Wood floor prep for LVT

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FloorKiwi

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Hello, I'm going to be installing LVT (EDIT floating) in a connected dining room (had carpet), foyer, hallway and 1/2 bathroom (those 3 had ceramic tile). Total is about 250 sq ft. It is a wood subfloor. I will need to add some plywood to bring the foyer, hallway and bathroom up to the same level as the dining room. I have a few questions:

Is there a specific type of plywood I should use (not sure of the thickness I need until I get the rest of the mud set tile removed - ugh)?

What is the best way to attach the new plywood to the existing floor?

What is the best product to use to level some low spots (I have a few low spots in the dining room, not sure of the rest until I finish adding the plywood. I don't think I need to coat the entire floor to bring it to level).

Do I need to fill and sand all cracks, joints and knots in the subfloor? What product is best for this job?

Other prep steps that I am missing?

Total DIY and not in a rush.

Thanks in advance...
 
Last edited:

Tile Tom

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If the new LVT is a floater then it really doesn't matter what you use to raise up the subfloor.
Let's just say if it was me and I needed to add 3/4" subfloor for hight & it was a floater, I would probably go for advantec or dryguard. Their both tongue & groove. I would shift the new layer so seams fall on the joists and you don't have seams lining up with seams in the first layer. I would then use 3" deck screws to secure into the joists and 1 1/4 to pin the sheets together between the joists.

For filling in the low spots I would normally use ardex feather finish and screed that into the lows. If their really big lows then I might think about spot pouring some self leveler (very seldom does it come to that).
And yes....sand your seams flat and fill any & all gaps/ knots that you find. You can do that with whatever patch is left over from filling in your low spots.

Getting your subfloor flat is the bulk of the work in this circumstance. Floaters require the subfloor to be ridiculously flat. Any hollow spots under the finished LVT will cause the floor to flex potentially damaging the locking mechanism. Damaged locking mechanism = flooring failure!
 
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Underlayment panels should be constructed with a water resistant adhesive, be a minimum 1/4" thick, dimensionally stable, smooth and sanded on one side, free of voids and should carry a warranty for use as a resilient underlayment. General plywood panels can be used but actual underlayment panels made for the purpose are better (if you can find them right now). The warranties on general plywood if they are approved for use are generally available at the manufacturers website. Here in the states APA A-B or A-C are generally ok for use as an underlayment assuming they meet those requirements. Luan is NOT an approved underlayment for resilient as it is typically not a full 1/4", can have voids, and can also contain dyes which can stain up through products. If you are using an actual underlayment panel like Multi-Ply, Accu-Ply, IronPly, RevPly, etc. Try and find the manufacturers specific instructions for the panel. Some will want them butted tight while others will want them placed with a slight gap. Some will also want the edges sanded and patched while others may say it's not necessary. In general it's best to sand and patch if you can't find it in the instructions. Note: There are some "composite" underlayment panels on the market. In general I would avoid them as they can be dimensionally unstable.

Fastening with an 18 gauge narrow crown (1/4" nominal) (**Edit: I accidentally typed 1/8" on the original post) width with a chisel point is the most common way of fastening the underlayment. It's important to use the proper staple length for the application. You want your staple to penetrate as far into the sublfoor as possible WITHOUT coming through the underside. If you come through the underside of the subfloor, you will lose 1/3 of the holdi power of the fastener. You also want to pay close attention to your air pressure so that the staple isn't blowing through the 1/4" underlayment. It should place the staple so that it is just flush with the surface of the panel. Not too far in or you'll blow through 1/4" panel or not far enough or you'll end up having to finish setting them with a hammer so they aren't sticking up. I recommend starting around 70-75 psi and then adjusting up or down a pound or two at a time until you get them to set correctly.

For leveling over a wood substrate under resilient a cementitious floor patch such as Ardex Feather Finish, Mapei Plani-Patch, or any other brand of cement based feather patch should be used. These will generally handle fills up to 1/2" in depth in a single coat if needed. Make sure you're not over watering your patch as that can lead to a poor bond or powdering of the patch. (Edit: In addition to what Tom said above regarding self-leveling I would add a couple of caveats - First, most self-leveling products are not warranted over wood substrates without the use of a metal lathe re-enforcement (chicken wire essentially). Second, the pretty much all require a primer be used to bond correctly to the substrate. Without those two things self-leveling over wood can cause the patch to crack or become detached from the subfloor. Again, perfectly doable as Tom stated, just a couple of extra "gotchas" to use them vs. a trowleable floor patch. They can, however, go much deeper (up to 5") in a single application than most trowelable patches.)

