FIRE PROTECTION FOR FLOORS AND CEILINGS

Abstract: Rigid slabs (19) of mineral wool or other firestop material are fitted between the joists (10) of wooden floors and ceilings, any gaps between the slabs (19) being filled with a pourable settable firestop material (21), and the slabs (19) rest upon metal or other refractory supports (18) carried by metal or other refractory brackets (16) or plates (22), so that the slabs (19) remain in place and the floor or ceiling stays stable for a long period in the case of fire.

Description: This invention relates to the fire protection of floors and ceilings, especially those of conventional wooden construction, and provides an assembly or kit of parts for installation in or under existing floors and ceilings, as well as for inclusion in the original construction of floors and ceilings, for fire protection purposes. The fire protection arrangements according to the present invention are especially useful, as they can be used both for installation during the construction of new buildings and also during the refurbishment of existing buildings. Thus, the invention provides a convenient and satisfactory means for raising the standard of fire-proofness of any building. The provision of means for delaying the destruction of building components by fire is highly important. Any system of fire protection which enables the walls, floors, ceilings and/or roofs of buildings to remain stable for a substantial period, when there is a fire, can provide time for the occupants to leave or be taken from the building, so that serious injury or loss of life can be avoided. It is generally reckoned that any fire protection system is satisfactory if it enables a building or its components to remain stable for at least minutes, even if it includes substantial amounts of wood. The present invention provides a fire protection system, including a kit or assembly of fire-proofing parts, which enables a conventional wooden floor to remain stable for a period substantially longer than 30 minutes and, in many cases, for a period of 60 or 90 minutes or even more. Also, the invention enables conventional wooden floors to remain both stable and at a temperature low enough for safe contact for such extended periods of time. Thus, a wooden floor equipped with the fire protection system of the invention can remain sufficiently unaffected by a fire in the underlying space or rooms to enable even chair-bound or bed-ridden occupants of the room or rooms on that floor to be taken out to safety. A conventional wooden floor includes wooden joists spaced at equal intervals and supported at their ends and possibly between the ends on footings or walls below, having wooden boards secured to their upper surfaces, cross-bracing or nogging pieces of wood at spaced intervals and, possibly, wooden laths attached to the underside of the joists and forming a framework for suporting slabs of firestop material and a plaster ceiling of the room or rooms of the building storey below the floor. In the case of a ground floor, no components are attached to the undersides of the joists, in normal practice, while in the case of the uppermost storey of a building, often no boards or other components are attached to the upper sides of the ceiling joists. NL-A 7 808 451 discloses a ceiling or floor arrangement in which slabs of firestop material are located between the joists. The slabs are supported between the joists by means of steel sections extending across the width or length of the floor or ceiling. Further, fire-resistant supporting means are located between the steel section and the joists. However, the ceiling or floor arrangement is formed as one with the firestop material and the steel sections necessarily forms an integral part of the supporting structure for the joists and ceiling/floor. EP-A-0 028 893 discloses a heat insulating roof structure in the form of an inter-purlin system, the purlins of which have a variety of cross-sectional configurations and are sheathed by an insulating sleeve. Again, the roof structure is orginally formed with the heat insulating properties and the disclosure of this document does not suggest ways of improving the heat insulation of a previously constructed roof structure. According to one aspect of this invention, a fire protection arrangement is provided for use with a floor or ceiling including combustible joists, comprising one or more slabs of firestop material for location between the joists and support means for supporting the one or more slabs and formed of metal or other refractory material, characterised by attachment means for providing a supporting attachment of respective ends of the support means to respective side walls of the joists such that, in use, the support means extend from said side walls. Thus, an assembly or kit of parts for installation in a floor or ceiling can be provided comprising self-supporting fire stop material units and refractor support means for attachment to the joist and carrying the slabs. According to a preferred way of putting the invention into practice, thick slabs of mineral wool or other firestop material are located between the joists, in a substantially contiguous manner, upon metal (preferably steel) supports secured at their ends to the upright sides of the joists and wooden components of the floor, such as cross-bracings, are encased, at least to the same depth as the thickness of the slabs, in a pourable firestop composition. Preferably, brackets of sheet steel or, in general, any suitably strong refractory material are secured to the joist sides and the supports are T-section steel members which are carried by their ends upon the brackets. Also, it is preferably for the supports to be located where butt joints are formed between adjacent slabs, so that each support carried the edges of two adjacent slabs. These butt joints also are preferably sealed with a pourable firestop compound. The invention thus puts into practice a principle of fire-proofing or fire protection whereby, except for the joists themselves, a substantial depth of firestop material, amounting typically to 1/3 to 2/3 of the height of the joists, is disposed over the entire area of the floor or ceiling, i.e. the area beneath the boards in the case of a