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Thread: Modern version of this plywood?

  1. #1
    DIY Member ironspider's Avatar
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    Default Modern version of this plywood?

    Hello all, we are remodeling our kitchen (1963 ranch) and have torn out a dividing wall that seperated the old kitchen from the living room/dining room. The living room/dining room had carpet on the floor which we have ripped up. The plywood underneath it looks great. Now, in the kitchen, the previous owner had some hardwood (distressed very "boat/nautical-deck-style planks) which we pulled up. Under that we see a vinyl tile which is sitting on top of a 1/4" piece of plywood which is sitting on top of some other kind of tile which is sitting on top of a 5/8" piece of plywood. This 5/8" piece of plywood is the same height as the living room/dining room piece of plywood. Underneath the 5/8" piece of plywood is a 1/2" piece of plywood. Wow, that's a lot a fossil record or something!

    So our plan is to prepare our kitchen floor so that we can use bamboo or hardwood to cover the new, larger, open space of all three areas. So we are cutting out all the tile and the 5/8" plywood in the kitchen (it would just be impossible to try and get these tiles up and who even knows what that tile attached directly to the 5/8" plywood is!) and then planning on putting new 5/8" plywood on top of the existing 1/2" plywood so that all three areas match up in "subfloor" height.

    So I was cutting some of it out today and saw a green paint symbol under neat the 5/8" plywood (see attachment). I do not *think* this is tongue and groove plywood but I could be wrong? I guess I'll have to pay more attention and cut up a piece where I can investigate that. But when I go to get some new 5/8" plywood (we'll need about 5 sheets) I want to make sure I get the correct thing. So can anyone help me decipher this green symbol so that i don't get overwhelmed trying to explain what I need at the local lumber yard?

    Lastly, for attaching the new plywood, it appears that this plywood is just atached to the floor joists using 2.5" ring shank nails--there is no construction adhesive anywhere. (The floors don't squeak or anything when I walk on the 1/2" plywood remaining there so maybe that is glued down?). Is this the preferred way to do this? Or are there more modern ways of attaching this down or better methods?

    Thanks in advance!

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  2. #2
    DIY Senior Member kcodyjr's Avatar
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    I see "A-D" meaning one side good one side sucks, and "INT" meaning interior. "DFP" probably means douglas fir plywood.

    If you're down to the joists, that would be the structural subfloor. Did you have to cut it where it meets the walls, or were the edges accessible?

    Look out for support at the edges of the sheets. They should be lying joist to joist on one axis, but on the other, either it should be tongue-and-groove, or there should be blockers present between the joists to screw/nail the edges down.

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    DIY Member ironspider's Avatar
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    Quote Originally Posted by kcodyjr View Post
    I see "A-D" meaning one side good one side sucks, and "INT" meaning interior. "DFP" probably means douglas fir plywood.

    If you're down to the joists, that would be the structural subfloor. Did you have to cut it where it meets the walls, or were the edges accessible?

    Look out for support at the edges of the sheets. They should be lying joist to joist on one axis, but on the other, either it should be tongue-and-groove, or there should be blockers present between the joists to screw/nail the edges down.
    I'm not down to the studs yet as there is 1/2" plywood still below this 5/8" that I'm cutting up. So would that 1/2" be the "structural subfloor"?

    I'm not done pulling up the 5/8" yet (about 50% cut up and removed in the center of the room) so I haven't reached the edges, but it appears to just be plywood sitting on top of the 1/2" plywood and just railed into the joists with the 2.5" ring shank nails.

    I guess, at this point, I should probably be asking if the 5/8" I'm going to have to put down to replace the 5/8" I'm cutting up should be T&G? Or just regular sheets of plywood?

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    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by ironspider View Post
    I guess, at this point, I should probably be asking if the 5/8" I'm going to have to put down to replace the 5/8" I'm cutting up should be T&G? Or just regular sheets of plywood?
    I am thinking you might also be asking how to avoid squeaks when you rebuild your floor.

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    DIY Member ironspider's Avatar
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    Right Reach4, that's what I was going for in the original post asking if there was a smarter way to do the replacement of the 5/8" plywood to improve it (as it didn't squeak before and was only down with nails).

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If all of the joists are good quality, straight, and the resulting plywood can lay flat when it was installed, then if well fastened, if the edges are blocked or it is T&G, it may not squeak. But, construction adhesive on the joists bonds things together better, improves deflection ratings by sharing the load and can help hold the floor flatter. BTW, once the adhesive sets, the fasteners are mostly redundant - similar to the clamps when you glue wood together.

