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woodnewbie
01-28-2003, 04:11 PM
I don't see where this question was posted before, so forgive me if it turns out it is redundant.

In another discussion, I had a "conversation" about "shop grade" plywood, I've seen posts and materials lists that call for "cabinet grade" plywood, and I've seen "paint grade" plywood at home depot. Add to that A/B B/C grading which I kind of understand, and I am somewhat baffled.

I've searched the internet to get a breakdown - best to worst/worst to best listing so I can tell if paint grade is better or worse that shop grade (I suspect worse), and cabinet grade, I think is like A on one side C on the other???

Is there a listing here, or can you tell me how they stack up compared to one another?

woodchuck1954
01-28-2003, 04:41 PM
A is the top grade, it has no knots, plugs or any other defects. It is also the best grade for exterior. B grade is paint grade. It has
small tight knots, no or few plugs. Both A and B outer plies come sanded. Now the difference between interior and exterior, is NOT only the type of glue they use, but ALSO what grade the interior plies are. NO exterior grade plywood can have anything below C gradeinner plies,with exterior glue, if exposed to the elements. Plywood grades look like this- ext.- ABX,ACX,BCX,CCX,CDX-int.-AB,AC,BD,CD. Paint Grade could be CCX, plugged and sanded. Shop Grade can be ANY grade of plywood. It has minor defects during manufacturing. There is a special stamp for shop grade. Shop Grade is illeagal to use on any structure, technically. If you shop around, sometimes you can find a high grade of plywood, as shop grade, that is say ACX, with few or small defects, at a very reasonable price. When building with shop grade, normally you can maneuver AROUND the defects. Plywood is graded for BOTH faces and inner plies. You also must choose either one or two good faces.

woodnewbie
01-28-2003, 05:05 PM
Thanks, then if paint grade is B grade, it is probably better than cabinet grade?

Burt
01-28-2003, 06:50 PM
There is another curve ball to throw in here. It depends on whether you are talking "construction" or "cabinet" plywood. Construction grade uses the AB, AC, BC, etc grading. In construction, the first letter is the face and the second is the back. A is the best. In cabinet plywood, the grade is a letter plus a number. Example B2, c3. A is the best face and 1 is the best back. The terms "cabinet grade" and "paint grade" are often used as a non-specific term to identify two catagories. In these terms, cabinet grade usually translates to a stain grade and paint grade is for a lesser grade. The surface is good but not as nice to stain.

Danford C Jennings
01-29-2003, 10:07 AM
Actually, The American Plywood Association established the "standards" for plywood grading, exterior and interior plywoods are two different animals. A sheet of A-A interior grade is not suitable for exterior use....

Veneer Descriptions

N - Special order "natural finish" veneer. Select all heartwood or all sapwood. Free from open defects, allows for some repairs.

A - Smooth and paintable. Neatly made repairs are permissible. Also used for natural finish in less demanding applications.

B - Solid surface veneer. Circular repair plugs and tight knots permitted. Can be painted.

C - Minimum veneer permitted in Exterior type plywood. Knotholes to 1", limited splits permitted.

C plugged - Improved C veneer with splits limited to 1/8" in width and knotholes and borer holes limited to 1/4" x 1/2".

D - Used only in Interior type plywood for inner plies and backs. Permits knots and knotholes to 2 1/2" maximum. Limited splits are permitted.

Softwood Plywood Grades For Interior Use

A-A - Cabinet doors, built-ins, furniture where both sides will show.

A-B - Alternative to A-A. Face can be finished natural, back is solid and smooth.

A-D - Face can be finished natural used for paneling, built-ins, and backing.

B-D - Utility (shop) grade. Face is paintable. For backing, cabinet sides, etc.

Hardwood Plywood Grades

Custom Grade (1) - Has no defects; veneers may be made from more than one piece, but must be carefully color and grain matched.

Good Grade (2) - Similar to Custom Grade with the exception than the face veneers need not be as carefully matched.

Sound Grade (3) - Suitable for painting, but not for natural finishes.

Utility Grade (4) - Allows knot holes up to 3/4" in diameter, discoloration and minor openings between joints.

Backing Grade (5) - Permits knot holes up to 2" in diameter, splits up to 1" wide, and other defects that do not affect the strength of the panel.

In the hardwood plywood gradings the above may apply to both sides.

All plywood must be stamped, if the stamp is illegible, don't buy it. The box stores are notorious for selling lower grade ply at higher grade prices....FWIW.

Dano

Source: American Plywood Association

dmiller
01-29-2003, 11:38 AM
Thanks Dano. That one got printed and posted in the shop.DAVID

woodnewbie
01-29-2003, 12:22 PM
Thanks Dano:

That is EXACTLY what I was looking for. As Dmiller said, this one gets posted in the shop.

That also helped my find the following:

http://www.apawood.org/pdfs/managed/X505-R.pdf

which is a 32 page document that's pretty exhaustive. It does not talk about "paint grade" or "cabinet grade" that I saw, but does mention that "shop" grade failed to meet the specifications that it was supposed to meet. I take that to mean that it could have been otherwise speced at any other level, but then they found a defect that made them change their mind - so the "other markings" are to be disregarded.