floor. In the event of a fire below the floor, that is, a fire in the room or rooms below or a fire under the ground floor of a building, a very large depth of wood in the joists has to be consumed before the flames can pass from below to above the floor. Moreover, these parts of the joists are in abutting relationship with firestop material, provided e.g. either as slabs or as a pourable composition, so that the firestop material also protects a substantial depth of each side surface of the joists. In order that the invention may be readily understood, preferred forms of the fire protection arrangement of the invention are shown, by way of illustration only, in the accompanying drawings, in which: Fig. 1 shows a conventional wooden floor, partly broken away, in diagrammatic perspective view; this can typically be the floor of an upper room or storey in, for instance, a hospital or a residential home; Fig. 2 shows the main components of a kit or assembly of parts, also in diagrammatic perspective view, which can be supplied and installed in an existing or new building, in order to put into use the fire-protection arrangement of Fig. 1; Fig. 3 shows a fragmentary vertical section through a wooden floor or ceiling, provided with a variant of the fire-protection arrangement shown in Figs. 1 and 2. The floor shown in Fig. 1 is constructed from: (a) wooden joists 10, e.g. of G.S, grade timber, 225 mm × 50 mm, equally spaced at 400 mm centres and having a span of e.g. 4.0 to 6.0 m; (b) wooden boards 11 on the upper surfaces of the joists 10, of straight-edged timber, e.g. 100 mm × 19 mm; (c) hardboard sheets 12, e.g. 3.1 mm thick, nailed to the boards 11; (d) herringbone braces or nogging pieces 14, of 50 mm × 50 mm softwood, nailed to the joists 10 at mid-span; (e) a ceiling, e.g. wooden laths and plaster (not shown) or further hardboard sheets 15, nailed to the undersides of the joists 10. According to a first preferred embodiment of the invention, the floor (a) to (e) consisting of the parts 10 to 15 is provided with a fire protection system which comprises: (f) steel angle sections 16, 100 mm long (18 swg) nailed (17) to each side of each joist 10 at 500 mm centres, each angle section 16 or bracket having an upright part 16a attached by a nail 17 to the joist 10 and a horizontal part 16b, together with a slot 16c made centrally in the part 16b, so that the slot 16c in one bracket 16 is aligned with that of the opposing bracket 16 on the next joist 10; (g) steel T-section supports 18, 320 mm long (20 swg) at 1.0 m centres, each support 18 having the upright part 18a of its T-section shape located in the slots 16c of the associated brackets 16, with the undersides of its horizontal parts 18b resting upon the bracket parts 16b; (h) mineral wool slabs 19, e.g. of the firestop material available under the Regd. Trademark "Corofil"C 144, 80 mm thick and of 110 kg.m³ nominal density; these slabs 19 are cut so that each is a firm push fit between the joists 10 and each rests upon the brackets 16 and the supports 18; each slab 19 has a maximum length of 1.0 m and the butt joints, such as indicated at 20 in Fig. 1, between adjacent slabs 19, are preferably located upon the supports 18; (i) a pourable firestop composition 21, preferably of a kind which can be set solid on installation, e.g. the firestop composition available under the Regd. Trademark "Corofil" G.P.G., is filled completely around the bracings or nogging pieces 14, in the gap between the opposed ends of the slabs 19, from the upper surface 22 of the ceiling 15 to the upper surfaces 24 of the slabs 19. The components (f) to (i) of the fire-protection arrangement of the invention are also shown in Fig. 2. It will be understood that all the dimensions and other details of the components (a) to (e) and of the components (f) to (i), mentioned above are merely illustrative and can be varied over wide limits, depending upon the principle of construction of the building and the preferred way of putting the invention into practice. The chain-dotted line 25 (Fig. 1) indicates the upper level on the side of each joist 10 of the installed fire protection system; as each slab 19 rests only slightly above the ceiling surface 22, upon the brackets 16 and supports 18, the distance A from the bottom to the top of the slabs 19 and of the compound or composition 21, i.e. the thickness of the fire-proofing assembly, is a substantial proportion of the height B of the joists 10; in the preferred embodiment where the components have dimensions such as are indicated above, by way of illustration, A is from 1/3 to 2/3 of B; specifically, A is approximately the slab thickness of 80 mm, while B is the joist height of 225 mm. Referring to the embodiment of the invention shown by way of illustration in Fig. 3, instead of using angle brackets 16 secured at their ends to the sides of the joists, 10, flat refractory, e.g. metal and preferably steel plates 22 are secured as required, for instance to the undersides of the joists 10. Cross-bracings or other wooden components of the superjacent floor located between the joists 10 (not shown in Fig. 3) can again be at least partially encased in a pourable firestop composition, if required, which can be located from above before the boarding of the upper floor is put into place or after it has been removed in the appropriate places, for this purpose. The fire protection system of this embodiment of the present invention is thus suitable for use in situations in preference to a system according to embodiments of Figs. 1 and 2 while still fulfilling the same general and advantageous principle that a substantial depth of firestop material is disposed over the entire area beneath the boards 11 of the floor, save for the joists 10 themselves. Fig. 3, in which the same reference numbers are used for the same parts as in Figs. 1 and 2, shows diagrammatically in vertical section a suspended floor, comprising wooden joists 10, shown in sectional view, with wooden floor boards 11 attached to the tops of the joists and, at 19, mineral wool slabs located in abutting relationship with the sides of the joists 10 and, if necessary, with one another; where the slabs 19 butt one another, steel supports, e.g. of inverted T-section, can extend between the