GB2172024A

GB2172024A - Fire-resistant building structure

Info

Publication number: GB2172024A
Application number: GB08505563A
Authority: GB
Inventors: John Griffiths Pilkington; Robert Dargo Gillon
Original assignee: Tac Construction Materials Ltd
Current assignee: Tac Construction Materials Ltd
Priority date: 1985-03-05
Filing date: 1985-03-05
Publication date: 1986-09-10
Also published as: GB8505563D0

Abstract

A structure is protected against fire by attaching to it a thermal insulation board to leave a cavity between structure and board, and providing in the cavity a heat barrier which consists of reflective flexible sheet material, such as aluminium foil, the material being positioned in the cavity so as to leave a gap on each side of the material. In a fire-protective construction, such as an internal wall or fire door, opposed thermal-insulation boards (2, 2a) include such a heat barrier (5), positioned as defined, in the cavity between them. Examples of board materials are given in the specification. <IMAGE>

Description

SPECIFICATION Fire-protective constructions This invention relates to fire-protective constructions.

When protecting structures against fire it is common to employ thermal insulation boards, that is to say boards of low organic matter content, of thermal conductivity less than about 0.5 wlm ec at ambient temperature, of density less than about 1500 kg/m3, and of modulus of rupture greater than about 0.5 N/mm2. Well known examples of such boards are those based on cementitious material, for example Portland cement or autoclaved calcium silicate, reinforced with fibres which may be asbestos but are now usually cellulose, synthetic organic fibres such as polyvinylalcohol or polyacrylonitrile fibres, or inorganic fibres such as glass or mineral wool fibres. Another example is the board consisting of exfoliated vermiculite cemented with sodium silicate, available under the trade mark VICUCLAD.Thermal insulation boards are available in a wide range of thicknesses, especially 3-80 mm; and the time for which a board will protect what lies behind it from a fire of given intensity will, or course, depend on the thickness of the board.

In one kind of fi re-protective construction at present in wide use to provide internal walls and fire doors, opposed thermal insulation boards have in the cavity between them an additional heat barrier of bulk mineral wool, glass fibres or the like. In another kind of construction, for example to protect external walls, a layer of mineral wool is fastened to the surface to be protected, and a single skin of boards is assembled by fixing the boards to spacers attached to the wall through the mineral wool layer, leaving a cavity between the mineral wool layer and the skin of boards. In a furthertype of construction, to protect structural steel columns, a single skin of boards is assembled to encase the column, leaving two cavities, one on each side of the upright of the column. In this case, no bulky heat barrier of mineral wool or the like is ordinarily used.

We have now found that a construction with a degree of fire protection adequate for many purposes, and not requiring a bulky heat barrier, can be obtained by providing, in the cavity or cavities already referred to, a heat barrier consisting of reflective flexible sheet material, for example metal foil, and particularly aluminium foil, the sheet material being positioned in the cavity so as to leave a gap on each side of the material. (The sheet material is thus not present as a facing on the thermal insulation board, by contrast with the aluminium facing present on plaster boards used in ceiling construction.) In those instances, as with protection of structural steel, where no bulky heat barrier was previously ordinarily used, the use of reflective flexible sheet material improves the degree of fire protection.

In its broadest aspect then, the invention provides a method of protecting a structure against fire which comprises (a) attaching to the structure a thermal insulation board to leave a cavity between structure and board, and (b) providing in the cavity a heat barrier which consists of reflective flexible sheet material, the material being positioned in the cavity so as to leave a gap on each side of the material. Of course, the order in which steps (a) and (b) are carried out is in principle a matter of indifference. Thus, one can proceed by first attaching the flexible sheet material to spacers secured to the structure, leaving a gap between the flexible sheet material and the structure to be protected, and then attaching the thermal insulation board to the spacers, leaving in turn a gap between the flexible sheet material and the insulation board.

According to another aspect, the invention provides a fire-protection construction comprising opposed thermal insulation boards having in the cavity between them a heat barrier consisting of reflective flexible sheet material, said sheet material being positioned in the cavity so as to leave a gap on each side of the material.

It is preferred that, viewed in transverse section, the sheet material should run diagonally of the cavity.

Preferably, the sheet material is attached to spacers, for example of timber or steel channel, between the opposed thermal insulation boards.

Examples of thermal insulation boards which may be used in putting the invention into practice are those sold under the following trade marks, which have the following characteristics (among others): Nominal Combustibility Density Fibre-re- to BS476 (kglm3) Binder inforcement Pt4 1970 TACFIRE 875 Portland Yes Non-combustible Cement TACBOARD 1200 " Yes SUPALUX 875 Autoclaved Ca Yes silicate VERMICULUX 450 " Yes MONOLUX 640 " Yes MASTERBOARD 875 " Yes Combustible MASTERCLAD 1200 " Yes Combustible VICUCLAD 430 Sodium silicate No Non-combustible ALPHIRE 380 Organic resin, Yes Combustible forming < 10% by weight of the board The invention will now be further described with reference to the accompanying drawings, in which: Figure lisa horizontal section of one form of an internal wall; Figure 2 is a horizontal section of a second form of internal wall; Figure 3 is a horizontal section of a third form of internal wall; and Figure 4 is a horizontal section of a fourth form of internal wall.

In each Figure, the internal wall 1 comprises opposed thermal insulation boards 2, 2a (TACBOARD; 12 mm thick) spaced apart by spacers 3 (at 600 mm intervals along the wall), which in Figures 1 to 3 are of timber and in Figure 4 are of steel. In the cavity 4 (width 70 mm) between opposed boards 2, 2a there is a sheet 5 of aluminium foil (BACOFOIL of British Alcan Aluminium Ltd; 0.01 mm thick) formed from vertically overlapping 600 mm widths (overlap 50 mm) of the foil. The sheet divides each cavity into two, so that gaps 6, 6a are left between the foil and each opposed board 2, 2a. The foil may be secured to the spacers by manual crimping during assembly. Attachment means to secure the boards to the spacers should be such as to avoid corrosion of the aluminium foil, whether by exposure to alkali released from the board or bythe setting up of an aluminium/other metal couple at the junction of fastener and foil.

In the construction shown in Figure 2, a strip of aluminium foil 11 is interposed between each spacer and thermal insulation board 2 so as to give equivalent fire performance on each side of the construction.

A construction made as in Figure 4 gave, in a small scale fire test carried out generally in accordance with BS 476 Pt 8 1972, a fire resistance period of 1 hour 45 minutes. Without the aluminium foil, a period of only 55 minutes was achieved.

Claims

1. A method of protecting a structure against fire which comprises (a) attaching to the structure a thermal insulation board to leave a cavity between structure and board, and (b) providing in the cavity a heat barrier which consists of reflective flexible sheet material, the material being positioned in the cavity so as to leave a gap on each side of the material.

2. Fire-protective construction comprising opposed thermal insulation boards having in the cavity between them a heat barrier consisting of reflective flexible sheet material, said sheet material being positioned in the cavity so as to leave a gap on each side of the material.

3. Fire-protective construction according to Claim 2, in which, viewed in transverse section, the sheet material runs diagonally of the cavity.

4. Fire-protective construction according to Claim 2 or 3, in which the sheet material is attached to spacers between the opposed boards.

5. Fire-protective construction according to any of Claims 2 to 4, in which the reflective flexible sheet material is metal foil.

6. Fire-protective construction according to Claim Sin which the metal foil is aluminium foil.

7. Fire-protective construction according to any of Claims 2 to 6, in which the thermal insulation boards employed are non-combustible according to BS 476 Pt 4.

8. Fire-protective construction according to any of Claims 2 to 6, in which the thermal insulation boards are fibre inforced cementitious boards.

9. Fire-protective construction according to Claim 8, in which the cementitious binder of the board is Portland cement.

10. Fire-protective construction according to Claim Bin which the cementitious binder of the board is calcium silicate.

11. Fire-protective construction according to any preceding claim, in which the board is of density at least 350 kg/m3.