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Fire-Retardant Wood Framing 2

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abusementpark

Structural
Dec 23, 2007
1,087
Any there any important structural considerations when using Fire-retardant wood framing?
 
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Fastener corrosion, potential wood embrittlement. Older formulations were really bad, but they have improved. Jury's still out on long-term effects of heat/moisture, particularly in attics.
 
I would think it'd be appropriate to use the Incision Factor - although I'm fuzzy on the actual application process of the FR so maybe it's not.

Like Ron said, a lot of light-gauge connectors have specifications where a maximum copper/preservative content of wood is stated, I bet the same spec exists for contact with FR lumber.

 
Use caution against the use of any FRW product in environments exceeding 150° F (down rated up to 180° F) and plywood exceeding 170° F. Check corrosivity with AWPA Standard E12-94. Design value factors should be per ICC-ES report/recommendations. Use appropriate design value adjustments if high moisture conditions. Some product do not allow ripping or planning.
 
I think as long as you're wood isn't exposed to moisture and is installed with a MC <19%, corrosion shouldn't be a huge concern. I would still look at SS or HDG fasteners (contact a Simpson rep, they've been helpful to me in the past), but the moisture is what initiates the chemical reaction. Similar to dis-similar metals - as long as there is no water, there is no galvanic corrosion.
 
Lion06...it is not a galvanic action issue...it is purely chemical. The level of moisture dictates the speed of the reaction, but corrosion can occur in such materials at less than 19% moisture.

It is often not the moisture content of the wood that is at issue, but the ambient humidity that causes a surface reaction.
 
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