Check your work with a straight edge for flatness and once you're within spec, ..."let 'er rip tater chip!".

Good luck with the project!
 
Last edited:

highup

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What is the current subfloor made of? OSB or plywood?
How thick of plywood do you need to bring the floor up to level with the floor that previously had ceramic?
Should we assume that the ceramic tile was installed over HardieBacker or a cement board? I'm assuming it is and that's why you need to bring the new part up to level.
 

FloorKiwi

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What is the current subfloor made of? OSB or plywood?
How thick of plywood do you need to bring the floor up to level with the floor that previously had ceramic?
Should we assume that the ceramic tile was installed over HardieBacker or a cement board? I'm assuming it is and that's why you need to bring the new part up to level.
I believe it is just plywood. I still have to finish the demo to confirm how thick the additional material needs to be. I am not sure about your other question so posting a picture of the demo in progress. Looks like from top to bottom - tile on mudset cement (?), metal wire, roof felt paper nailed to plywood.
IMG_7548.jpg
 

highup

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That is definitely not what I envisioned.
That looks like old school tile setting with a couple inches of mortar underneath it. The demo has to be a total pain in the butt but at least you'll have some clean plywood underneath it because of the tar paper.
 

JCobb

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Underlayment panels should be constructed with a water resistant adhesive, be a minimum 1/4" thick, dimensionally stable, smooth and sanded on one side, free of voids and should carry a warranty for use as a resilient underlayment. General plywood panels can be used but actual underlayment panels made for the purpose are better (if you can find them right now). The warranties on general plywood if they are approved for use are generally available at the manufacturers website. Here in the states APA A-B or A-C are generally ok for use as an underlayment assuming they meet those requirements. Luan is NOT an approved underlayment for resilient as it is typically not a full 1/4", can have voids, and can also contain dyes which can stain up through products. If you are using an actual underlayment panel like Multi-Ply, Accu-Ply, IronPly, RevPly, etc. Try and find the manufacturers specific instructions for the panel. Some will want them butted tight while others will want them placed with a slight gap. Some will also want the edges sanded and patched while others may say it's not necessary. In general it's best to sand and patch if you can't find it in the instructions. Note: There are some "composite" underlayment panels on the market. In general I would avoid them as they can be dimensionally unstable.

Fastening with an 18 gauge narrow crown (1/4" nominal) (**Edit: I accidentally typed 1/8" on the original post) width with a chisel point is the most common way of fastening the underlayment. It's important to use the proper staple length for the application. You want your staple to penetrate as far into the sublfoor as possible WITHOUT coming through the underside. If you come through the underside of the subfloor, you will lose 1/3 of the holdi power of the fastener. You also want to pay close attention to your air pressure so that the staple isn't blowing through the 1/4" underlayment. It should place the staple so that it is just flush with the surface of the panel. Not too far in or you'll blow through 1/4" panel or not far enough or you'll end up having to finish setting them with a hammer so they aren't sticking up. I recommend starting around 70-75 psi and then adjusting up or down a pound or two at a time until you get them to set correctly.

For leveling over a wood substrate under resilient a cementitious floor patch such as Ardex Feather Finish, Mapei Plani-Patch, or any other brand of cement based feather patch should be used. These will generally handle fills up to 1/2" in depth in a single coat if needed. Make sure you're not over watering your patch as that can lead to a poor bond or powdering of the patch. (Edit: In addition to what Tom said above regarding self-leveling I would add a couple of caveats - First, most self-leveling products are not warranted over wood substrates without the use of a metal lathe re-enforcement (chicken wire essentially). Second, the pretty much all require a primer be used to bond correctly to the substrate. Without those two things self-leveling over wood can cause the patch to crack or become detached from the subfloor. Again, perfectly doable as Tom stated, just a couple of extra "gotchas" to use them vs. a trowleable floor patch. They can, however, go much deeper (up to 5") in a single application than most trowelable patches.)

Check your work with a straight edge for flatness and once you're within spec, ..."let 'er rip tater chip!".

Good luck with the project!
I had no idea you would lose 1/3 of the holding power. Wow. Good to know.
 