joists 10; except for being upside-down, these supports can be like those shown at 18 for the butt joints 20 between adjacent slabs 19, in the embodiment of Figs. 1 and 2. In order to support the firestop slabs 19, flat steel supporting plates 22, for instance portions of 18 swg galvanised sheet steel measuring 150 × 100 mm, are attached to the undersides of the joists 10, for instance with twist nails, so that each plate 22 projects to both sides of the joist 10, as required, thus providing a projecting support for the associated part of the edge of each slab 19. Where a conventional floor such as is described above, comprising the components (a) to (d) and, if appropriate, (e), does not have a fire protection system and if there is a fire in the room below, the floor will fail, i.e. burn through and/or collapse, in perhaps 10 to 20 minutes; in contrast, where the floor is associated with a fire protection arrangement according to this invention, such as decribed in conjunction with Figs. 1 and 2 or Fig. 3 of the drawings, a much longer period will elapse. In a test carried out, with an imposed load upon the floor of 2.35 kN/m², i.e. the load which represents the maximum stress on the joists 10 according to BS 5268, Part 2, 1984, it was found that a fire in the room below caused the "ceiling", i.e. the hardboard sheets 15 to fall away, but the slabs 19 remained in position throughout a heating period of 108 minutes; the floor collapsed after another 2 minutes. The surface of the floor registered a temperature of 30°C after 30 minutes, so that people could safely walk across the floor, e.g. in assisting occupants to leave, while the mean and maximum floor temperatures recorded at the end of the 108 minute heating period were 56° and 64°C respectively. Under BS 476, Part 8, 1972, the floor of the invention thus demonstrated a stability (i.e. 80% of the heating period) of 86 minutes and integrity and insulation times of 108 minutes. Instead of becoming unstable and/or collapsing after about 10 to 20 minutes, the invention allows floors to remain in position for well over 1 hour; a fireman with suitable wearing apparel and breathing apparatus can safely enter and leave such a room for up to approximately 1½ hours after the onset of the fire in the room below. The present invention puts into practice a fire-proofing principle in which firestop material is disposed within the floor or ceiling structure over substantially the entire available area, in the spaces between the joists which are usually left empty. Moreover, the firestop material used is self-supporting to a substantial extent, by being either in the form of rigid slabs or in a pourable form which, after location in place, preferably sets to a solid state. When a floor or ceiling equipped with firestop material of this kind is subjected to fire, the firestop material stays in place for extended periods to time and, as the only parts of the floor not filled with the firestop material are, substantially, the underneath surfaces of the joists, the fire is very largely contained under substantial areas of rigid self-supporting and stable refractory material. The only parts where this material is absent are the joists per se and these resist consumption by the fire for long periods, because of their depth. In addition, all the components used specifically to support the firestop slab materials are refractory, typically being steel or some other fire-resistant metal. Even if the floor components undergo relative movement during a fire, for instance as the joists twist or buckle, the brackets 16 or the plates 22 and the supports 18 carried upon them, as well as the fixing means (e.g. the nails 17), remain properly assembled and thus continue to support the slabs 19 and the poured and set firestop composition 21. The invention thus consists, in effect, in fireproofing a floor or ceiling by filling the spaces between the joists with firestop material and securing the firestop material in place by fire-resistant supporting means which remain substantially stable even in the presence of fire.

Claims: A fire protection arrangement, for use with a floor or ceiling including combustible joists (10), comprising one or more slabs (19) of firestop material for location between the joists (10) and support means (18) for supporting the one or more slabs (19) and formed of metal or other refractory material, characterised by attachment means (16) for providing a supporting attachment of respective ends of the support means (18) to respective side walls of the joists (10) such that, in use, the support means (18) extend from said side walls. A fire protection arrangement according to claim 1, in which the slabs (19) are arranged and dimensioned so as to be located between the joists (10) in a substantially contiguous manner and the support means comprise steel or other refractory metal supports (18) secured at their ends to brackets (16) for attachment to the joists and in which other combustible components of the floor or ceiling are encased, at least to the same depth as the thickness of the slabs (19), in a pourable and preferably settable firestop composition (21). A fire protection arrangement according to claim 2, in which butt joints are formed by adjacent slabs (19) and the supports (18) are positioned where the butt joints are located, so that each support (18) carries the edges of two adjacent slabs (19). A fire protection arrangement according to claim 2 or 3, in which the support means (18) comprise steel members of T-shape in section. A fire protection arrangement according to claim 3 or 4, in which each bracket (16) includes an upright part (16a) for attachment to a joist (10) and a horizontal part (16b) and the T-section support (18) has the ends of its upright portion located in aligned slots (16c) provided in the horizontal parts (16b) of the brackets (16) on adjacent joists (10) A fire protection arrangement according to any preceding claim, in which a pourable and settable firestop composition is disposed in the butt joints formed by adjacent slabs (19).

Inventors: ASHLING, GEOFFREY EDWARD, PEBODY, JOHN, WALKER, ANTHONY RONALD
Applicants: PRE-FORMED COMPONENTS LIMITED
Application year: 1986
Main classification: E04B1
IPC codes: E04B5, E04B9, E04D13