FIRE STOPS FOR USE IN BUILDINGS

Abstract: An element (1) for use as a fire stop for installation in cavities in buildings consists of an elongate generally rectangular cylindrical element (2) formed of a single ply mat of mineral fibre wool having a density of more than 60 kg/m<3>, with air impermeable fire resistant foil (3, 4) bonded to and substantially covering the surface of two opposite longitudinal faces. The density of the mineral wool core (2) and the bonded foils (3, 4) provide the fire stop (1) with adequate resistance to self-deflection and resilience in the plane of the coils (3, 4). The element (1) is fitted into a cavity with the foils (3, 4) extending across the cavity, preferably with the mineral wool core (2) under compression.

Description: FIRE STOPS FOR USE IN BUILDINGS This invention relates to fire stops for installation in cavities in buildings, for instance between an access floor and a wall, or between two leaves of a cavity wall. It is known to use cavity fire stops consisting of strips or elongate element of mineral wool to form fire stops in cavities within buildings. Such cavities may be between the cladding or curtain walling and a structural element, such as a concrete floor slab, to be fire stopped. The fire stops can be used in both vertical and horizontal plains. The strips of mineral fibre material are generally fitted with a slight compression in the direction perpendicular to the leaves of the cavity being stopped. In a vertical cavity, the strips are usually held in place by the use of brackets protruding horizontally from the first leaf to be constructed. Where the cavity to be fire stopped is longer than the length of slab as supplied, two slabs are used end to end, generally with fire stopping performance being improved by the use of stepped or rebated ends which interlock with one another. The mineral wool elements may have integral foil smoke barrier facings, used in an orientation such that the foil barrier lies perpendicular to the sides of the cavity being fire stopped. One product which is commercially available under the trade name Lamatherm and described in GB-A-2262228 is supplied as a rectangular precursor slab which is formed from mineral fibre lamellae oriented so as to provide suitable bending resistance to the fire stop product. The rectangular slab is cut on site to elements of the desired width, depending on the depth of cavity to be closed, and fixed in position using the usual brackets. The rectangular slab is provided with a foil barrier and the cut elongate elements are oriented in the cavity with the foil perpendicular to the leaves. Whilst this product has good flexibility, to provide resilient fixing under compression within the cavity, the production process for such slabs, requiring the cutting and orientation and adhesion of lamellae, is complex and expensive. The present invention seeks to provide a product having performance as good as the Lamatherm product described above, including the desired resilience to compression with longitudinal stiffness, but using more simple production techniques. Many processes are known in which, during the production of mineral fibre web, a loosely compacted mineral fibre web is subjected to longitudinal and, optionally, height compression. For instance such processes are described in CH-A-679161, EP-A-0560878 , WO-A-95/20708, WO-A-94/16162 , WO-A-88/00265 , US-A-2409066 , WO-A-95/20707 and CH-A-620861. A feature of the products produced by the prior art processes is that the web produced tends to have inadequate bending resistance, especially for webs having a final density of lower than 100 kg/m 3 . WO-A-88/00265 and WO-A-92/13150 , each describe a process in which length compressed mineral fibre web is split into two continuous strips, height compressing one of the strips and feeding it back on to the other web. In WO-A-95/20707, an insulating mat formed of mineral fibre for instance made using a process involving longitudinal compression, for use as an insulation panel, has an air permeable covering over one or both of the two main surfaces of the web. The air permeable covering is, for instance, formed of perforated foils, including a layer of metal foil. The air permeability of the foil is measured in air resistant units, and the air resistance is less than 100 mm water column. The density of the mineral fibre web is in the range 15 to 60 kg/m 3 , where the mineral fibre is rockwool . A new product according to the invention comprises an elongate rectangular cylindrical element having a rectangular cylindrical mineral fibre core and an air impermeable fire-resistant foil bonded to and substantially covering the surface of two opposite longitudinal faces, characterised in that the core is formed of a single ply mat and has a density of more than 60 kg/m 3 . The mineral fibre core of the element of the invention is preferably made by a process in which the web is subjected to length compression during production. This length compression is preferably such as to orient fibres predominantly in a plane substantially perpendicular to the machine direction and to the cross direction of the line on which the web is produced. This has the effect of making the wool resilient to compressive forces applied parallel to the machine direction. Preferably the foil is applied to the web, and adhered using a suitable adhesive, after to curing of resin impregnated in the length compressed wool in an oven, by application to the two faces of the cured web in line. The elongate element is preferably cut so that its longitudinal axis lies perpendicular to the machine direction. Consequently in the product of the invention, the fibres of the core are oriented predominantly in a plane substantially perpendicular to the surfaces to which the foil is bonded. The length compression step has conferred resilience upon application of a compressive force between the two longitudinal faces to which foil is not bonded. This results in a tight fit upon being compressed in a building cavity. In the invention