LVP in bathroom; Water damage in subfloor?


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Old 06-15-21, 12:30 PM
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LVP in bathroom; Water damage in subfloor?

I pulled up the vinyl in the bathroom with the intention of laying LVP to match the rest of the unit, and found there was significant water damage around the toilet and bathtub:



Close-up of the rot around the tub area:



My questions:
1. The toilet seems to be working normally. How can I confirm there is no active leak? I plan on replacing the toilet anyways, but want to confirm there's nothing more sinister going on.

2. What's the proper repair for the toilet area? My current thinking is just to clean it (e.g. mold armor) or spray it (e.g. kilz).

3. What's the proper repair for the tub area? I could replace the top 0.5" layer of particle board. Is that sufficient or do I need to deal with the wood underneath the particle board (the darker color with the white coloring)?

Overall, what would you do to replace the flooring here? Can I just patch things up, or do I need to lay another layer of wood as underlayment, or rip everything out and replace? This is for a rental so looking for a relatively cheap/straightforward fix.
 
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Old 06-15-21, 01:30 PM
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1. You are pulling the toilet so worrying about that is pointless. If there was a leak around it, it would be obvious and would be the wax ring, from the toilet rocking.
2. Pull the toilet to replace all the particle board.
3. Particle board should never have been used in the first place... it is the worst thing to use for subfloor, especially in a bathroom.. remove all of it and replace with plywood or osb.

Once all the particle board is out you can assess the condition of the plywood below. If it is too far gone you might need to replace a patch here or there, but if its still in good shape you might just be able to spread a little Durham rock hard putty over the "rough spots" just to ensure you don't have any dips that telegraph through the next layer of subfloor.

If that layer of subfloor has stinky urine smell around the toilet that would be another reason to replace a patch of it. The flange needs to be solidly bolted, so that the toilet can be solidly bolted to the flange.

And the top layer of subfloor should just be screwed or stapled to the plywood below it. No glue, no fasteners into the joists. Screw/staple 6" on center everywhere.

You will put the toilet back down after the flooring is done. And you typically want to seal the flooring to the flange with some silicone so that if there is ever a leak, it leaks on TOP of the new flooring, not under it where it would go unnoticed.
 
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Old 06-15-21, 10:10 PM
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Thanks for the clarification on the toilet, glad that's not an issue.

Replacing the entire subfloor is a bigger project than I'm looking to do, but will if absolutely necessary. How "bad" would it be to only replace the subfloor near the tub corner? This isn't an area that someone would walk on, so it's not structural. I'm primarily interested in making it level so I can lay on the new flooring.
 
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Old 06-16-21, 12:26 AM
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That particle board must be removed. It was the wrong material to use in the presence of water.
It must be replaced with something that can handle water without crumbling. Plywood is best.
 
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Old 06-16-21, 04:19 AM
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You must have a rock solid floor around the toilet. If there is any "softness" in the subfloor it can cause the toilet to leak again. Replacing any suspect subflooring is often required.
 
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Old 06-16-21, 09:59 AM
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OK, so right now the top layer is 0.5" particle board, which makes the bathroom 0.5" higher than the adjoining hallway subfloor. Since the bathroom was vinyl and the hallway was carpet, they are almost the same level.

My question: What should I replace the particle board layer with? Luan plywood, 0.5" plywood, or both?

I was planning on doing LVP in both hallway and bathroom, but then I'd need a reducer/transition piece. Alternatively, I could put a nicer vinyl in instead. Recommendations?
 
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Old 06-16-21, 10:35 AM
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My first choice would be Advantech which is a premium OSB product that is extremely moisture resistant. You could also use plywood. An exterior rated grade would be better. Avoid particle board and luan like your life depends on it. Those are terrible materials for wet environments.
 
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Old 06-16-21, 12:50 PM
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Do you have a recommendation on thickness?
 
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Old 06-16-21, 02:19 PM
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Well, if you need 1/2" to make the elevations work then I'd go for 1/2". Keep in mind that most sheeting isn't an even half inch so you'll see various fractions that are close.
 
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Old 06-16-21, 02:43 PM
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To make the flooring exactly even with the hallway, I'd rip out the top layer of subfloor and add nothing. 1/2" would make it the same as right now. I think a transition can handle 1/2", so it'd have to be that or less. I guess my question is more, "is less ok", such as fraction closest to 1/4"? Or would that not be advisable (e.g. too much flex or not flat enough for lvp).
 
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Old 06-16-21, 05:40 PM
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We don't know anything about the size of what's under your particle board... So, kind of hard to say.
 
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Old 06-17-21, 02:54 AM
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You also need to pay attention to the toilet flange if you are changing the floor's elevation. If you lower the floor you might have to lower the toilet flange. You can only tell after you've removed the toilet.
 
 

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