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Construction Concerns: IBC 2021 Heavy Timber Proposal During Construction Before Drywall and Sprinklers

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Construction Concerns: IBC 2021 Heavy Timber Proposal During Construction Before Drywall and Sprinklers

September 28, 2019 by Steve Conboy

Why would anyone take additional risk now that this movement is well underway when we have had 20 high density housing projects burned down during construction from suspicious ignition all still under investigation in 2019. We all understand char and drywall but the question is what will slow down a arson attack with fuel during construction. M Fire has the cost effective solution and testing to make Mass Timber even safer by making it Class A. We have no fire history on any mass timber buildings and since its wood perception is 9-10th of the law probably driving your risk premiums higher than they need to be. As evidenced by the experiences early adopters in Portland, Ore. and Seattle, architects and developers in the U.S. are going to continue to follow the examples of their counterparts in other parts of the world in designing and building taller structures that make extensive use of CLT. Because of that, fire service leaders in the U.S. must understand this construction trend and become more involved in the revisions to building and fire codes as they relate to tall timber construction.

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Why would anyone take additional risk now that this movement is well underway when we have had 20 high density housing projects burned down during construction from suspicious ignition all still under investigation in 2019. We all understand char and drywall but the question is what will slow down a arson attack with fuel during construction. M Fire has the cost effective solution and testing to make Mass Timber even safer by making it Class A. We have no fire history on any mass timber buildings and since its wood perception is 9-10th of the law probably driving your risk premiums higher than they need to be.

As evidenced by the experiences early adopters in Portland, Ore. and Seattle, architects and developers in the U.S. are going to continue to follow the examples of their counterparts in other parts of the world in designing and building taller structures that make extensive use of CLT.

Because of that, fire service leaders in the U.S. must understand this construction trend and become more involved in the revisions to building and fire codes as they relate to tall timber construction.



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HOW FIRE SAFE IS CLT?

In 2000, one of the first research studies, Timber Frame 2000, was conducted on the use of CLT for a structure of six-stories. The study was a partnership between the British Research Establishment and Chiltern International Fire, and jointly sponsored by the U.K.'s timber frame industry and the U.K.’s Department of the Environment, Transport and the Regions.

The U.K. timber industry saw a desire to build structures up to five or six stories using light timber, but building codes limited timber buildings to three stories. This prompted a series of tests on a six-story light timber framed building.

Results of those tests were used to demonstrate that light timber frame buildings could meet the functional safety requirements that would be required for non-combustible steel or concrete buildings. The test had two key objectives.

The first was to evaluate the fire resistance of a multi-story timber frame building subjected to severe natural fire exposure, particularly structural integrity or loadbearing capacity and compartmentation or the prevention of fire spread from the apartment of fire origin. The second was to provide data to help develop fire engineering design principles for medium-rise timber frame buildings above four stories.

The six-story test building contained 24 apartments (four per story). The designated fire test compartment was one of the two bedroom apartments on the third story.

The test fire was ignited in the living area of the apartment and progressed to flashover after about 24 minutes. Peak temperatures in the apartment reached 1,000 C and remained at or close to this level until the test was stopped after 64 minutes, having exceeded the planned termination criteria. Researchers used an array of instrumentation throughout the test building to collected fire performance data. Analysis of that data led researchers to these five conclusions.

The performance of the complete timber frame building subject to fire is at least equivalent to that obtained from standard fire tests on individual elements. Fire conditions in the living room represented an exposure approximately 10 percent more severe than a standard 60-minute fire resistance test. The standard of workmanship (particularly in the installation of plasterboard or sheetrock) is a critical component to the necessary fire resistance. Correct location of cavity barriers and fire stopping is important in maintaining structural integrity. Vertical flame spread from floor to floor via windows needed to be addressed. The results of the study prompted changes to the prescriptive code in the U.K. to increase the height limit to six stories for buildings using CLT structural elements.

In Canada, FPInnovations tested CLT panels, as walls and floors, to demonstrate that the panels had a certain level of fire performance comparable to non-combustible building elements like concrete.

The tests showed the walls and floors could be designed for up to three hours of fire resistance, in many cases exceeding the code requirement for structural element fire resistance ratings.

The researchers presented the study’s results to the Canadian code council and requested changes in the building codes based on the demonstrated performance through fire testing. Thus, the use of CLT has been adopted into the prescriptive building codes in Canada.

FUTURE OF TALL TIMBER CONSTRUCTION IN THE U.S.

To date, the building codes in Europe tend to have taller height allowances compared with the U.S. This makes the approvals process quite a bit easier across the pond, but the prescriptive limit isn’t a deal-breaker.

For example, the height limit in Australia is capped at three stories for wood buildings, yet Australia recently built the tallest modern timber building in the world.

How? In an interview for Arch Daily in March 2014, Robert Gerard, a licensed fire protection engineer in California, said, “The primary difference in terms of approvals, I’d say, is there’s a greater understanding of timber fire safety risks in those regions, resulting from research and testing and educating building authorities. This is something we’re currently working on in the U.S.”

The building codes in the U.K. and Australia are a bit different than those in the U.S. The codes in those countries make greater use of performance requirements and rely less on prescriptive regulations. Instead, building codes in those countries rely more on the use of functional objectives.

Functional objectives are fire safety principles that apply to all buildings regardless of building material. When code enforcement officials, architects and developers agree that the functional objectives have been satisfied, this allows greater flexibility in the building material and design.

It is this difference between building codes in the U.S. and countries such as Australia that has generated such interest for tall timber construction and a greater degree of acceptance in other countries.

If you are an Owner, Builder or Insurance Risk Underwriter of a Mass Timber contract Steve Conboy for a copy of his White Paper and testing why take the risk its not worth it.

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