What type of plywood is this?

[Matt Allan]

Took up some vinyl to lay down some type and have to replace a few pieces of the plywood that are damaged. I need to make sure my top layer of subfloor plywood is exterior grade though. I couldn't get a good look until I ripped part of the damaged piece out, I now see the factory edges are im guessing sealed. (see picture)

Just wondering if anyone out there can tell me if this is exterior grade or not? Like an idiot I thought it was all interior plywood, because I know the bottom layer is because I can see from the basement it is stamped interior so I was just going at the top layer thinking I had to remove it all. If this turns out to be exterior I could have just made a few small patches.

Any help is greatly appreciated.

Thanks

[jack duren]

from what i can tell its fir plywood. easily found in the 70's through early 80's. speacial order these days.

used on flooring and carcasses for cabinetry. the good ol days....jack

[Mark Singer]

Cdx ...Roof or floor sheathing

[Matt Allan]

Cdx ...Roof or floor sheathing

I am guessing that would make it exterior grade? Just need to make sure before I leave the rest down so I can tile over it. Tiling over interior is not advised.





Thanks

[Steve Cox]

Almost all exterior plywood has black glue lines, almost no interior grade does. Look at the edges, if there is a black line between the layers, exterior.

[aurelio alarcon]

Looks like CDX. Exterior grade. Just what Mark says. Its for roofing and flooring.

[Bill Neely]

CDX. I worked at a ply mill in Albany, OR, this place made higher grade ply and didn't do CDX (which at the time was the only ply that could be laid up by machine). We did make some siding: T-1-11, etc. The interesting thing was that although we also made interior grade ply, we used exterior glue/resin for everything. The reason was that it took so long to clean and change a spreader from one to another that it was cheaper to run the more expensive exterior glue. I'm fairly certain that this was common practice in all but the very biggest mills.

[Matt Allan]

Thanks for the replies. I am going to assume its exterior. Stuff is beyond a pain to rip out and hard to not mess up the layer under it when trying to pry it up.

Thanks for the help.

[Matt Allan]

Bah, right when I post this and feel ok about leaving it down I read I should not use CDX for tile. I guess D has too many voids and in general is not recommended. Sigh. Back to the prybar, I can't catch a break.

[Donnie Raines]

For what it is worth: I used the existing CDX in my home and tiled right over it.....that was a year ago and we walk(jump, run, the kids ride their big wheel etc....) throughout the day. Not one issue to this date.

If memory serves me, it depends on the type of adhesive/mastic you are useing. Read the labels and see if this is the case.

[Matt Allan]

Well it is really a friends floor, but I am helping him repair a few places on the floor before he does the tile job. Neither of us had any idea about the plywood being interior/exterior so I figured you guys here would be able to tell.

I cannot imagine this stuff not being good enough for a subfloor. A layer of 5/8th plywood under this layer of 5/8th CDX. Ripping this stuff up is one of the hardest things I have ever done and it seems rather solid to me. He is also going to put down a layer of cement board screwed into the plywood layers with thinset under it as well. Few of the pieces of cdx plywood are getting replaced with AC. Couple stops had some damage.

If it was my floor, I would just go ahead but I would feel even worse if I gave him that advice and then had a problem down the line. I sure don't want him or his wife hunting me down if he had problems :)

[Chris Padilla]

Matt,

The size of the tile dictates how much deflection in the floor it can handle. As you can imagine, the large the tile, the less floor bounce it can handle before cracking. The tiles should have some sort of deflection rating on them or on the box.

Mastics tend to be a pain to work with and thinsets tend to be easier...for the beginner. Be sure to add latex liquid to the grout to keep it flexible.