The New Commercial Standard For Douglas Fir Plywood

Higher performance standards for adhesives used in all interior type Douglas fir plywood top the list of product refinements set forth in the new U. S. Commercial Standard CS45-47 adopted by the Pacific Northwest panel makers rvho produce two-thirds of the nation's plywood.

Other improvements of quality under the standard, promulgated through the National Bureau of Standards and effective for new production from September 15, include:

1. Higher specifications for inner plys of all grades of both exterior and interior types of Douglas fir plywood.

2. An improved Plyscord sheathing grade. 3. Simplification of grades through combining the old Plywall (wallboard) grade and Plypanel Sound 1 Side grade. Plypanel Sound 1 Side grade now becomes the all-purpose interior panel material.

"That which was special now has become regular," Managing Director Charles E. Devlin of Douglas Fir Plywood Association of Tacoma, Wash., commented in explaining the rigid new perforfilance requirement for adhesives in interior type fir plywood. "The highly moisture resistant (but not waterproof) adhesives previously used only in 'special' or 'premium' quality interior fir plyr,vood, under the nerv standard is the regular glue for interior type Douglas fir plywood."

Performance Upped

These previously-considered "special" adhesives originally were introduced in tl-re Plyform (concrete form) grade fir plywood nine years ago to assure a panel for form construction that can be used numerous times on concrete jobs, the plywood official said. This type of adhesive recently has been termed "10 cycle glue," "concrete forrn glue," and "CCF glue" as u'ell as "special" or "prenrinrn."

Formerly, the test for regular interior plywood was two cvcles of rvetting and drying rn''ithout delamination. As set forth in the new Commercial Standard, all interior type fir plywood now is produced to withstand an average of 10 cycles of wetting and drying rvithout failure.

There are just two types of Douglas fir plyrvood, the type being determined by the glue us€cl to bond the plys together. Exterior type fir plywood is manufactured with completely water-proof adhesives and is intended for permanent outdoor and marine uses; interior type fir plywood is bonded rvith highly moisture-resistant (but not water- proof) glues and intended for inside uses and such structural parts of the house as sheathing and sub-flooring.

Within each type there are several appearance grades, the grade being established ,by the appearance properties of the wood in the outer or face plys rather than with regard to the adhesive.

Limitations Set

The raising of the quality standards for all Douglas fir plyrvood is exemplified in stricter limitation of defects permitted in inner plys of the exterior type material under CS45-47. This tightening of the inner veneer construction is to assure greater serviceability; quality of outer plys is, of course, determinecl by appearance requirements for the various grades.

Limitations, although less stringent, also are announced for the veneer of inner plys of interior type panels.

Also, under the new standard, certain other western softu'ood species are allo'ived for inner plys of several grades of interior type plywood, but Plyscord (sheathing grade) and Plyforrn must be entirely of Douglas fir. Similarly, all inside as well as outer plys of the exterior type fir plywood must be of Douglas fir veneer.

The new, more stringent specification for glue performance in interior plywood is particularly important in the Plyscord grade as such panels may be subjected to wetting from rain during construction. As well, the veneer specifications for outer plys oi this grade of material have been modified to provide a structurally stronger panel. Plyscord remains, however, a rough, unsanded material for utility use where appearance is of little consequence.

Grades Combined

In effect, the old Plywall grade, rvhich has proved highly popular for interior u'all covering and for miscellaneous uses where only one paintable surface is desired, is being replaced by the new Plypanel Sound 1 Side (SO1S) grade. The face of the Sound 1 Side panel is, and has been, the same as that of the old Plyrvall. In the back of the panel being retained, blemishes and appearance defects permitted must be smaller than those previously allorved in the old Plywall back, but may be somervhat more conspicuotts than in the back of the Plypanel SO1S grade nnder the previous standard.

(Continued on Page 17)

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