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Re: Historic Wood Structures, DECAY

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Thor,

        I recently worked on the restoration of wood frame building that had
been left exposed to the elements for a similar length of time.  We had very
little problem from decay resulting from the exposure (although we did have
decay from other causes) but we did have one other serious problem.  Once the
structure was fully enclosed and it began to dry out many of the wood components
began to split.

        The building components were all Douglas Fir.  The floor joists were
2x10; the beams were multiple layers of 2x10 and 2x12; the columns were solid
members from 6x6 to 12x12 as required.  About 20% of the floor joists developed
severe enough splits to become ineffective os they were "doubled" or replaced.
A smaller percentage of columns developed splits which we repaired.

        I would expect oak to be less susceptible to this problem than Douglas
Fir; never-the-less I would be on the look-out for the problem.  I would try not
to dry it out too fast.

Regards,

H. Daryl Richardson

"Thor Matteson, SE" wrote:

> I scanned most of the replies regarding the 85-year-old oak framing that was
> left exposed to the elements for three or four years, but found little
> specific reference to what would be my biggest concern:   Decay.
>
> A recent (last 24 months?) article in the ICBO "Building Standards" magazine
> outlined the "pick test" for wood.  It used Douglas Fir as an example, may
> not completely apply to oak.  To perform this simple test, you will need an
> awl or other pointy object.  Poke the awl into the area of wood you want to
> test, about 1/8 inch deep, and then pry up some of the wood fibers.  If you
> hear a pronounced splintering sound and pry up some long strands (one or two
> inches long) of wood fibers there is probably not enough decay to worry
> about.   If your awl just pops out some short chunks of wood less than 1/2
> inch long, and/or if the pried-up wood breaks right over the awl, you have
> decay.
>
> THE  SCARY  PART  is how much strength the wood has lost if your test
> indicates decay.   Something like 70 percent of the wood's "resilience" (I'm
> pretty sure that that was the term they used--would have been much more
> helpful to say "bending strength",  "stiffness", etc.) can be lost by the
> time you can detect decay with this test!   The article recommended
> replacing certain members (such as balcony supports) if the pick test
> indicated any decay at all. Another article I read long ago stated that up
> to half of the wood's strength can be lost at the point when a trained
> specialist can just begin to detect decay under a microscope....
>
> Good luck!
>
> Thor
>
> www.shearwalls.com
>
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