|
 |
|
| Genesis® Overview |
| Press Releases | On-Line Brochure Release |
|
|
|
|
|
|
| |
TORONTO STAR
July 9, 1998
Pat Brennan, Editor New In Homes
Toronto Star, 1 Yonge St. Toronto, ONFire Performance of Steel Framing for Housing
|
Dear Pat:
The Canadian Sheet Steel Building Institute (CSSBI) is an industry organization representing Canadian Manufacturers of steel building components for over 35 years. Our membership includes the manufacturers of lightweight steel framing (steel studs and joists) which is finding a growing use in residential construction. If you have cause to run articles on house construction and relate to steel products, we would like to offer our services as an information source.
As an item of possible interest, over the past 3 years the CSSBI has been participating in a collaborative industry-government research program investigating the fire resistance and acoustic performance of lightweight floor assemblies.
Other members of this consortium include the Canadian Wood Council, the Gypsum Association, Canada Mortgage and Housing Corporation and the Canadian Home Builders Association.
A similar full-scale testing program of load bearing walls sponsored by this consortium is also under way. All testing and analysis of results has been conducted by the National Research Council of Canada (NRC), Institute for Research in Const- ruction (IRC) in Ottawa.
The results developed in this program are intended for inclusion in the National Building Code of Canada (NBCC) to aid architects and designers in selection the appropriate assemblies for code compliance. This would be similar to the tables already found in the NBCC for lightweight non-load bearing walls.
A final report on the results of full-scale fire tests on floor assemblies has been published. Fire testing follows a number of strict standards and consists of constructing and assembly over a high temperature furnace. The floor is then loaded to a given structural capacity and the furnace is turned on. The time required for the temperature on the floor to reach a critical temperature or the time required for structural failure, which ever is less, determines the fire resistance rating of the assembly.
The results of this testing showed that the lightweight steel floors generally equaled or outperformed their wood joist counterparts under the same test conditions.
I hope that this information on fire performance is of value to any research you may be undertaking on the topic of steel framing for residential construction. Enclosed is one of our technical bulletins on the same topic.
If you are interested in other issues pertaining to the performance of lightweight steel framing, please do not hesitate to Contact KML.
Sincerely,
CANADIAN SHEET STEEL BUILDING INSTITUTE
Steven R. Fox, P.Eng. General Manager
------------------------------------------------------------
Lightweight Steel Framing Technical Bulletin
Volume 1, Number 1
Report on: Fire Performance
On July 2, 1996, a gas stove caused a fire in the kitchen of a steel framed home in Sommerset at Brentwood, CA. The home, built by Innovative Steel Systems, is one in a 2000 home development. The fire caused $75,000 in damages to interior and personal property. In this steel framed home, the flames were contained to the kitchen with smoke damage elsewhere and no structural failure of the steel roof trusses or wall frames occurred.
If this home was of typical combustible construction there would have been additional costs incurred to replace charred members and to chemically treat those charred members that were not replaced to seal in smoky odours.
The firefighters were impressed with the fact that the fire was contained to the hot spot in the kitchen. Developer Sheryl Palmer, V.P. of Marketing and Sales for Sommerset at Brentwood, was not surprised. Steel framing does not add fuel to a fire. This allowed sufficient time for the fuel source, in this case kitchen cabinetry, to burn itself out.
According to fire- fighters the fire reached temperatures of 650 to 7600C (1200-14000F) and yet no structural failure of the steel frame occurred.
The firemen commented that if the structure was of traditional wood frame, the damages would have been more extensive.
An analysis was performed on the steel truss cord and wall studs in the area most affected by the fire. Physical testing showed that the mechanical properties of the members still met the specifications for structural steel studs. The zinc coating on the steel remained intact and in some places there was evidence of alloying with the steel substrate to produce galvanneal, a product commonly used in manufacturing automotive body panels.
As a result of this analysis, none of the framing members needed to be replaced.
In combustible construction, replacement of framing members depends on the amount of charring in that member. This is generally performed by surface inspection and can often be subjective, thereby compromising the structural integrity of the building.
In October 1996, in the western community of Tucson, AZ, a fire ripped through a studio/garage that was being built with lightgauge steel framing and straw bales.
A fire began when a worker's torch ignited the straw bales in one corner of the structure. One can only imagine how quickly the fire spread fuelled by the unfinished straw bales and plywood sheathing.
Straw bale construction is understood to be fire resistant because compressed straw bales in finished walls leave little room for oxygen, which is needed for a fire.
Owner/ Builder Ron Carswell, has successfully built several similar structures which uses lightgauge steel for posts and beams to carry the loads and straw bales to infill the space between the frames. Ron is an avid proponent of straw bale construction.
Since this building was not yet finished the fire spread quickly. When Tucson fire response teams arrived the structure was fully engulfed and a decision was made to let the fire burn itself out. The fire reached temperatures of 6500C (12000F) which was hot enough to severely crack the concrete floor slab. When the smoke cleared the steel framing was still standing.
Doug Emans, assistant fire chief at the scene was surprised. He said "a similar wood structure would have collapsed". Another fire fighter commented that wood would have been "toast".
In fact 2' x 6' lumber used to frame around some of the openings was just that. With the framing still standing it greatly reduced the fireman's task of checking the debris to ensure all hot members were out.
The insurance claims adjuster was also impressed. In all of his exper- iences of inspecting the aftermath of fires he couldn't believe the roof trusses and walls were still standing after all the sheathing had burned off.
The performance of any light framing material in a fire will depend on the intensity of the fire. What one can count on in the case of steel framing, is that this material will not add fuel to a fire. In principle this would prevent propagation of fires. Lightgauge steel framing members that have been exposed to extreme conditions and that have failed are easily identifiable and hence replaced, which is not the case with combustible framing members.
Any smoke adhering to steel framing members is washed off with a mild detergent while chemical treatment is required to seal the odour in combustible members.
In the Brentwood and Tucson homes the containment of the fire can be attributed to the non-combustible steel framing used in building the home.
Not having to replace the framing members contributes to lower damage costs, which should help the insurance industry to evaluate the possibility of lower premiums for steel framed homes that are fully finished or under construction.
Photos: A similar wood structure would have collapsed. Steel framing still standing after the fire. Courtesy of American Studco.
|
|