    If you're tearing it all out, I'd prefer to use nominal 3/4" T&G stuff (I like Advantech - it's about 10% stiffer than normal ply of the same thickness).
    Jim DeBruycker
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    DIY Senior Member kcodyjr's Avatar
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    Yeah, that last 1/2" between your foot and the joists is the subfloor. In addition to holding up the layers and people above it, part of its job is to hold the joists square. The two work together to become stronger than either.

    If that's solid, and neither deflects nor squeaks when you shake your weight on it, then I see no reason to pull it up, nor to worry about tongue-and-groove on the next layer. That 1/2" subfloor will hold it flat. How big are the joists holding it up? What's the joist span?

    That said, 1/2" is a bit weak for a subfloor. I'd be curious to know where the layers above it end. I'll put down a friendly $5 bet that all the BS above it stops at the wall, but the 5/8 as well as the 1/2 go below the walls. That would make it a two-layer subfloor, which is an improvement in strength over a single layer of the same thickness when the builder makes a point of not letting the seams line up.

    I'm not sure what the right thing to do is with adhesive between layers. I know you're supposed to use it on the joists before the 1st subfloor layer goes down, and I know you're supposed to put the thin-set mortar below cement board as well as above, so it does stand to reason there should be a skim layer of adhesive.

    If you *do* have a deflection problem, then I'd personally rather see it stripped down to the joists and repaired properly rather than trying to "reinforce from above."

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    Retired Defense Industry Engineer jadnashua's Avatar
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    You can laminate a second layer of ply to the first, but you can't really use an adhesive...it's very detail oriented...you must use a full-spread of wood glue, like Titebond II, or something similar, and you must get it all together before the glue skins over, but it does may the assembly stronger than two layers. Done right, it's good, but it is very easy to do it wrong, and all of the industry tests where two layers are required (say for using a natural stone tile), it is based on anchoring the second layer to the first. 1/2" is VERY hard to screw into, and may be just as good to treat it as if it weren't there, and screw the second layer into the joists, with some in the field to hold them together. If you do try to screw into 1/2", you may find you need to drill pilot holes and through holes to keep the screws from stripping out. Pilot hole all the way through both sheets, a through hole (use a drill stop) through the top layer, then you have a chance of not stripping the screw or jacking the top layer up off of the bottom layer. The pattern and spacing of the screws is important.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Moderator & Master Plumber hj's Avatar
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    I cannot imagine why they would use A/D plywood for a sub floor. Usually it is C/D since it is not going to be visible.
    Licensed residential and commercial plumber

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    DIY Senior Member kcodyjr's Avatar
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    Quote Originally Posted by hj View Post
    I cannot imagine why
    I'll take a stab at why. It's also serving as underlayment for the tile. "C" surface wouldn't be good enough for that.

    Also, let's remember it was done a long time ago, in a code revision far far away.

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you are going to tile this area, you do not want ANY 'D' faces in any of the layers...industry standards require all faces to be 'C' or better. Voids (i.e., D) equate to potential deflection on point loads, and is death to tile.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member ironspider's Avatar
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    Hey gang, I snapped a couple of pics to answer some questions posted in this thread. I don't know if any of this info changes anything but I thought I'd post em anyway!

    1. It appears that the 5/8" A-D plywood (the "good" side is facing down so that it is against the 1/2" subfloor) is not under the walls/wall framing (see attachment #1). I can see the edge of it all the way around the kitchen area and living room/dining room. So when I am done cutting it up, thee will be no 5/8" plywood anywhere in the kitchen zone. It is still in the living room and dining room, which is now one big open space with the kitchen (which is the original reason I need to replace the 5/8" plywood--to make the two areas equal height in preparation for some kind of flooring (bamboo/hardwood/TBD) to be laid over the entire thing.

    2. I don't *think* the 5/8" plywood is T&G because I haven't found any grooves or tongues in the 200sqft or so I've cut up so far. Also (pics 2 (8' edge) & 3 (4' edge) ) the seams between the 5/8" sheets just look like they stop flush against each other.

    3. The 1/2" subfloor is attached directly to the studs and I don't *think* that's T&G either. In pics #4 & #5 you can see it sitting on the joist and, in pic 5, that it's just nailed down to the joist with a small, but visible, gap between them.

    4. I thought I'd throw in a pic of the kitchen side of the flooring and why I am pulling that out. You can see the 5/8" plywood, and then some kind of ancient tile (asbestos maybe? I'm wearing my mask during all of this just in case), then 1/4" plywood, and then some self-adhesive vinyl tile. On top of that was the rustic/weathered looking hardwood they had put on which was about 5/8" or 3/4"--pretty thick stuff.
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  13. #13
    DIY Member ironspider's Avatar
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    Here's pic #6

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