Underlayment for glue down LVP/LVT

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New Member
Jan 7, 2023
Will 15/32" A-C plywood sheathing suffice as underlayment for glue down LVP/LVT or are there going to be too many hollow cores in it for LVP/LVT? I need to build up the floor by about 1/2" before putting the finished floor down, or otherwise I'd just use 1/4" SurePly. I could use 3/8" CDX with a layer of SurePly on top of that, if I have to, but just trying to save some time and $$$.
Sounds like you already know the answer. If you want to use an inferior grade plywood for underlayment it also sounds like you already know the risks.... If you're asking me I'd just do it right the first time, go with the SurePly.
If I spent 45 minutes and used a $35 bag of filler to repair a couple of voids or defects in a master bathroom that had 4 sheets of plywood....... Add my $75 or more to the cheaper grade of plywood and see how that compares to buy an AC or CCPTS.
Sheathing has structural properties, and not something you'd want for finished surfaces.
If you buy the better quality material, you will sleep better. As far as prep work, it will save you time also. AC and CCPTS will give you a better, smoother surface with much less prep work.
Thanks for the advice and info. I'll go ahead and put down a layer of 11/32" CDX on top of the existing 23/32" plywood subfloor, and then 1/4" SurePly underlayment on top of that. That'll give me a total thickness of 1-5/16" before the glue down LVP gets installed.

What length of staples should I use for the 1/4" SurePly, and should they be divergent or standard type?
I like the chisel points and they have to be at least 5/8 of an inch for 1/4" ply but not so long as to go all the way through the plywood you're nailing in to. Since you will have two layers of plywood underneath I think 1" would work for you.

But it seems to me if you could find yourself some 1/2" underlayment grade plywood that would save yourself the time of installing the two layers. That you're better off screwing down.
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Is there something in specific (brand/tradename) that you could point me to that is 1/2" and suitable for underlayment? I'm familiar only with the sheathing and subfloor type plywood that can be found at the big box stores. I'm sure this type of plywood would be something I'd have to special order.
You can use AC exterior grade plywood. Which is what you originally mentioned.... I just read the sheathing part which generally refers to a lower grade of plywood which is not what you want. Sorry about that.

Just be sure to put the smooth side up. It's been a while since I bought any but used to be readily available at the lumber yard.
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