GB2303788A

GB2303788A - Porous, breathable fire barrier, the pores closing on heating.

Info

Publication number: GB2303788A
Application number: GB9609645A
Authority: GB
Inventors: Derek Ward
Original assignee: Environmental Seals Ltd
Current assignee: Environmental Seals Ltd
Priority date: 1995-07-29
Filing date: 1996-05-09
Publication date: 1997-03-05
Anticipated expiration: 2016-05-09
Also published as: GB9515588D0; GB9609645D0; GB2303788B

Abstract

A fire barrier for use with thatched roofing comprises an open weave sheet woven from glass fibres or a metallic mesh or perforated metal sheet coated with a fluid in which is mixed a quantity or between 5% and 20% by weight of intumescent material. The intumescent is preferably in particulate, e. g. powder, form. A preferred quantity of intumescent material is between 8% and 2% by weight, typically 10% by weight and may be exfoliating graphite or an alkaline metal silicate. Also disclosed is that these sheets may be layered into the thatch.

Description

FIRE BARRIER FOR THATCHED ROOFING This invention relates to fire barriers for thatched roofing and to thatched roofing including such barriers.

Fire barriers are known which are either coated with or include intumescent materials which expand rapidly in the presence of fire to seal off protected areas and to prevent a fire hazard passing from one area to another.

In some cases, there is a requirement for a fire barrier to allow air to flow from one side of the barrier to the other. Such need arises, for example, in thatched roofs of buildings in which a continuous fiow of air through the sheaths of straw thatching is essential.

The present invention sets out to provide such a fire barrier.

Thatched roofing is, of course, readily combustible and is particularly vulnerable to chimney embers, fireworks and indeed all manner of fire hazards. Fire rr^^fcd sheets which are intended to overlie a thatched roof are unsightly and detract from the aesthetic qualities of a properly thatched building. Fire barriers in accordance with the present invention are permeable until subjected to fire and are intended to lie below the upper layer of thatching thereby not detracting in any way from the appearance of the thatching. In the event of a fire, it is only the exposed thatch layer which is destroyed, thereby reducing significantly the cost of renovation.

According to the present invention in one aspect there is provided a fire barrier for use with thatched roofing which comprises a permeable sheet and coated with a fluid in which is mixed a quantity of between 5% and 20% by weight of intumescent material, the permeability of the sheet being such that the pores of the sheet remain open until the barrier is subjected to heat sufficient to cause the material to intumesce.

The intumescent is preferably in particulate, e.g. powder, form.

A preferred quantity of intumescent material is between 8% and 12% by weight, typically 10% by weight.

In another aspect, there is provided roof coverings which comprise a plurality of layers of thatching separated by a sheet or sheets of a permeable material which extends or extend over the entire length and width of the overlaid thatching layers and which is or are coated with a fluid in which is mixed a quantity of between 8X and 12% by weight of intumescent material, the or each sheet retaining its permeability after coating.

The sheet may comprise an open weave sheet woven from glass fibres. Alternatively, the sheet may comprise a metallic mesh or perforated metallic sheet.

The fluid may take the form of a water or oil based paint or varnish and the granulated intumescent material may comprise powdered exfoliating graphite and/or an alkaline metal silicate such as sodium silicate.

One or both sides of the sheet may be coated. If both sides are coated, one coating may act as an adhesive for securing the sheet to a surface to be protected. Alternatively an adhesive may be provided for this purpose. The adhesive may be mixed with a quantity of particulate intumescellt material, this quantity being typically between 5% and 20% by weight. The intumescent material may comprise powdered exfoliating graphite and/or an alkaline metal silicate such as sodium silicate.

By "open weave" is meant a woven sheet in which discrete openings are provided between neighbouring fibres. The discrete openings are typically from 1 to 3 mm in width. For metallic meshes or perforated sheets, the mesh openings or perforations are again typically from 1 to 3 mm in width or diameter.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which Figures 1 and 2 are plan and sectional views of a fire barrier in accordance with the invention.

As will be seen from Figure 1 of the drawings, the fire barrier comprise an open weave sheet 1 woven from glass fibres in which the individual fibres essentially define an irregular mesh which is coated with a fluid mixed with a quantity of powdered exfoliating graphite and/or sodium silicate. The coating is indicated by reference numeral 2. The openings of the woven sheet defined between neighbouring glass fibres remain open after coating. The fluid may comprise a water or oil based paint mixed with a required quantity of powdered exfoliating graphite and/or sodium silicate to define a substantially homogenous mix.

Typically, the amount of powdered intumescent represents 10% by weight of the mix. A range of quantities of powdered intumescentis from 5% to 20% by weight. A preferred range of powdered intumescent is between 8% and 12% by weight.

As will be seen more clearly from Figure 2, the fluid is coated onto the surface of the woven sheet 1 with a layer of adhesive 3 provided on the undersurface of the sheet. The adhesive may also be mixed with aquantity of intumescent material, e.g. powdered exfoliating graphite and/or sodium silicate. This quantity is typically of 10% by weight.

In a unillustrated embodiment, the fibrous sheet is replaced by a metallic mesh or perforated sheet.

As mentioned previously, thatched cottages are vulnerable to being set on fire by for example embers leaving a chimney, fireworks or other hazards. Once a fire starts then normally the entire thatching of the cottage is destroyed.

As also mentioned previously, it is a requirement of thatch roofing that it can breath. When using a fire barrier in accordance with the invention, the permeable barrier is sited immediately below the upper layer of straw thatching and in the event of fire will immediately intumesce to provide secure protection to the majority of the thatching which lies below the barrier. In this event only the surface layer of thatching need be replaced.

With the fire barrier in place therefore the appearance of the thatching is unchanged. Also the barrier enables the thatching to breath in a required manner and as mentioned above in the event of fire provides secure protection for all but the surface layer of thatch.

It will be appreciated that the foregoiny is merely exemplary of fire barriers in accordance with the invention and that various modifications can readily be made thereto without departing from the true scope of the invention

Claims

CLAIMS 1. A fire barrier for use with thatched roofing which comprises a permeable sheet and coated with a fluid in which is mixed a quantity of between 5% and 20% by weight of intumescent material, the permeability of the sheet being such that the pores of the sheet remain open until the barrier is subjected to heat sufficient to cause the material to intumesce.
2. A fire barrier as claimed in Claim 1 wherein the sheet comprises an open weave sheet woven from glass fibres.
3. A fire barrier as claimed in Claim 1 wherein the sheet comprises a metallic mesh.
4. A fire barrier as claimed in Claim 1 wherein the sheet comprises a perforated metallic sheet.
5. A fire barrier as claimed in any one of the preceding Claims wherein the quantity of intumescent material is between 8% and 12% by weight.
6. A fire barrier as claimed in any one of the preceding Claims wherein the fluid is a water or oil based paint or varnish.
7. A fire barrier as claimed in any one of the preceding Claims wherein the particulate intumescent material comprises powdered exfoliating graphite.
8. A fire barrier as claimed in any one of the preceding Claims wherein the particulate intumescent material comprises an alkaline metal silicate.
9. A fire barrier as claimed in any one of the preceding Claims wherein one side of the open weave sheet is coated with an adhesive.
10. A fire barrier as claimed in Claim 3 wherein the adhesive is mixed with a quantity of particulate intumescent material.
11. A fire barrier as claimed in Claim 10 wherein the quantity of intumescent material is between 5% and 20% by weight.
12. Roof coverings which comprise a plurality of layers of thatching separated by a sheet or sheets of a permeable material which extends or extend over the entire length and width of the overlaid thatching layers and which is or are coated with a fluid in which is mixed a quantity of between 8% and 12% by weight of intumescent material, the or each sheet retaining its permeability after coating.
13. A fire barrier as described herein and as described with reference to Figures 1 and 2 of the accompanying diagrammatic drawings.