Floor Prep for LVP help

Discussion in 'Floor Preparation' started by Mike575, Dec 2, 2019.

  1. Mike575

    Mike575 Member

    Hello all and thank you for your assistance. I have been trying to install Coretec LVP in my kitchen, a hallway, and combined family/dining room and I need some guidance. I have mid 80s home on a previously damp crawl space and when I removed the carpet and tile, just under 600 square feet, my OSB subfloor made this project a handful.. Last year the crawl space was encapsulated, but I have multiple dips between joints, some dropping 3/4 inch. I put screws in about every 8 inches or so, belt sanded the high spots, vacuumed relentlessly, and used more Henry 345 Premix then I care to admit in the low spots. I installed about half the project, but I still feel some small movement in the LVP and can hear slight clicking so I am not happy. I’ve read more about SLC but I would have to divide up the space and work mostly by myself, so I’m leaning against it and towards 1/4 underlayment? I’m wondering if I’m thinking correctly and if I install underlayment, do I simply staple or nail up to the patchwork? I’ve read you can’t nail or drill the patches and there seems to be plenty of voices against glueing the underlayment down, but since some is by the wall and in the hallway I’m hesitant. Any and all suggestions would be appreciated!!


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  2. Incognito

    Incognito No more Mr. Nice Guy! I Support TFP Senior Member

    did you use a primer?
  3. Mike575

    Mike575 Member

    The premix doesn’t require primer like their SLC products to my understanding, so I didn’t no.
  4. kwfloors

    kwfloors Fuzz on the brain Charter Member Senior Member

    What is the clicking, movement of the planks over a non flat surface? Or is it the substrate OSB moving? I would do what you did with patch over slc for that situation and have put that product into the same situation with no problem. Make sure the floor it flat and dry so nothing sticks.
  5. Mike575

    Mike575 Member

    I think it is the LVP installed on a not perfectly flat subfloor as it has plenty of screws to hold it down.. Are you in agreement that SLC isn’t the best option? If I were to use SLC, again unfortunately I would be doing it by myself, I would not be able to do the entire space at the same time, and all the SLCs I’ve found available locally require metal lath. What are your thoughts for underlayment?
  6. Premix is for small spots, really, I’ve never used it in the patch form due to cost.

    You’re really asking too much of the lvp for its substrate. Patching wood there’s not really a good product to flatten and then nail into.

    Underlayments(Plywood type) are for covering already flat floors. They follow contours.

    There’s an attached underlayment to vinyl?

    With an unflat substrate problems occur to The lvp. The movement you hear and see now result in the joints separating/breaking.

    You’ve been hyped into thinking it’s easy, yes when Floors are flat to begging with. People choose flooring first, then ripup and find issues for the new product.

    No to self leveling products, another hype you’ll be led into.
  7. Mike575

    Mike575 Member

    100% agree on the premix. I originally didn’t think the difference was that great.

    The product is 8mm with cork underlayment attached.

    What would be your proposed solution?
  8. It’s really difficult to answer without fully seeing the entire project.

    Movement of wood is a rigid patch killer, it simply will not stay bonded. You say you had Tile, was that ceramic and it was cracked?

    Carpet was an answer, sheetvinyl could be another.

    If someone has an answer to unflat wood subfloors as you’ve described for patching then plywood underlayment it’s not been divulged to me. I’ve been on this site maybe 6? Years, hadn’t seen the answer.

    I’m not sure many even installers are capable of flattening your floor. Hmm, a tilesetter asked us months ago to level a floor, porcelain plank was going down, he was hard to understand, but I had laser shot the entire house previously, he had low areas marked that he wanted us to grind, needless to say I looked at my brother and shook my head no, we walked away. But dam I’m curiously now
    What/how it came out.

    There’s another product XL, it just lays side by side, no connecting. But pricey.

    So what occured was someone came up with the idea of connecting vinyl, laminate ran its course, a bit stronger locking mechanism, this vinyl plank took off like wildfire, fine if the floor is flat, write up in the install instructions flatness standards to manufacturers advantage, anything outside of parameters the manufacturer is off the hook. Sell the company to larger manufacturer because the numbers show it will make a large profit, regardless of the failures.
  9. Chris 45

    Chris 45 Director of P.R. on some deserted island. I Support TFP

    The moisture from your damp crawl space weakened the subfloor and allowed it to sag. Could be insufficient subfloor thickness as well. Those sagging sheets will never straighten themselves out even if they dry out. You can block them up from underneath or replace them. Thats a lot of work and is usually a deal breaker for a paying customer.