FloorKiwi

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Thanks everyone for taking the time to reply. To answer some of the questions (after getting access to investigate), the subfloor is 1/2" plywood and the underlayment in the dining room (on top of the same subfloor) is also 1/2" plywood. I am installing TruCor floating 12x24 LVT from their Tile collection. I still have a little more ceramic tile to remove and I know I will have more questions as I get a clean look at everything. The ceramic tile is around the toilet flange. Do I need to be extra cautious with removing tile around the flange? Thanks
Flange.jpg
 

JCobb

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Thanks everyone for taking the time to reply. To answer some of the questions (after getting access to investigate), the subfloor is 1/2" plywood and the underlayment in the dining room (on top of the same subfloor) is also 1/2" plywood. I am installing TruCor floating 12x24 LVT from their Tile collection. I still have a little more ceramic tile to remove and I know I will have more questions as I get a clean look at everything. The ceramic tile is around the toilet flange. Do I need to be extra cautious with removing tile around the flange? Thanks
View attachment 13892
Just don’t pry up on it and you should be fine. Make sure you put the new subfloor under the flange lip to support it. I usually remove the toilet water supply handle when doing a lot of work around them, saves you from a shower at work.
 

FloorKiwi

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Just don’t pry up on it and you should be fine. Make sure you put the new subfloor under the flange lip to support it. I usually remove the toilet water supply handle when doing a lot of work around them, saves you from a shower at work.
Thanks for the tip. Worked great.
 

FloorKiwi

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Joined
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Messages
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Location
48105
Underlayment panels should be constructed with a water resistant adhesive, be a minimum 1/4" thick, dimensionally stable, smooth and sanded on one side, free of voids and should carry a warranty for use as a resilient underlayment. General plywood panels can be used but actual underlayment panels made for the purpose are better (if you can find them right now). The warranties on general plywood if they are approved for use are generally available at the manufacturers website. Here in the states APA A-B or A-C are generally ok for use as an underlayment assuming they meet those requirements. Luan is NOT an approved underlayment for resilient as it is typically not a full 1/4", can have voids, and can also contain dyes which can stain up through products. If you are using an actual underlayment panel like Multi-Ply, Accu-Ply, IronPly, RevPly, etc. Try and find the manufacturers specific instructions for the panel. Some will want them butted tight while others will want them placed with a slight gap. Some will also want the edges sanded and patched while others may say it's not necessary. In general it's best to sand and patch if you can't find it in the instructions. Note: There are some "composite" underlayment panels on the market. In general I would avoid them as they can be dimensionally unstable.

Fastening with an 18 gauge narrow crown (1/4" nominal) (**Edit: I accidentally typed 1/8" on the original post) width with a chisel point is the most common way of fastening the underlayment. It's important to use the proper staple length for the application. You want your staple to penetrate as far into the sublfoor as possible WITHOUT coming through the underside. If you come through the underside of the subfloor, you will lose 1/3 of the holdi power of the fastener. You also want to pay close attention to your air pressure so that the staple isn't blowing through the 1/4" underlayment. It should place the staple so that it is just flush with the surface of the panel. Not too far in or you'll blow through 1/4" panel or not far enough or you'll end up having to finish setting them with a hammer so they aren't sticking up. I recommend starting around 70-75 psi and then adjusting up or down a pound or two at a time until you get them to set correctly.

For leveling over a wood substrate under resilient a cementitious floor patch such as Ardex Feather Finish, Mapei Plani-Patch, or any other brand of cement based feather patch should be used. These will generally handle fills up to 1/2" in depth in a single coat if needed. Make sure you're not over watering your patch as that can lead to a poor bond or powdering of the patch. (Edit: In addition to what Tom said above regarding self-leveling I would add a couple of caveats - First, most self-leveling products are not warranted over wood substrates without the use of a metal lathe re-enforcement (chicken wire essentially). Second, the pretty much all require a primer be used to bond correctly to the substrate. Without those two things self-leveling over wood can cause the patch to crack or become detached from the subfloor. Again, perfectly doable as Tom stated, just a couple of extra "gotchas" to use them vs. a trowleable floor patch. They can, however, go much deeper (up to 5") in a single application than most trowelable patches.)

Check your work with a straight edge for flatness and once you're within spec, ..."let 'er rip tater chip!".

Good luck with the project!
Tried using the feather finish on a few low spots. Man...troweling that stuff is an acquired skill. Going to have to do a few application to get it smooth and to the level necessary (if I can ever get there).
 

C.J.

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If you can define your low spots it might be a bit easier to dump out some feather finish and use some sort of a straight edge to screed the low spots. It won’t necessarily be as smooth as if you troweled it but it will fill in the low spot to an acceptable level. Let that dry then go back with a second coat to smooth it out and make it look purdy.
 

FloorKiwi

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Messages
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48105
If you can define your low spots it might be a bit easier to dump out some feather finish and use some sort of a straight edge to screed the low spots. It won’t necessarily be as smooth as if you troweled it but it will fill in the low spot to an acceptable level. Let that dry then go back with a second coat to smooth it out and make it look purdy.
I'll give that a shot...thanks.
 

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