proximity of the re.cess (34) and the bolt constituting a reinforcement.

1
11. A method for affixing a roof covering to a support, substantially as hereinbefore described with reference to the accompanying drawings.
12. A device for fixing a roof covering to a support, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

1 1 i 1 1 Published 1991 atIbe Patent Office. State House. 66/71 High Holborn, LondonWCIR47P. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.