GB2207449A

GB2207449A - Flame proof joints in plasterboard cladding

Info

Publication number: GB2207449A
Application number: GB08718155A
Authority: GB
Inventors: John Keen
Original assignee: Am & S Europ
Current assignee: Am & S Europ
Priority date: 1987-07-31
Filing date: 1987-07-31
Publication date: 1989-02-01
Also published as: GB8718155D0

Abstract

Joints beween sheets of plasterboard 5, 6 used to form an inner cladding of a metal-framed building wall are covered, on the side remote from the interior, by means of composite non-load-bearing members 11 of plaster 11b and metal 11a, which serve to prevent fire reaching the structural metal members if the joints open. <IMAGE>

Description

Improvements in or relating to the lining of metal framed buildings This invention relates to the lining of structural assemblies based on metal members.

In U.K. patent specifications 2,119,828 and 2,119,889 we have described and claimed a wall for a metal-framed building, based on vertical and horizontal rolled-steel sections. The outer surface of the frame is protected from the outer atmosphere by an heat insulating cladding of e.g. mineral wool or plastics foam. The inner surface of the metal frame is normally clad with sheets of plasterboard or similar inert material.

The relatively thin-gauge steel sections used in such a structural framework are vulnerable to heating effects from fires in the rooms of such buildings; and must be protected from direct contact with flames. Where the frames are clad internally with plasterboard, this is normally in the form of sheets, usually fitted so that an unbroken surface is provided between ceiling and floor of the room, but with vertical joints between individual sheets, at intervals along the lengths of the walls.

Such sheets are usually fixed to the metal frame members by means of recessed self-tapping screws. The vertical joints between individual plasterboard sheets are normally supported and backed by studs i.e. vertical load-bearing structural members of metal.

However it has now been found that a single layer of standard plasterboard (as used in timber-framed constructions) is inadequate to protect the relatively light-gauge steel frames; the wallboards showing a tendency to disintegrate when subject to standard fire-resistance tests required by U.K. Building Regulations.

Conventionally, this problem has been overcome by applying two superimposed layers of plasterboard, with the sheets arranged so that the joints between the sheets are staggered. This arrangement provides adequate protection, but is very costly and also increases the weight of the walls.

A form of gypsum plasterboard incorporating glassfibre and other additives, has been developed to provide improved fire resistance. It is desired to use this material in single layer application for steel framing.

Unfortunately, the glassfibre inclusion within this improved material tends to cause shrinking across the width of the board. This can result in the edges of the sheets at the vertical joints pulling apart, thus opening gaps in the lining and exposing the steelwork to the fire.

Whilst it is possible to secure the joints (by additional screws, adhesives, etc) so that they are restrained from opening, this sets up tensile stresses within the boards and may well cause them to crack elsewhere; thus again exposing the steel to the fire at a different point.

We have devised a means by which a single layer of the improved plasterboard may be used and the steelwork protected from the internal fire.

This invention consists in a wall for a metal-framed building, wherein a frame-work of vertical and horizontal metal structural members is interposed between inner and outer cladding sheets and the inner cladding is composed of a plurality of sheets of plasterboard or similar refractory sheet material which abut at joints; characterized in that non-structural composite members of metal and refractory material are arranged to cover said joints on the side remote from the interior of the building.

The composite members will normally be non-load-bearing and have an inner face of plaster-and an outer face of metal.

The edges of the plasterboard cladding may be lightly secured to the plaster face of the composite member e.g. by screws passing through into the steel backing.

With this arrangement, shrinkage of the improved plasterboard sheet, with consequent joint opening, is no longer important. The gypsum face of the composite stud protects the steel framework from the effects of the fire.

This solution, permitting a single layer of lining, is less Costly than the double thickness alternative, and is lighter in weight.

The invention will now be described in more detail by reference to the two accompanying figures of drawing in which FIGURE 1 shows a section through a wall-board joint according to the prior art (not according to the invention) and FIGURE 2 shows a section through a wall board joint according to this invention as cut by a horizontal plane.

With reference first to Figure 1, the steel frame is made up of members 1, 2 and 3 with wallboards 5 and 6 attached to inner member 2 and abutting at butt-joint 7. As shown screws 8 and 9 are employed to fix sheets 5 and 6 to structural member 3.

In this form of construction, in a fire situation, the boards 5 and 6 are subject to shrinkage across their widths. This results in joint 7 being widened and the underlying steel members 2 and 3 being exposed to the fire.

Turning now to Figure 2 showing a construction according to this invention, structural steel-work members 1 and 2 are bridged by a mid height bracket 10 which is screwed to front and rear members 1 and 2 and carries a composite non-structural member 11 recessed within bracket 10 and attached thereto by means of screws. The composite member 11 is made up of a steel channel lla and a plaster insert llb, which serves to cover a joint 7 between plasterboards 5 and 6. These boards are screwed to the composite member 11 by screws 8, 9 passing through both plaster and steel layers of the composite member.

In this form of construction fire is prevent from reaching the steelwork, if joint 7 opens, by the interposition of the plaster insert llb between the wallboards and the structural steel members 1, 2 and 10.

Claims

1. A wall for a metal-framed building, wherein a frame-work of vertical and horizontal metal structural members is interposed between inner and outer cladding sheets and the inner cladding is composed of a plurality of sheets of plasterboard or similar refractory sheet material which abut at joints; characterized in that non-structural composite members of metal and refractory material are arranged to cover said joints on the side remote from the interior of the building.

2. A wall as claimed in claim 1 wherein the composite members have an inner face of plaster or similar refractory material and an outer face of steel.

3. A wall as claimed in claims 1 or 2 wherein the composite members are attached to structural metal members, of the framework.

4. A wall as claimed in claims 1, 2 or 3 wherein the joints are vertical.

5. A wall as claimed in any preceding claim wherein the plasterboard sheets are lightly secured to the plaster face of the composite member by suitable fixing means.

6. A wall for a metal framed building substantially as hereinbefore described, with reference to Figure 2 of the accompanying drawings.