Presently a fire in one building of a terrace quickly spreads to the adjoining buildings particularly through the neighbouring roof spaces. The present invention sets out to provide a fire-resistant spacer which operates to prevent the spread of fire between adjoining buildings or building sections for an enhanced period of time, especially a period in excess of one hour.

According to the present invention in one aspect, there is provided a fire-resistant spacer for separating tiled or slatted roof structures of adjoining buildings or building sections, the spacer comprising at least one sheet of intumescent material and at least one sheet of deformable material sealed within an envelope of flexible material, and a rib of flexible cellular fire-retardant foam or sponge in contact with an exposed surface of the envelope between opposed side edges thereof, the arrangement being such that in use the sides of the sealed envelope in which the intumescent material is present extend to positions at which they can be secured to neighbouring roof structure (preferably joists) of adjoining buildings or building sections with the rib extending between these neighbouring structures and to a height at least equal to the height of neighbouring tile battens of the roof structures, the sealed envelope and rib being subsequently covered by roof tiles.

The sheet of intumescent material may include or be coated with a mixture of particulate ceramic material, an intumescent substance and a binder. The intumescent material may comprise exfoliating graphite and/or sodium silicate in granular and/or powder form. The sheet containing the intumescent material may comprise a non-woven mat or sheet. The initial thickness of the sheet is preferably from 2 to 3mm and the sheet thickness when intumesced preferably exceeds 25mm.

The deformable sheet may comprise a wire mesh and the material of the envelope may comprise metallic foil or like material, reinforced foil paper, craft paper, or a plastics sleeve.

The rib of flexible cellular fire-retardant foam or sponge may be secured to a surface of the envelope and may be coated on at least one of its surfaces with a primer solution including a sealant and a flowable coating of a fire-retardant material. In this embodiment, the primer solution operates to close the open pores of the coated surface of the rib and provides a bond to which the fire-retardant coating can adhere. The primer solution may comprise an aqueous solution of an acrylic copolymer, including ammonium polyphosphate. The fire-retardant coating may comprise a chlorinated vinyl copolymer system which includes a quantity of ammonium polyphosphate, zinc borate, or magnesium and calcium carbonates. The foam or sponge may comprise polyurethane or a silicone coated with a silane primer.

In another aspect, there is provided a felted, tiled or slatted roof structure comprising a plurality of spaced joists and tile or slat supporting battens, and a fire- resistant spacer positioned between one or more neighbouring pairs of joists, the spacer comprising at least one sheet of intumescent material and at least one sheet of deformable material sealed within an envelope of flexible material, and a rib of flexible cellular fire- retardant foam or sponge in contact with or secured to an exposed surface of the envelope between opposed side edges thereof, the envelope side edges being secured to each of the neighbouring joists and the height of the rib, before assembly, being greater than the height of neighbouring tile or slat battens whereby, in use, the ribs are urged into contact with the felted roof surface by the tiles or slats.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which:- Figure 1 is an isometric view of a fire-retardant spacer in accordance with the invention; Figure 2 is a cross-section taken along line II-II of the fire-retardant spacer illustrated in Figure 1; Figures 3 and 4 are end views of spacers in accordance with the invention positioned below tiles of a roofing structure; and Figure 5 shows the illustrated spacer assembled between adjoining roof structures of neighbouring buildings.

The fire-retardant spacer illustrated in the drawings comprises a sheet of intumescent containing or coated material 1 and a sheet of deformable wire mesh 2 located within a sealed envelope 3 of metallic foil. The intumescent sheet may comprise a sheet marketed by the Applicants under their registered trade mark Multigraf. Alternatively, it may comprise other similar intumescent containing or coated sheet products marketed by Applicants or others.

The thickness of the intumescent sheet used is preferably of the order of 2 to 3mm; when intumesced in the event of fire the thickness preferably increases to a minimum of 25mm. The wire mesh is typically produced from aluminium or steel with generally square or round openings of between 10 and 50mm. The envelope 3 may comprise reinforced foil paper; alternatively, the envelope may comprise a folded foiled sheet, a plastics sleeve or folded and sealed craft paper.

Adhered to one surface of the foil envelope is an elongate rib 4 of flexible cellular fire-retardant foam or sponge. In a preferred embodiment, the rib 4 comprises a length of impregnated fireproof sponge. Alternatively, it may comprise rockwall, glasswall, a ceramic material or a mixture of two or more of these substances. The rib 4 extends between opposed upper and lower edges of the sealed envelope and is positioned generally centrally between the envelope side edges. The height of the rib is at least equal to the height of conventional roof battens 5 to which roofing tiles 6 are secured. Preferably the height of the enveloped rib exceeds the height of the battens by a small amount whereby the rib is compressed by the overlying tile to eliminate any voids which may otherwise be present.

The illustrated sheet of intumescent material may comprise ceramic or like fibres mixed with exfoliating graphite and/or sodium silicate in granular, powder or chip form.

Other intumescent compositions may be employed. The wire mesh is provided to enable the envelope to be shaped on site to conform to any particular required configuration.

The rib of polyurethane foam material is, in one embodiment, impregnated with an aqueous solution of a fire retardant material and is coated on some or all of its surfaces with a solution of a acrylic copolymer system which includes ammonium polyphosphate.

At temperatures in excess of 250°C to 300°C the ammonium polyphosphate forms phosphoric acid which reacts with the fire-retardant coating of the rib. This primer coating has a viscosity similar to that of water and acts to seal the open cells of the polyurethane foam. The primer coating therefore seals the exposed surfaces of the polyurethane rib whilst retaining its flexibility characteristics. The primer coating also provides a bond to which the subsequently applied fire-retardant coating can adhere.

Referring now to Figures 3 and 4, it will be seen that the outwardly extending sides 5 of the spacer are positioned below the opposed ends of neighbouring battens 6 and spaced from the undersurfaces of these battens by conventional roofing felt 7. Tiles 8 are positioned over and above the spacers and, in the positions shown in Figure 4, compress the spacer to remove any voids which might otherwise be present.

As will be seen from Figure 5, in use the spacer is secured along the edges of its sides 5 to adjacent joists of adjoining roof structures with the rib 4 positioned between the joists and below the sealed envelope. The height of the rib either equals or exceeds the height of the neighbouring battens to which the roof tiles are secured. Once in position the upper surface of the envelope is covered by roofing tiles in the normal way, the pressure of these urging the rib and the fire-retardant spacer into contact with the roofing felt which overlies the adjoining structures.

The enveloped spacers extend up to or overlie the ridge of the roof structure and are covered and compressed by ridge tiles 9.

In the event of fire the spacers intumesce to create an effective barrier to prevent the passage of fire from one roof structure section to an adjoining roof structure section.

It will be appreciated that the foregoing is merely exemplary of fire-resistant spacers in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention.