Old Fire Retardant Treated Lumber


I have recently heard of a problem with fire-retardant-treated wood (FRTW) trusses that were manufactured and installed in 1965-1980. I was searching for more information, since my job involves the protection of property in our member school districts. I had heard that the trusses make of FRTW during that time period can or will become corrosive to the hardware and the trusses will fail.


Currently there are no widespread problems with old FRT treated trusses. It would be wise, however, to do some random inspections of the roof structures to see if there is anything that may be a concern. Alert SBCA if there is a concern based on the random inspections. We will work with you to ensure that there is a more thorough inspection process for these types of buildings that use trusses.

We forwarded your question to Forest Products Laboratory to get their current take on this issue. Robert White, Project Leader of Wood Preservation and Fire Research, told us: “Given the dates, it would appear that the feedback person is referring to the old hygroscopic FRT problem. I have not had inquiries on this problem that I recall. As with the thermal degrade problem, reformulation and new test method/performance criteria reduced the problem.” For more information on fire-retardant-treated wood, refer to section 20 of SBCA’s Metal Plate Connected Wood Truss Handbook, which includes an article written by Jerry Winandy, a research scientist with the U.S. Forest Products Laboratory (FPL.

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