Plywood grades

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Plywood grades

Postby Arne » Fri Apr 07, 2006 3:08 pm

I stopped at home depot to do some investigation.... I found 4x8x3/4 from $25.00 to $40.00 per sheet..... Some was rougher than others, but I found the lower priced stuff looked pretty good. I did a search on plywood grading, and got some information.

But, for a tear, does it really make a difference what type is used.? I will be undercoating the bottom and theoretically, the inside will never get soaked.

They all seem to be 5 ply (if I remember correctly).... I'm not trying to cheap-out, but don't want to spend money I don't have to..... any input would be helpful..
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Postby goldcoop » Fri Apr 07, 2006 3:22 pm

Arne-

First off was it 3/4" or 23/32"? :lol:

Is this just for floor?

What was it's designation? CDX?

That seems to be the most popular sheathing grade at big boxes...

CDX= C grade face, D grade back, X for Exterior use...

The face will probably have the voids/knots patched with "football" patches, the back will not be patched.

I would think face up and back down and undercoat it would be fine.

The only problem I can think of would be if you want to put vinyl flooring/peel -n- stick tiles, etc. might require a smoother underlayment to keep defects in the ply from "telegraphing" thru the flooring...

Check for excessive voids, look for a made in US stamp, check the plies to make sure they are tightly glued, no delamination...

JMO...

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Postby Arne » Fri Apr 07, 2006 3:58 pm

Well, the sign said 3/4 and I think the stamp on the wood did also.... the part that puzzled me was the cheap stuff actually had a decent surface on the top... there were, I think, 4 different grades, includin the vaneered for 40... not exactly cabinet grade, but nice looking.

I do not think the cheap stuff was cdx, but not sure that is real necessary in this application.... which partly was why I posted the question. Just seems like humidity should not bother most glue, and as long as it doesn't get soaked, I think the cheap stuff should be ok.... I'll need 3 sheets, so it isn't a major savings, but a savings, none the less.
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Postby Guy » Fri Apr 07, 2006 4:02 pm

Plywood grades are (in best to worst) - A, B, C,D for face (front) grades & 1, 2, 3, 4 for back grades. The lower the letter or number the better the material will be. All of our plywood is graded to the standards of the Hardwood Plywood & Veneer Association

A1, A2, B1, B2 is generally considered to be a good two sided product where both sides may be seen. Some blemishes are generally allowed on back side.

A3, B3, C3 are intended for use where one side will predominantly be seen but the other side needs to be reasonably clean, the back of items in this grade are generally good material but may have staining, less that acceptable veneer splices, scratches or other blemishes. This material works well for use as shelves, drawer sides & end panels

A4, B4, C4 are considered to be a good one side product where the back side will not be seen or it does not matter what is looks like. In A4, B4 or C4 the back of the piece may have open knots, filled knots, bad veneer seems or be of a different species that the front. This material will work well for drawer bottoms, covering of cabinet faces, bar backs & end panels.

CD is basically not to be seen.


Sorry, COOP
CDX is a softwood plywood and often improperly thought of as meaning exterior. That is not the case. "CDX Consists of a water-resistant bond and are designed for applications where long delays may be expected prior to providing protection, or where high moisture conditions may be encountered in service."
The real problems with lower grades of plywood are that they are not dimensionally stable. The thickness is not even and the veneer on the face is very thin And the lower the grade the less you can adjust this by sanding.

Here are links to more fully explain the differences and help you decide based upon your needs, and finances.

For Hardwood designations see:

http://justwoodworking.com/charts/hardwood_plywood.php

For Softwoods see:
http://www.awi-wa.com/_hidden/apagrades.htm
Regards,

Guy
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Postby Mitheral » Fri Apr 07, 2006 4:31 pm

arnereil wrote:Well, the sign said 3/4 and I think the stamp on the wood did also....


the 3/4 is nominal now a days. You won't notice the difference unless you try to set it into a 3/4" dado.
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Postby goldcoop » Fri Apr 07, 2006 4:31 pm

Guy wrote:CD is basically not to be seen. Sorry, COOP
CDX is a softwood plywood and often improperly thought of as meaning exterior. That is not the case. "CDX Consists of a water-resistant bond and are designed for applications where long delays may be expected prior to providing protection, or where high moisture conditions may be encountered in service."

