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Exterior finish at top of PWF basement?

The "Permanant Wood Foundations Design and Construction Guide" by the Southern Forest Products Association,shows and discusses a treated plywood "protection strip" at the top of the underground portion of a PWF basement. It's, discussed purpose is to protect the poly damp proofing material from UV and other hazards. I would like to carry my thin brick to below grade. I propose replacing the treated plywood with a layer of 30# felt, stainless mesh (lath) and cement plaster to which the thin brick is attached with "thin set". Are there problems or "issues" with this?

Asked by Jerry Liebler
Posted Tue, 07/01/2014 - 12:31

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4 Answers

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1.
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Jerry,
I'm not an expert on wood foundations, but your suggestion makes me nervous. Are you installing adhered thin brick on your entire wall, or just in a thin band near the soil to disguise your plywood foundation?

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/01/2014 - 13:34

2.
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Martin,
My entire exterior will be "thin brick". The portion above the PWF basement is installed on "Ambrico EZ wall" a steel substrate system. At the base of the portion on the EZ wall panels is a "weep flashing" and an expansion joint where the PWF begins. Since EZ wall is not recommended below grade I'm transitioning to the more labor intense "lath and plaster" method of of attaching adhered masonry that is approved for below grade use..

Answered by Jerry Liebler
Posted Tue, 07/01/2014 - 14:45

3.
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Jerry,
Aesthetically, it seems disturbing (to me) when siding disappears below grade. This is a judgment, and other people's judgments will probably differ.

I think it's preferable to have a clear separation between the siding on the above-grade walls (in your case, thin brick) and the visible part of the foundation (usually poured concrete, but in your case, pressure-treated plywood, or something else).

Your method raises water penetration issues. But perhaps the crushed stone and foundation drainage that accompanies your all-wood foundation handles these issues.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/01/2014 - 15:01

4.
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The house I'm currently living in has a conventional brick exterior and it continues well below grade, all the way to the footings in fact. IMO brick siding is normally continued below grade and to do otherwise would lookout of place.

Answered by Jerry Liebler
Posted Tue, 07/01/2014 - 15:18

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