Re: [GBlist] OSB

[BillArchtx@aol.com]

Alan - 

OSB, and virtually all composite materials - plywood too - are manufactured 
with waterproof resins and adhesives.  The problem is that there isn't 100 % 
saturation and encapsulation of the fibers, so if continually exposed to 
moisture - or as Joe Ltsebruck says," If the rate of wetting exceeds the rate 
of drying," then the cellulose fibers will become food for bacteria and we 
have "mush" - the first stage of rot.

Provided the material is allowed to dry well between wettings - as is the 
case on most construction sites, many months of weathering will safely be 
endured.

OSB comes in structural grades equal in performance to plywood of the same 
thickness - such as "Structural 1."  The CDX label tells us: one side is "C" 
grade veneer, the other side "D" grade veneer and the "x" is for exterior 
glue.  With lower grade interior veneers that have open knot holes, splits, 
checks and other voids, the problem is that water gets into those spaces to 
cause rot or freezes and causes the veneers to separate.

Best,
Bill



Bill Chaleff, R.A.

Chaleff & Rogers, Architects
1514 Montauk Highway  P.O.Box 990
Water Mill, NY   11976

phone: 631-726-4477
    fax: 631-726-4478

BillArchtx@aol.com

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