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Thread: Subfloor wetness problem for end grain flooring

  1. #1

    Subfloor wetness problem for end grain flooring

    Ok, so here is my problem. I am going to do an end grain flooring using red wood 4x4 tiles 1 inch thick. The room is an old enclosed lanai that is a step down from the rest of the house. So I made joists and laid down plywood so the tiles would match the height of the rest of the house. Simple enough.

    Problem is that the ¾ inch plywood I got from the local hardware store came wet. Like when they pulled off the tarp the whole stack was quite wet. Because I wanted to finish the job while my helper was available, and I supposed because I am not too bright, I took the plywood anyway. They were cupped a bit so I laid them out in the sun on the driveway with the bow facing up. They stayed there for a few hours while we measured and prepped then cut the boards and installed them. Since i knew there was the bow I screwed down one side and worked against the bow so the screws would pull the plywood flat. I had someone stand on the bowed areas while I drove the screws into the 2x6 joists.

    Now, after talking to a flooring guy I am realizing that this may take a while longer to dry. It has been a week since I installed them and i bought a moisture detector which read almost 50% when poked in deep into the plywood. So now as the plywood dries I notice it still isn't that flat. Part of it I think is just imperfections in CDX plywood as I have small ridges but also it appears there may still be some bowing in the wood. Some nails pulled up a little so I added extra screws to be safe. So my question and dilemma is where to go from here. I can see that there are slight gaps forming at the seems where the plywood met which I am assuming is shrinkage? Since I have screws holding the plywood mostly flat, will it straighten as it dries or will it get worse? I have to cut about 1450 of the redwood tiles which will take me a while so I do have some time before i am even ready. The room also gets a good breeze so I am hoping it dries quicker rather than slower. Worst case scenario is someone tells me I have to rip out all the plywood and start over. I am hoping that just waiting a while will be good enough? This is in Hawaii where we do have a humidity level of anywhere from 50-85% depending on the time of day and weather.

    Thanks in advance for any suggestions!
    Last edited by Matt Uchida; 03-27-2017 at 2:10 AM.

  2. #2
    Join Date
    Dec 2007
    Location
    Minot, ND
    Posts
    558
    It is critical for a good flooring job that both subfloor and finish flooring are at equilibrium before installation. Both with your environment, and with each other. As such, your plywood sub floor needs to dry out before you proceed. If it is held down securely, it will dry in placewithout excessive warping. If you get curling of the edges, you need to make sue the subfloor is flat prior to installing the finish floor. I've used a belt sander to flush up joints in the past. Small gaps between the plywood panels shouldn't be an issue. Actually, they are preferred so squeaks don't arise from panel edges rubbing against each other. Testing with your moisture meter should work. Just make sure you are getting accurate readings. When both types of flooring are at the same moisture content, then you should be okay to proceed, (assuming you are in equilibrium with your environment.)

    Good luck with your project and post pics. An end grain floor is a lot of work.

    Clint

  3. #3
    Quote Originally Posted by Clint Baxter View Post
    It is critical for a good flooring job that both subfloor and finish flooring are at equilibrium before installation. Both with your environment, and with each other. As such, your plywood sub floor needs to dry out before you proceed. If it is held down securely, it will dry in placewithout excessive warping. If you get curling of the edges, you need to make sue the subfloor is flat prior to installing the finish floor. I've used a belt sander to flush up joints in the past. Small gaps between the plywood panels shouldn't be an issue. Actually, they are preferred so squeaks don't arise from panel edges rubbing against each other. Testing with your moisture meter should work. Just make sure you are getting accurate readings. When both types of flooring are at the same moisture content, then you should be okay to proceed, (assuming you are in equilibrium with your environment.)

    Good luck with your project and post pics. An end grain floor is a lot of work.

    Clint
    Thanks for the advice. Sounds like I am on the right track as long as I let the plywood dry. I will hit the high or spots with the belt sander. Hopefully the urethane glue will take up some of the difference.

    I just bought 17 pieces of 4x4 redwood. Have to clean up the edges to make them nice and square and then get to cutting. Probably about 1500 blocks to cut. Did some samples and I think they will look nice. The redwood I bought has large portions of light wood which should make for a really nice color combination! I will post pictures when done.

  4. #4
    Join Date
    Dec 2007
    Location
    Minot, ND
    Posts
    558
    Quote Originally Posted by Matt Uchida View Post
    Thanks for the advice. Sounds like I am on the right track as long as I let the plywood dry. I will hit the high or spots with the belt sander. Hopefully the urethane glue will take up some of the difference.

    I just bought 17 pieces of 4x4 redwood. Have to clean up the edges to make them nice and square and then get to cutting. Probably about 1500 blocks to cut. Did some samples and I think they will look nice. The redwood I bought has large portions of light wood which should make for a really nice color combination! I will post pictures when done.
    I would be afraid of the expansion and contraction of a floor like that. I'm guessing that being in Hawaii that you don't have the large humidity swings prevalent in areas with larger temperature swings. Even so, i wonder if a floor that thick might have a tendency to buckle if the humidity changes enough. If the wood gets a chance to absorb enough moisture, you can't get enough glue between it and the subfloor to hold it in place. Likewise, if it loses enough moisture, you'll end up with gaps appearing between your tiles. I've seen and installed parquet floors and flooring before, but never with the end grain oriented vertically.

    Again, be interested in seeing how it comes out.

    Clint

  5. #5
    Quote Originally Posted by Clint Baxter View Post
    I would be afraid of the expansion and contraction of a floor like that. I'm guessing that being in Hawaii that you don't have the large humidity swings prevalent in areas with larger temperature swings. Even so, i wonder if a floor that thick might have a tendency to buckle if the humidity changes enough. If the wood gets a chance to absorb enough moisture, you can't get enough glue between it and the subfloor to hold it in place. Likewise, if it loses enough moisture, you'll end up with gaps appearing between your tiles. I've seen and installed parquet floors and flooring before, but never with the end grain oriented vertically.

    Again, be interested in seeing how it comes out.

    Clint
    Yeah, our humidity doesn't swing as much but it can get high and remains fairly humid year round. Temperature swings would be from about 60 to lets say 95 degrees. I wonder if end grain flexes differently than compared to traditional flooring. Everything I have read says it is a very durable floor material, used for roads a hundred years old which are still in use. Probably not with our level of rain though!

    Would the polyurethane floor coating help with issues of expansion? Currently the rest of the house is solid oak and fairly thick which is standard for this area.

    I will post pictures when done though. Currently I am setting up my miter saw to make good consistent cuts. Then gotta plane the 4x4s and then cut them so it may be a month before everything is done. Again, thanks for the help.

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