GB2164970A - A roof covering - Google Patents

Abstract

A roof covering is formed by a heat insulating layer of expanded plastics foam boards 4A, 4B the joints between them being covered by an adhesive strip 5 having a release agent on its upper surface. A membrane 6 formed by a mixture of bitumen and a contact adhesive is applied over the boards 4 and strip 5 to provide water proofing. If the boards 4 separate due to shrinkage the release agent on the strip 5 allows the membrane 6 to stretch without breaking. <IMAGE>

Description

SPECIFICATION A roof covering This invention relates to a roof covering of the type comprising a heat insulating layerformed by boards of expanded synthetic plastics material placed edge to edge and covered by a waterproof layer of a bitumen based material. The boards are preferably formed by extrusion to give them smooth upperand lower surfaces.

This type of structure has proved very popular in the pastwhen, to install it, hot bitumen is applied to a roof deck, of concrete, metal, plywood etc., and allowed to cool to about 85"C when it becomes tacky. The polystyrene boards are pressed onto the bitumen so as to hold them in position. Athin glass tissue base felt carrying a soft form of bitu men on its underside is then laid loosely overthe polystyrene and hot bitumen is used to bond at least a second layer of felt over that, causing the soft bitumen on the basefelttofurther soften andsticktothe polystyrene. The second and subsequent layers of roofing felt are madeto B. S. 747.

Roofing installed in this way has not withstood the test of time and it has been found that the multi layer waterproofing comprised of roofing felt splits, blisters and subsides. It is the inventor's beliefthatthese widespread problems arise from damage caused to the polystyrene during application ofthe hot bitumen applied at 150"C-220"C and, in many instances from progessive solar induced heat-shrinking ofthe polys tyrenecausingtheboardsto partand causing the roofing felt to slit along lines adjacent to where the polystyrene boards abut each other.It will be understood that polystyrene has a heat distortion capability at about 74 C and starts to melt and disintegrate at approximately 80"C, from which it can be seen that to put such a substance into intimate contact aith hot bitumen will be bound to cause damage. It is believed that given a dark surface finish the solar gain temperature atthe insulanttop surface can attain a temperature of 80"C i.e. in excess of 74"C.

This invention provides a roof covering ofthe type referred to in which the bitumen based material is a mixture having a plastic consistency and adhesive properties allowing itto be made to adhere to the expanded plastics material by the application of pressure. Because of its plastic consistency it can stretch so asto accommodate shrinkage of the underlying heat insulating boards and because of its contact adhesive properties it can be applied directly onto the heat insulating boards without use of heat or solvents which would damage them. The cohesive strength of bond requires to be adequate to retain in position the roofing system at its various interfaces against wind suction.

Suitable bitumen based materials are readily available e.g. from HEY'DI (G.B.) Ltd. of No.3 Eastern Industrial Estate, Newcraighall Road, Edinburgh underthetrade name HEY'DI SK2000, HEY'DI SK2000 Sand HEY'DI SK 2000ALU, the formertwo having a polythene carrier sheet which supports the bituminous substance and the latter having an aluminium carrier sheet which can be an advantage since it serves to reflect solar energy, thereby reducing heat shrink age to a minimum, and provides fire reistance. Such materials are supplied with a silicone treated release sheet on the side opposite the carrier sheet and it is necessary to remove this.Thus the invention also provides a method of surfacing a roof comprising: applying boards of expanded plastics material to the roof and then applying a sheet of a contact adhesive bituminous based material over the expanded plastics material after removing a release sheetfrom a surface ofthe self adhesive material.

The bituminous mixture is preferably a mixture containing bitumen and a natural or synthetic rubber.

The natural or synthetic rubber can be replaced by other substances known for their contact adhesive properties. A suitable non-aggressive solvent could also be included in an adhesive.

The invention has a second aspect in accordance with which there is provided a roof covering comprising thermal insulating boards placed edge to edge and made of a material which is subjectto shrinkage and a waterproof layer bonded to the sheets and extending across adjoining edges of the boards, characterised by anti-adhesion means inhibiting adhesion between the waterproof layer and border portions ofthe insulating boards bordering the edges thereof.

By employing an "anti-adhesion means" in this way any stretching ofthe waterproof layer due to shrinkage ofthe insulating boards is distributed over a substantial area ofthe waterproof layer. Splitting of the latter is thus made much less likely. The "antiadhesion means" can readily be provided by adhesive tape having one adhesive side attached to the insulating boards and an opposite side carrying a silicone or other release agent.

One way in which the invention may be performed will now be described with reference to the accompanying drawings in which Fig. 1 illustrates a schematic vertical cross-section through partofa roof covering constructed in accordance with the invention; and Fig. 2 illustrates a cross-section similarto that of Fig.

1 but illustrating the effect of exposure of the roof covering to solar heat over a period of time.

The roof covering shown in Fig. 1 is applied to a concrete roof deck 1 as follows.

First a primer 2 is preferably applied to the concrete.

This can be any one of many suitable products. HEY'DI SK primer is considered particularly suitable and is available from the aforementioned supplier.

Next a cold adhesive 3 isapplied, this preferably also being a bitumen, synthetic rubber, solvent base productsuch as is available, again fromforexample HEY'DI (G.B.) Ltd.. Their K100 Cold Adhesive, which of thixotropic character is considered particularly suitable since it is not agressive to polystyrene.

Boards, such as shown at 4A and 4B of rigid closed cell expanded and and extruded polystyrene foam having smooth continuous sealed upper and lower surfacesarethen applied, with their edgesabutting each other, to form a heat insulating layer. A suitable materialforthe boards 4is available underthetrade name ROOF MATE from The Dow Chemical Company.

A high density expanded bead polystyrene could be used as a second best alternative to extruded foam.

This could either be moulded or cut from slab stock, through the latter possibility is not preferred since it tends to produce a dusty friable surface less likely to adhere to a self adhesive membrane 6 nowto be described.

Athin paper strip 5 of width about 50 mms to 150 mms (preferably about75 mms) having a self adhesive layer on one side and a siliconised non-stick layer on the otherside is then applied, with its adhesive side down, over the joints between the insulating boards. A suitable adhesive strip is available from Samuel Jones & o., St. Neots, Cambridge underthetrade name TAKSTRIP.

Having applied the strip 5, a preformed roll of HEY'DI SK2000, HEY'DI SK2000S orHEY'DI SK2000 ALU is unrolled and itssiliconised release sheet removed to reveal the adhesive membrane 6. This is pressed onto the surfaces ofthe boards 4 and over the joints covered by the strip 5. The protective polythene or aluminium carriersheet 7forthe self adhesive membrane6formsthetopsurfaceofthe roof covering.

Since the membrane 6 adheres by its own contact adhesive propertiestothe insulating boards4no damage occurs to the latter as was the case with a hot application of bitumen applied atatemperatureof between 1 50 C and 220"C orthereabouts and thus the problems of localised disintegration ofthe polystyrene and subsequent blistering ofthe weatherproofing can be expected at least to be greatly reduced, and possibly totally eliminated.The use of a flexible cold adhesive belowthe insulating boards and the underlying surface such as can occurwhen similar boards are set in partially cooled bitumen as previously described.The shrinkage ofthe boards 4 is also tolerated by this construction as is illustrated in Fig. 2.

Referring to Fig. 2 itwill be seen thatthe boards 4A and 4B have diminished in size, more attheirupper surfaces than at their lower surfaces since the former are more exposed to radiation from the sun. Substantially less shrinkage normallytakes place atthe lower portion.

The shrinkage has caused the paper stripS to split into parts 5A and 5B in the illustrated case, though in a less severe example ofshinkage the strip may stretch.

In either event the silicone release agent on the upper surface of the strip means all ofthe membrane 6 above thestripstretches in orderto provide the necessary waterproof bridge between the uppersurfaces of boards 4A and 4B or is not stretched at all. The degree of extension per unit length is significantly less than if the strip 5 were not included. Nevertheless a construc tion without such a strip may accommodate sufficient shrinkagesince the membrane 6 is of plastic con sistencyso that its upper part can, being supported by the sheet7, retain its original form whilstalowing the lower part to flow to the left and right with movement ofthe boards 4.

In the condition shown in Fig. 2 it isto be noted that the upper carriersheet7 is held undertension so as to prevent collapse ofthe waterproof bridge between the boards 4A and 4B. The consistency ofthe membrane 6 is such that it is not selfsupporting and cannot retain a condition oftension on itsown.Thus itwould collapse if notforthe presence of the carrier sheet 7.

It is believed that the illustrated technique will solve the problems previously described and create a renewal ofthe practice of using roof coverings incorporating an extruded polystyrene or moulded polystyrene board. Not only can the aforementioned specific problems be overcome, but the construction as described is particularly resistantto splitting and mechanical damage, the membrane 6 having self healing properties; and it is furthermore particularly easy to repair,this being possible using a "patch" of the same material as the preformed roll.

Claims (6)

1. A roof covering comprising a heat insulating layerformed by boards of expanded plastics material placed edge to edge and covered by a waterproof layer of a bitumen based material characterised in that the bitumen based material is a mixture having a plastic consistency and adhesive properties allowing itto be madetoadheretotheexpanded plasticsbythe application of pressure.

2. A roof covering according to Claim 1 including a sheet of metal foil or plastics material on top ofthe waterproof layer.

3. A roof covering comprising heat insulating boards placed edge to edge and made of a material which is subject to shrinkage and a waterproof layer bonded to the sheets and extending across adjoining edges ofthe sheets, characterised by anti-adhesion means inhibiting adhesion between the waterproof layer and border portions ofthe insulating sheets bordering the edges thereof.

4. A roof covering according to Claim 3 in which the anti-adhesion means is adhesive tape having one adhesive side which is adhered to the insulating sheets and one side carrying a release agent.

5. A roof covering substantially as described with reference to Fig. 1 ofthe accompanying drawings and substantially as illustrated therein.

6. A method according to Claim 4 or 5 in which the carrier sheet is metal foil or synthetic plastics material.

6. A method of surfacing a roof comprising: applying sheets of expanded plastics material to the roof and then applying, over the expanded plastics material, a sheet of self adhesive bituminous based material carried by a carrier sheet.

7. A method ofsurfacing a roofsubstantially as described with referenceto Fig. 1 ofthe accompanying drawings.

Amendment to the claims have been filed, and have the following effect: Claims 1 to 6 above have deleted ortextually amended.

New or textually a mended claims have been filed as follows: CLAIMS

1. A roof covering comprising a heat insulating layerformed by boards of expanded plastics material placed edge to edge, the covering being made waterproof by a layer of a bitumen based mixture having a plastic consistency and adhesive properties allowing itto be made to adhere to the expanded plastics material by the application of pressure.

2. Aroofcovering according to Claim 1 includinga sheet of metal foil or synthetic plastics material on top ofthe waterproof layer and forming the top surfaceof the roof.

3. A roof covering substantially as described with reference to Fig.1 1 of the accompanying drawings and substantially as illustrated therein.

4. Amethodofsurfacinga roof comprising: applying sheets of expanded plastics material to the roof and then making the surfacing waterproof by applying, overthe expanded plastics material, a sheet of self adhesive bituminous based material carried by a carrier sheet.

5. A method according to Claim 4 in which the carrier sheetforms the top surface of the roof.