the impermeable fire-resistant foil preferably comprises a continuous non-perforated sheet of metal, preferably of aluminium. A suitable thickness for the aluminium sheet is 20 μm. It may be a laminate of aluminium with a reinforcing layer, for instance formed of fibre glass scrim e.g. 80-120g/m 2 weight and a continuous or discontinuous surface lamina of a thermoplastic material to act as adhesive. Where the adhesive is a thermoplastic material, the foil can be adhered to the mineral wool web by heating the adhesive to a temperature above the melting temperature, contacting it with the web and allowing the adhesive to cool and solidify, for instance by the use of heated rollers to apply simultaneous heat and pressure. The element of the invention is preferably retained in the cavity required to be fire stopped under compression. Consequently the element is resilient under pressure applied between the two non foil covered longitudinal faces (that is in the plane parallel to the foil covered faces and perpendicular to the longitudinal axis of the element) . As describe above this resilience is a feature of longitudinally compressed mineral fibre web which is utilised when the element is cut in the orientation described above. Preferably the mineral fibre core has a pleated pattern as a result of being produced by a suitable longitudinal compression process. The longitudinal compression process may be carried out as described in any of the above mentioned patent specifications. The element is preferably cut so that its longitudinal axis is perpendicular to the direction of propogation of the pleats (or parallel to the pleats themselves) . It is generally the case that the product formed by longitudinal compression, especially product having a generally pleated pattern of mineral fibres, and with a density of less than 120 or 100 kg/m 3 , has inadequate self deflection properties, for elements cut from the web which are elongate in the machine direction of the web. However, in the present invention, it has been found that the application of a foil so that two opposite longitudinal faces are bonded to the foil provides the element with a surprising level of resistance to self deflection, when the element is oriented with the foil in either horizontal or vertical direction. Self deflection in an elongate element can be measured by a method in which the element is positioned horizontally, supported under each end, in the desired orientation (eg with foil covered surfaces arranged vertically or horizontally) . The degree of vertical deflection in the centre provides a measure of the self deflection. Preferably the density of the mineral fibre core is in the range 60 to 120 kg/m 3 , more preferably in the range 90 to 100 kg/m 3 . The higher the density, the better the fire performance (the longer the barrier performs in a fire test) . It is generally found that, for a wall cavity fire stop a density of 80-100kg/m 3 is desirable, whilst for an access floor the density can be lower, for instance about 60-70kg/m 3 . The mineral fibre is preferably rockwool . The element of the invention preferably has a length in the range 500 to 1500 mm, most conveniently in the range 750 to 1000 mm. Generally the thickness of the element between the foil covered faces is in the range 60 to 150 mm, most preferably 75 to 120 mm. The height of the element between the longitudinal non-foil covered faces is preferably in the range 50 to 1000 mm, more preferably 60 to 750 mm, most preferably 75 to 100 mm. The invention further provides the use of the new element to form a fire stop in a cavity in a building, preferably a cavity between a floor slab and a real floor or a wall, or between two leaves of a cavity wall, wherein the foil covered faces of the element lie perpendicular to the two major sides of the cavity. It is particularly convenient for the longitudinal elements to be cut on site to the desired shape. It is convenient for a precursor of the element to be provided as a rectangular slab having foil covered major faces. The slab is generally cut into longitudinal elements by cutting parallel slices from the slab. A fire stop is generally required to be longer than a single element and the fire stop is therefore formed by arranging several elements end to end. In order to improve the fire barrier properties still further, the ends of the elements are rebated or otherwise cut, so as to provide overlapping steps, to minimise the effect of a break, especially in the foil, which may allow transmission of smoke. Preferably the precursor slab is provided with appropriate shaping, for instance rebating, at opposite edges of the generally rectangular slab, so that each slice, which forms an element, has shaped ends to provide that overlap. The invention is conveniently put into effect by providing a precursor slab in conjunction with appropriate fixing brackets comprising metal clips having a first end capable of impaling into the non- foil covered side of an element cut from the slab and a second end suitable for fixing horizontally in a wall, as a kit for use on site. In a building method according to the invention, a fire stop is provided in a cavity, and in the method fixing brackets are fixed into a wall forming the first side of a cavity with impaling ends extending substantially perpendicularly from the wall to a distance of at least 50%, preferably about 75% of the eventual width of the cavity, an elongate element which has a height between non foil covered faces of about 1 to 5 mm more than the desired width of the cavity, is impaled through a non foil covered face on the fixing brackets, and the second side of the cavity is subsequently built with the elongate element being subjected to compression during said building. In an alternative method, a fire stop is provided in a preformed cavity. In this method, an elongate element having a distance between non foil covered faces which is in the range 1 to 5 mm greater than the width of the cavity is compressed between the non foil covered faces so that the height between those faces is less than the width of the cavity and is inserted into the cavity and allowed to expand in the cavity into contact with the walls, whereby it is retained in position by friction between the non foil covered faces and the sides of the cavity. In the methods, it is convenient for the elements to be cut on site from a rectangular precursor slab. Thus the distance between non- foil covered faces can be adapted as desired to the width of the cavity. The precursor slab is suitably provided with instructions to ensure it is cut in the appropriate direction to take advantage of the resilience afforded by the length compression of the mineral wool, as described above. In the methods of the invention, it is preferred for a single fire stop to be formed of several elongate elements abutted end to end, in which the abutting ends of the elements are rebated and interlock with each other in the fire stop. Where the fire stop is installed in the cavity of a wall, it is generally arranged in a horizontal orientation. In such an arrangement the cavity is preferably provided with a damp proof course built into the cavity above the fire stop in order to avoid collection of moisture on the upper impermeable foil covered surface of the fire stop. The invention is further illustrated in the accompanying drawings in which: Figure 1 shows a perspective view of one end of an elongate element according to the invention; Figure 2 shows a perspective view of a precursor slab with one elongate element sliced from the slab; Figure 3 is a plan view of a firestep in the cavity between an access floor and a cavity wall; and Figure 4 is a section along line IV- IV in Figure 3. In Figure 1 there is shown one end of an elongate element 1 comprising a mineral fibre core 2 and air impermeable metal foils 3 and 4 covering opposite longitudinal faces of the element 1. The end of the element is rebated by cutting a step generally shown at 5 as indicated. At the opposite end of the element there will be a similar step allowing for co-operation with an abutting element to form a fire stop which is longer than the element itself. The mineral wool core is generally formed of rockwool, in this case having the density of around 90 kg/m 3 . The element has a thickness t in the range 60 to 150 mm, preferably 75 to 120 mm. The width w between the longitudinal non foil covered faces 6 and 7 is in the range 50 to 500 mm, more preferably 80 to 400 mm. The length of the element is preferably in the range 500 to 1500 mm, more preferably 750 to 1000 mm. Foils 3 and 4 are preferably formed of a laminate including a layer of aluminium foil of thickness 25 μm. The laminate includes surface layers of fibreglass scrim reinforcement of weight 93g/m 2 and polyethylene adhesive at 25 g/m 2 . The foils are attached to the core 2 by passing the length compressed cured slab between a set of heated rollers, with polyethylene side facing the rockwool, at a temperature high enough to melt the polyethylene and under a suitable pressure. It may be desirable to apply additional adhesive to the inner face of the foils 3 and 4 and/or to the surface of the mineral wool core, or to adhere a non-precoated laminate using such adhesive. As is shown in Figure 1, the mineral fibre core 2 is formed of fibres 8, whose orientation is generally perpendicular to the foil covered faces 3 and 4. This orientation is achieved by the use of length compression during manufacture of the mineral fibre web. Length compression is achieved in known fashion by the use of sequential series of conveyor rollers or belts with decreasing speed. The difference in speed between the conveyor components at the start of the length compression unit as compared to the end of the length compression unit may be around 3:1. Using a suitable arrangement of conveyors the mineral wool is effectively pleated so as to provide the desired orientation of fibres. The fibre orientation provides good resistance to compression in the direction between the foil covered faces 3, 4 and between the non foil covered faces 6, 7, whilst the adhesion of foils 3 and 4 provide the elongate element 1 with appropriate resistance to self deflection. Figure 2 illustrates how a rectangular precursor slab 9 having continuous foil sheets 13 and 14 covering respectively lower and upper surfaces and having a step 15 cut at each end, is sliced along lines 16, 17 and 18 to form a series of elongate elements 1. Figures 3 and 4 show how a fire stop is provided in a preformed void between a floor formed of concrete floor slabs 20 and a curtain wall 19. The cavity between the floor and the curtain wall is w' in depth, w' being between 1 and 5 mm less than the width w of the elongate element 1. A fire stop is formed of several elongate elements, including 1 and 1 ' arranged with rebated ends 5 overlapping one another . Each element 1, 1', cut for a snug fit to width w is impaled onto metal brackets 21, 22, each of which has a cranked shape shown better in Figure 4. The brackets, spaced apart at distances in the range 400 -500mm, are impaled into the elongate element 1, each bracket extending through more than half (about 75%) the width w of the element. The element is then fitted in to the void, with adjacent elements being tightly butted to one another. The protruding ends of the brackets, now lying on the floor slab 20, can subsequently be mechanically fixed to the floor using appropriate means. Since the width w' of the cavity is less than the width w of the uncompressed elongate element, the element is held in the cavity under compression. Where the elements are to be fitted in masonry wall cavities, the brackets are built into the bed joints of the internal leaf at spacings of about 400-500mm. After the next lift of masonry is completed, the elements are impaled onto the protruding ends of the brackets after which the outerleaf can be continued with suitable damp proof course being built in as necessary above a horizontal fire stop or vertically externally of a vertical fire stop.

Claims: CLAIMS 1. An elongate rectangular cylindrical element having a rectangular cylindrical mineral fibre core and an air impermeable fire resistant foil bonded and substantially covering the surface of two opposite longitudinal faces of the core, characterised in that the core is formed of a single ply mat and has a density of more than about 60 kg/m 3 . 2. An element according to claim 1 in which the fibres of the core are oriented predominantly in a plane substantially perpendicular to the surfaces to which the foil is bonded. 3. An element according to claim 1 or claim 2 in which the foil comprises an imperforate continuous sheet of aluminium, preferably being about 20 micron thick. 4. An element according to any preceding claim which has a resilient compressibility between the two non- foil covered longitudinal surfaces such that the element may be elastically compressed by an amount in the range 1 to 5 mm. 5. An element according to any preceding claim in which the fibres are arranged in a pleated pattern, in which the pleats propagate perpendicular to the longitudinal axis of the element. 6. An element according to any preceding claim which has a length in the range 500 to 1500 mm, preferably 750 to 1000 mm. 7. An element according to any preceding claim which has a thickness between the foil covered faces in the range 60 to 150 mm, preferably 75 to 120 mm. 8. An element according to any preceding claim whose height between the longitudinal non-foil covered faces is in the range 50 to 500 mm, preferably 80 to 400 mm. 9. An element according to any preceding claim in which the mineral fibre is rockwool. 10. An element according to any preceding claim in which the density of the mineral fibre core is in the range 60 to 210 kg/m 3 , preferably in the range 60 to 100 kg/m 3 . 11. Use of an element according to any preceding claim to form a fire stop in a cavity bounded on at least two opposing sides, in a building, preferably a cavity between an access floor and a real floor or wall or between two leaves of a cavity wall, wherein the foil covered faces lie perpendicular to the two major sides of the cavity. 12. A kit comprising an elongate element according to any of claims 1 to 10 and fixing brackets comprising metal clips having a first end capable of impaling into the non foil covered side of the slab and a second end suitable for fixing horizontally in a wall. 13. A kit comprising a cuboidal slab having a cuboidal core of mineral fibre having a density of at least 60 kg/m 3 and covered on its two major faces by air impermeable fire resistant foil and fixing brackets comprising metal clips having a first end capable of impaling into the non foil covered side of the slab and a second end suitable for fixing horizontally in a wall, in which the mineral fibre core comprises a single ply mat. 14. A kit according to claim 13, in which the slab is provided with two opposite rebated edges. 15. A method of providing a fire stop in a cavity in which fixing brackets comprising metal clips are fixed into a wall forming the first side of the cavity, a series of clips being substantially aligned with one another and having impaling ends extending substantially perpendicularly from the wall to a distance from the said wall of at least 50% of the eventual width of the cavity, an elongate element according to any of claims 1 to 11 having a height between non foil covered longitudinal faces of about 1 to 5 mm more than the desired width of the cavity, is impaled through a non foil covered face on the fixing brackets and the wall forming the second side of the cavity is then built with the elongate element being compressed by the said second wall to form a cavity of the desired width. 16. A method according to claim 15 in which the elongate elements are cut on site from a slab as defined in claim 13. 17. A method according to claim 15 or claim 16 in which several elongate elements are abutted end to end to form a fire stop which is longer than the length of a single element and in which the abutting ends of the elements are prerebated and interlock with each other in the fire stop. 18. A method according to any of claims 15 to 17 in which the fire stop is installed generally horizontally and in which a damp proof course is built into the cavity above the fire stop.

Inventors: FRANCIS KENNETH IAN, OSMOND CHRISTOPHER, FRANCIS, KENNETH, IAN, OSMOND, CHRISTOPHER
Applicants: FRANCIS KENNETH IAN, OSMOND CHRISTOPHER, ROCKWOOL LTD, FRANCIS, KENNETH, IAN, OSMOND, CHRISTOPHER, ROCKWOOL LIMITED
Application year: 1998
Main classification: E04B1
IPC codes: E04B1