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Re: mold growth on joists

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The AITC Timber Construction Manual has some information on mold and decay. Typically, if there are actual mushrooms growing on the joists, their strength has been effected. How much, there's no way to know unless samlples are taken and tested. 

I generally require replacement of any joist that has actual mushroomy stuff growing on it. If there's just a haze of mildew/mold, and it can be removed by scraping with a stiff brush, plastic card, or whatever, that the joists are probably ok. 

Once the moisture level in the wood is reduced below about 15%-19%, the mold/mildew/decay stops growing and thus stops degrading the wood fibers. Similar to combustion, there are several factors required for mold growth. Moisture, food (the wood), favorable temperature and air. Remove any one, and the decay stops growing. The moisture is the "easiest" to remove. Of course it may require conditioning the space, improving drainage, ventilating, etc..but its easier than removing the air. 

Mike Perakis, P.E.

>>> Peieng5590(--nospam--at)aol.com 03/15/02 07:39AM >>>
Any words of wisdom as to the damaged caused by the growth of mold on wood joists, and by mold I mean mushrooms and hairy looking stuff and filmy looking stuff.  Some joists have obvious degradation noted by shoving a awl in and through the joists, the problem is: after the moisture  and ventilation is fixed, what do we do with the joists that are still hard, seemily undamaged, can we leave the stuff adhered to the side of the joists?

Jeff Fertich, P.E.
Gettysburg PA

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