Subfloor repair

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  #1  
Old 04-16-13, 11:16 AM
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Subfloor repair

I'm just finishing stripping down my bathroom and I've reached the point where I need to decide how to repair the subfloor; I'm looking for some advice on how I should do it. Here's a link to an album containing pictures, but I'll try to explain as good as I can: https://plus.google.com/photos/11086...NCxm8DI_rPVpgE

My initial plan was to cut the subfloor out completely and start from the joists. I don't think that is a viable option now; there are a number of layers of subfloor (pic 5). I suspect the current subfloor level is 2-3" above the joists, which is roughly 3/4" below the level of the finished floor of the room it connects to. I bought enough 3/4" plywood to do a single layer, but obviously that would leave my floor too far below the conjoining room. My plan is to lay down 1/4" hardie backer then tile, which would add maybe another inch.

Additionally, if you look at the first picture, you can see there are 2 sections of subloor; underneath where the tub was there was added at some point another layer of t&g flooring. This is fairly level, but they left a pretty gaping hole underneath the tub drain. I'd like to reinforce this at the least, so any advice on that would help.

The primary concern is the remainder of the floor; it slopes quite a bit from the outside wall to where it meets where the tub was; in the middle of that it's about 3/4" below the tub subfloor (however, it feels perfectly solid). I'm wondering now if it would be ok to use a leveling compound in this area, to bring it up to level with the subfloor under the tub. If so, should there be anything I put underneath it, or just pour right onto the floorboards? Also, there are a few spots near the tub where it would leak into the basement; what would the best way to seal these areas be? Alternatively, I could attempt to remove a single layer of the current subfloor, level that, then lay my plywood down. If so, what would be the best way to do that preliminary leveling?

If at all possible I'd like to avoid trying to adjust the joists; this house is very old and I'm not sure I'd succeed without damaging other parts of the house. Let me know what advice you have. Let me know if there is any other pictures or info I can provide. Thanks!
 
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Old 04-16-13, 04:59 PM
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I made a decision since I posted this: I decided to remove the top layer of subfloor. I plan on putting down a new layer of 3/4" plywood, but I still haven't figured out if I'm going to try to shim underneath to try to bring the plywood to level, or just screw the plywood down and use SLC on top of that. With both options I'm worried I will end up with gaps between the subfloor layers that will lead to instability in the floor, more so with the second option. I'd prefer to use the SLC then put plywood on top of that, but as I understand that's not a good idea. Any opinions are appreciated.
 
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Old 04-17-13, 04:16 AM
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I think I'd still be inclined to remove all the sub floor and then either shim the floor joists or sister new ones along the old joists to get everything level and at the right height. That will allow you to level the new floor along with inspecting the framing so you can fix any other issues that might be in play.

Depending on the type/size tile used, 3/4" subfloor often isn't enough. Common practice is to have the 3/4" sub floor and then add 1/2" of plywood before installing the cement board and tile.
 
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Old 04-17-13, 04:45 AM
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5 layers? would not have believed it if the pictures did not show it. Tell us a little about what is underneath the 5 layers. What size are the floor joist, what are the spacings between joists and how long is the unsupported span?

Is the rest of the house built up like this? Or what this a sunken room at one time that has been built up?
 
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