Patent Application
20120240504
The invention relates to building construction and, in particular, to a method and materials for inexpensively fireproofing floor joists.
Recent experience has revealed that uncovered lightweight joist construction in residential properties, while adequate in ordinary circumstances, may be susceptible to early structural failure in the event of a fire. This circumstance poses a severe risk to occupants and to firemen or other rescuers who might walk onto a floor area compromised by a fire below and fall through the weakened area. There exists a need for a practical, inexpensive way of protecting lightweight joists to extend the time that they can withstand a fire occurring below. Sprinkler systems are expensive to install, require periodic maintenance and testing and are susceptible to freezing. A conventional drywall ceiling requires taping and eliminates ready access to the joist space for inspection, repair and alteration of utilities, or other purposes. Lightweight joist construction typically involves engineered wood joists. These engineered wood joists, most commonly, are in the form of a wood I-beam having an OSB web and lumber flanges, or a parallel chord truss made of metal plate connected lumber elements.
The invention provides a method and system for protecting residential floors, for a limited time, from a fire originating below the floor. The invention utilizes conventional materials in a novel manner to achieve a level of protection at relatively low cost while affording additional benefits.
More specifically, the invention combines certain suspended ceiling grid components with fire-rated drywall panels to construct a fire barrier layer or ceiling. The fire barrier layer protects lightweight floor joists from the heat and flames of a fire existing below the floor. The barrier layer can afford protection for a period of time of, for example, 30 minutes.
The drywall panels of the system are carried on main tee runners arranged in parallel on 2 foot centers as contrasted from typical four foot centers of a conventional ceiling construction. The panels are supplied at or are field cut to a width slightly under the 2 foot dimension so that they fit between adjacent runners. Unlike the practice in conventional ceilings, where a grid is established with numerous cross tees or runners between main runners, few if any cross runners are used in the practice of the invention. Also, unlike conventional suspended ceiling construction, the drywall panels are supplied in lengths of 8, 10 or 12 feet, for example. This panel length eliminates the use of most if not all cross runners, depending on the dimensions of the floor area being protected.
Where a dimension of the floor area is longer than a panel, a cross tee can be used between the ends of two panels. This technique eliminates the need to tape what would otherwise be an exposed joint between these panels. Where the plane of the barrier layer is penetrated by utilities, a panel can be cut across a transverse line that is tangent to the penetration, and a cut-out can be made for the penetrating object. A cross tee can be used to support the panel at the transverse cut.
From the foregoing, it will be seen that the invention provides an economical fire barrier layer using conventional materials with minimal material and labor costs. The barrier layer can reduce sound transmission to the space above the protected floor. The drywall panels as well as the grid runners can be painted after they are installed. Whether painted or not, the panels can improve light reflectance in the space below the fire barrier layer.
Shown in
Wood lightweight joists as described have many recognized advantages over solid sawn lumber but can, unfortunately, have a serious disadvantage in the event they are exposed to a fire from below for a relatively short period. Some studies have shown lightweight wood joists failing after only 6 minutes as compared to 30 minutes with conventional solid sawn wood joists.
The invention provides a low cost fire barrier to protect a residential floor from early destruction when exposed to a fire from below. A typical situation where a fire could quickly involve floor joists in a basement of a residence exists where the joists are not covered with a finished ceiling.
The fire barrier layer of the invention utilizes standard building materials and components to minimize cost, complexity and installation labor. The invention uses basic suspended ceiling grid members, but departs from the norm by eliminating, for the most part, a rectangular grid. Instead, where penetrations are not required, only main runners are regularly used and cross runners are only used when the width of a room or section of a basement is too large to be spanned by a single panel of the invention, normally 8, 10 or 12 foot in length.
Referring to
An inexpensive way of attaching the tees 21 to the joists 11 is to set a nail into a lower face 23 of a joist, loop a conventional hanger wire around the nail, and then bend the nail over to lock the wire with a nail. The suspension wire, shown at 24, is looped through one of the preformed holes in a bulb 27 or web 29 between the bulb and a lower flange 26 of the grid tee 21 and is then twisted on itself in a conventional manner to fix the tee at a desired elevation. A spacing of 3 or 4 inches from the lower face 23 of a joist 11 to the lower flange 26 of a tee 21 is preferred. This spacing enables a tilted panel 22 with dimensions discussed below to be assembled between adjacent grid runners 21 from below the plane of the runners.
If desired, metal clips can be designed to be attached to the joists 11 and to be snapped onto the bulbs, designated 27, of the tees or runners 21. Another approach is to screw the tees 21 to sheet metal brackets attached to the joists 11. In the illustrations of
Fireproof drywall is commercially available in sheet form having dimensions of 4′×8′, 10′, 12′ or even longer. While a standard fireproof drywall sheets can be used to practice the invention, such sheets are slightly too wide to be conveniently cut into panels having widths of 23¾″ wide. Moreover, standard drywall sheets have tapered edges along their long dimensions. The fire barrier panels 22 of the invention are more conveniently made by splitting fireproof drywall sheets specially made with a width of 47½″ and without tapering.
Such drywall sheets when split in half, normally at the installation site, yield panels that are 23¾″ wide and are ideal for suspending on the conventional tees 21 fixed at 2′ centers. These special width fireproof drywall sheets can have standard 8, 10 or 12′ lengths.
With the main runners or tees 21 suspended in place, the drywall panels 21 can be assembled onto the tees. This is accomplished by tilting one long edge of a panel up into the space between a pair of adjacent tees 21 as far as possible so that the lower opposite edge of the panel can be raised past the flange 26 of the close by tee and then shifted back onto the bypassed flange. Following this, the upward edge can be lowered in place. This assembly maneuvering of the panel 21 is analogous to that typically used when installing suspended ceiling tile on ceiling grid.
Manufacturing facilities for producing dimensional fire-rated ⅝″ drywall can be easily modified to make the slightly narrower non-tapered 47½″ wide preferred panels 21. Standard main tees are joined end-to-end where a floor dimension is larger than say 12′.
Where sections of a basement or area under a floor are larger in dimensions than available with a panel, e.g. beyond 8, 10, or 12′, a cross tee 36 (
Where objects such as pipes and ducts penetrate the plane of the barrier layer 16, a panel can be cut such that it has an edge that is tangent to and cut out for the object. A cross tee can be used to bridge the joint between the cut edge and a complementary panel on a side of the object opposite that of the first panel. The fireproof drywall panels 22, and optionally for expediency, the tees 21 can be painted. This will improve the light reflectance of the panels 22 over their natural reflectance. The fire barrier 16 moreover serves to reduce transmission of sound from the basement area to the space above the floor construction 10.
It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. For example, in geographic regions where metric units are prevalent, the dimensions given above are convertible to their metric equivalents. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.
