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CDX Ply; Which is the good side?

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http://boards.diynetwork.com/eve/forums/a/tpc/f/9221916776/m/9823991277

Jul 13, 2013, 11:22 PM
SturdyNail
CDX Ply; Which is the good side?
This may be a silly question, but I bought CDX ply for re-sheathing one of my exterior walls. I can't tell which is the better (C) side. The side that is smoothest to the touch also has larger, but fewer, knots than the other side.
There is printing on the plywood. Could that be an indicator? Do lumber mills generally print on the good side or the "bad" side?

Thanks.
Jul 13, 2013, 11:32 PM
Jaybee
The smoother side is the 'C' side. Usually the 'D' side not only has knot holes but also more splits in the topmost layer.

Here's the thing though - CDX is a form making plywood and is really not suitable for exterior sheathing. Sure, you could hang it up there but just the fact that you can't tell which side is which should tell you something. Over time you will likely experience some delamination or bubbling of the top surface on the 'C' side.

Now, if you are using the CDX as a sheathing that will then be covered by something else - siding, shingles etc, then it will work fine. And, it will not matter at all if the 'C' side or the 'D' side is facing out as it will be covered.

Have you considered something affordable and easy to install like T1-11, or are you trying to match up to other parts of the house?


Jaybee
Jul 14, 2013, 12:57 AM
SturdyNail
Thanks JayBee,

The CDX will be covered with house wrap and then the cedar shingles (at least until I can afford to replace the cedar with Hardie).

The CDX is replacing the junk sheathing that was on the house (Graylight/glorified Homasote), so I'm really only matching thickness of material.

I've seen T1-11 used on sheds, but hadn't considered it for my current project.

SturdyNail
Jul 14, 2013, 02:17 AM
Jaybee
It will work fine for that use of it. CDX has more of a tendency to bow compared to other plywoods because it has less number of layers - but those layers are made of thicker material. If it is securly fastened to your studs 16" OC then it will be fine.


Jaybee