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Unread 04-24-2007, 09:13 PM   #56
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Join Date: Mar 2007
Posts: 102
Moderators - Could someone post this in the sub-floor thread in the library? I received the following response from APA regarding my question on PRP-108 rated plywood and it's uses as a viable underlayment. The basic jist is that since PRP-108 rating do NOT carry a veneer face rating, it can be considered a D-D grade as seen on PS-1 rated plywood. This information was difficult to obtain and while this may be known by some of the seasoned installers, based on this information below, PRP-108 or PS-2 rated plywood should not be used as a tile underlayment as this is similar to D-D rated PS-1 plywood.


The following is in response to your inquiry regarding Performance Rated APA Rated Sheathing plywood as compared to "CCX" APA Rated Sheathing.

Plywood APA Rated Sheathing panels may be manufactured under the provisions of PS 1-95, PRP-108 or PS 2-04 (previously PS 2-92).

Voluntary Product Standard PS 1-95 for Construction and Industrial Plywood provides detailed manufacturing specifications and performance testing provisions for several plywood grades including C-C Exterior, Rated Sheathing (commonly referred to as CCX).

Other APA Rated Sheathing panels, plywood and OSB, are manufactured under the provisions of APA PRP-108, Performance Standards and Qualification Policies for Structural-Use Panels, or under Voluntary Product Standard PS 2-04, Performance Standard for Wood-Based Structural-Use Panels. These standards establish performance criteria for specific designated construction applications. The ICC Evaluation Service and HUD recognize APA PRP-108 Performance Standards.

PRP-108, PS-1 and/or the PS-2 grade conformance where applicable are given in the lower portion of the APA trademark.

APA PS-1 plywood sheathing panel grades are often identified in terms of the veneer grade used on the face and back of the panel. PS-1 plywood APA Rated Sheathing panels are generally graded C-D Exposure 1 or C-C Exterior.

PRP-108 and/or PS-2 APA Rated Sheathing panels, OSB AND plywood DO NOT carry a veneer grade designation. However, PRP-108 and/or PS-2 plywood may be equivalent to a D-D grade although there is no actual D-D grade.

Use and application recommendations for APA Rated Sheathing are the same regardless of panel composition or the standard to which they are produced.

I hope this information will be of assistance to you. If we can supply you with any further information, please let us know.

Merritt Kline
Product Support Specialist
Wood Products Support Help Desk
APA-The Engineered Wood Association
Southern Forest Products Association
Structural Insulated Panel Association

Mike - JerseyReef
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