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MoldyJay 01-08-2011 09:05 PM

Removing rotten bathroom subfloor
I have just discovered after trying to replace a toilet thAt the subfloor in our upstairs bathroom is rotten around the soil pipe. I have just finished adding shutoffs to the vanity so I could remove it and the flooring. Now that I have a better look at the floor I see that it is pretty bad looking up to the wall which borders my bedroom, and to the tub. I don't want to have to tear out the tub ... This was supposed to be a 30 min job to fix a toilet. Where should I tear the subfloor out to.
Also I plan to install slate tile after so I understand that also requires specific underpayment.

MoldyJay 01-08-2011 09:10 PM


MoldyJay 01-08-2011 09:13 PM

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Pics are here

MoldyJay 01-09-2011 07:31 AM

Please help someone

MoldyJay 01-09-2011 08:45 AM

Still need help with rotten subfloor
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Please see my other are the pics... I need to know how far to rip out the subfloor...I am laying slate tile after

Clutchcargo 01-09-2011 09:18 AM

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If it were me, I'd pull the tub and take all the wet wood out.

oh'mike 01-09-2011 09:25 AM

Jay---Yuck! You are not alone--this is very typical damage----

You will need to cut that back until you find good solid subfloor--Find the location of the floor joists-
Cut the bad flooring down the center of the joist--use 2x4 blocking under any seam that is not supported by a joist--Screws are best for fastening down your new plywood--Do not use OSB-it is to weak for slate-

After the subfloor is patched,add another layer of 1/2 inch B/C plywood on top,for proper stiffness.

Then 1/4 inch durrock or wonder board,set in thinset---I'll see if any one else has any suggestions.--Mike--

MoldyJay 01-09-2011 09:53 AM

The wood right by the tub does not seem to be wet just black on top from old adhesive. I've been gouging at different spots to test the wood and it seems to just be ok right beside the tub and wall, although it's definitely rotten around the pipe and a little to he right of it.
I would like a nice new base to lay my slate on anyway. Just not sure how far to cut the subfloor. It's about. 25 square feet

MoldyJay 01-09-2011 09:58 AM

Also the joists run perpendicular to the way the tub runs so you can visualize where they are in relation to the picture

AllanJ 01-09-2011 10:08 AM

Is that a metal tub or a plastic/fiberglass tub?

If not metal I contend that the outside edge of the tub is not load bearing. Even if it is load bearing and if you have to undermine to get rid of all the rotten wood for not more than six inches along the front of the tub, then you are still okay.

I would leave at least two inches of wood in front of the tub.

It is possible that the existing subfloor is not thick enough to support slate. Too much give and the slate will crack. You might get around that by adding more joists for stiffness' sake. Extra framework of wood below and just in front of the tub would let you end the extra joists there and not remove the tub or the ceiling below.

Or add another layer of subfloor. The edge of the tub might look funny now that part of it is below floor level.

MoldyJay 01-09-2011 10:27 AM

The tub is a fiberglass whirlpool. The existing subfloor is most likely original '78, and is 3/4 ply. I have a circular saw and a recip. Saw should I leave 2 inches in front of the tub and go right to the wall everywhere else?

oh'mike 01-09-2011 10:34 AM

Jay--You have duplicate posts going on the same subject---That leads to confusion--I answered this question elsewhere--Please don't do that.Mike

Bondo 01-09-2011 10:42 AM


Originally Posted by oh'mike (Post 566056)
Jay--You have duplicate posts going on the same subject---That leads to confusion--I answered this question elsewhere--Please don't do that.Mike

Ayuh,... That duplicate thread Mike mentions is Right Here...

MoldyJay 01-09-2011 11:45 AM

Sorry about the duplicates.. My head is in too many places right now and the wife is driving me crazy. So just to clarify I should put down 3/4 ply subfloor. Then stagger the joints and lay a 1/2 of underlay, and then set 1/4 durock on a bed of thinset. And then I would assume a medium set on top to set the slate?

Jackofall1 01-09-2011 12:07 PM

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Had the exact bathroom except mirrored, heres what I did, but I removed the bath tub and built a custom shower. All the wood missing was rotten, joist were OK.

Attachment 28503

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