Guy-

No apologies necessary...:bowdown:

Just thinking of what's most likely encountered in the big boxes...

Soooo what ya think about CDX in Arnes' application?

I think it should be fine if applied as described and probably the cheapest too!

Depending on deck framing 23/32, 3/4, 25/32 sounds kinda thick & heavy?

Cheers,

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Postby Arne » Fri Apr 07, 2006 5:14 pm

bingo on the weight... they had some 2x2' squares of 1/2 and 3/4.... and I put them so I could deflect them by stepping in the middle.... the 1/2 was like mush and would require too much support from the bottom.... they do have 5/8 and I'll look at that... right now, the design gains 60# by using 3/4 instead of 1/2, but that might be easier than figuring out all the supports needed for 1/2 (and the attendant weight of those supports).
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Postby goldcoop » Fri Apr 07, 2006 5:55 pm

arnereil wrote:bingo on the weight...


Arne-

Like I was worried about weight with my build?! :lol:

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Postby Arne » Fri Apr 07, 2006 10:10 pm

My current tear weighs 1,200 pounds. a couple of reasons to justify building my second one: 1) better layout; 2) more aerodynamic; 3) lower weight...

2 & 3 are to keep my gas mileage up, 1 is to correct some deficiencies from my quick-build on #1..... so I have spent hours trying to figure out how to use 1/2" for the floor, but after doing my 'step-on test' at h/d today, I don't think it is worth it... but as mentioned, the 3/4 will add 60#'s I'd rather not have.

There will be savings over the conventiional 1800# trailer frame (I'm reconfiguring the h/f frame to a long V shape), but I was just looking for more.... I have a feeling I can't save much in the rest of the trailer......

Bob Villa says (and it seems true) that you can roughly figure each 1/4" of ply weighs 25#..... I'm going to try using 1/8" instead of 1/4" in some places, and 1/4 instead of 1/2 in others..... still think it will come in at 1,000 pounds with all the goodies, like a/c, microwave, mattress, TV, etc.....
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Postby Micro469 » Fri Apr 07, 2006 10:24 pm

Do you want to expand on that "step test"? If you just raised the ply on two sides, then yes it's going to bend. But if you frame it around four sides, and support in equal distances in the middle, you'll find it doesn't bend as much as you may think. If you use it for the floor, you're still going to have to put supports crossways no matter what the thickness of ply.
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Postby Arne » Fri Apr 07, 2006 10:56 pm

Yes, it was only supported on 2 opposing sides... you make an interesting point.
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Postby goldcoop » Sat Apr 08, 2006 8:56 am

Arne-

OK!

Enough talk about plywood!

Who's the arm candy in your avatar?

I know it ain't Shirley!

Cheers,

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Postby Arne » Sat Apr 08, 2006 9:09 am

Coop, Siobhan is an Irish step dancer we know..... She is from Listowel, County Kerry, Ireland... Shirl and I love Ireland and try to visit often. I won't tell Shirley what you said.. She might not like the implication./g/

About plywood, I think I've got enough information..... I really don't want to use 3/4, but for safety sake, I don't want to under build with 1/2 and have problems down the road (so to speak).... I can look at 5/8, but the weight/$$ savings is hardly worth it....

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Last edited by Arne on Sat Apr 08, 2006 9:25 am, edited 2 times in total.
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Postby goldcoop » Sat Apr 08, 2006 9:16 am

arnereil wrote: I won't tell Shirley what you said.. She might not like the implication./g/


Arne-

NOTHING implied! Honest!

Just know it wasn't Shirley...

I used 3/4" for my deck floor and retrospect think it was to heavy; but I had a pretty robust framing...

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Postby Arne » Sat Apr 08, 2006 9:29 am

Coop, what was the widest unsupported span you had?

I think I could do 24" with 5/8, but think with 1/2 it would have to be less than 24". That means a lot of supports underneath, and I'd like to do 24" from front to back with nothing across the 5' width... I just don't think 1/2 would handle it, though 5/8 might with a stringer down the middle....

If I have to add a lot of support underneath, it adds complexity to the build, weight and a bit of $$.....
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