    So without tearing your house apart I think you’re doing what you need to do. I would prefer to use a combination of door skins and roofing felt to build up the dips then ideally another layer of 1/2” underlayment would go down.
  10. What straightedge are you using, ie 10ft?,6?

    So the flooring is floating, you’ve eliminated the need for it to bond to substrate, the only thing the patch is doing is flattening and supporting the plank. Should it separate from the OSB (movement caused by deflection or moisture content changes.)it won’t fail, all it has to do is stay there and be quiet(not make crunchy crackly sounds.

    Is the crawlspace now climate controlled?
  11. Mike575

    Mike575 Member

    The house had a tile entryway by the front door and also tile in the kitchen with no issues besides me not cleaning the grout. It was installed on a cement backer board should you care.. and carpet hid the majority of the nonsense.

    I was using a 6 ft board and 4 ft level to get the results I currently have.

    For the crawl space, the encapsulation has maintained humidity to acceptable levels. The HVAC plenum, supply run and off shoots to vents are there, but there is no vent.

    I had considered a larger plywood underlayment like 1/2” vs the 1/4” but that’s was also part of me reaching out here for more experienced perspective
  12. kwfloors

    kwfloors Fuzz on the brain Charter Member Senior Member

    Thicker plywood would help bridge the lows. I have installed a lot of coretec over worse floors than you have never heard any clicking or squeaks.
    • Like Like x 1
  13. Yes I care, all the info is relevant. Had the tile been broken it would have been an indicator of possible substrate issues. Sometimes the tile unbonds from what it’s attached to and just lays there without notice.

    Underlayment of the plywood type 1/4” just follows the current subfloor, it’s contours etc. or if not fastened sufficiently to the recommended APA/manufacturers recommendation the air gap can occur. A 1/2” sheet provides more rigidity yet there will be air gaps and weight applied can cause movement .
    The 600 ft is part of the issue as it’s no small kitchen, a few sheets of ply no problem. That’s why I suggested maybe a carpeted area but I understand the areas you stated were not typically carpet.

    So your not in an easy fix situation, you have to weigh the choices, my way of decision making is do you benefit from that choice and is it worth the return.
  14. Mike575

    Mike575 Member

    I was able to have a local contractor referred by a coworker swing by and check it out. His opinion was my current work was better than some install jobs he’d seen and I should drive on as is to complete the job. Unfortunately the minor movements I feel are bothering me. He said it’s a floating floor and its fine. I still am unsure if I should put down underlayment or not. With the patchwork down the potential for air pockets is there, so I don’t know if I’ll fix it all or create an issue I can’t fix. Leaning towards underlayment to minimize the variation..?
  15. I walked on a floating laminate floor the other day at a house we were removing “floating tile.” The laminate was crackly and to me sounded awful. If you add roll underlayment I don’t think it’s going to help and voids warranty. Plywood underlayment may not be a fix either if you nail it then there can be squeaks. I’d say there’s slight movement when the floor is flat and some people way associate that with easier on their backs than tile is a phrase I hear.

    Hey I’m living with popcorn ceilings I despise but not walking on it.
  16. I still don’t know the exact situation but if sagging was only in the middle and joists were all level/flat could some molly bolts be used to lift the sag and screw 1/2” ply down, then release the Molly’s and patch. Just a thought should others run into situation.
  17. Mike575

    Mike575 Member

    Ok so if SLC is clearly out, should I rip it all up and attempt more patch and felt to remove low spots or use underlayment?
    Some spots are very solid, some are clearly a little low and are visible.. some audible
  18. I’d just patch over what you have and do it right on the next house.
    • Agree Agree x 1
  19. Mike575

    Mike575 Member

    Ok thank you. For my own learning, what is your take on the right way to do it
  20. I think about 5 homeowners that I know of on this site removed the subfloor, various reasons, particleboard, joists not flat etc. Then depending on product a plywood underlayment maybe. If it’s as bad as you say? 3/4” sag 24” on Center I assume.

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