Bathroom Subfloor Issues

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Old 07-15-09, 10:35 AM
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Bathroom Subfloor Issues

Hi, I am new to the forum and relatively new to DIY. I have taken on the task this summer of gutting a master bathroom adjacent to my bedroom. The is mostly done.

I have removed EVERYTHING. I have just under a 6' x 6' bathroom that will have a neo-angle shower stall, toilet and sink. The floor joists are 2x8 and 16" apart. Due to subfloor rot, I removed the existing 1/2" plywood subfloor and the 3/4" cement and wire lathe that was under the original 1977 tiling.

I intend to fasten 3/4" Georgia Pacific plywood to the joists with 2 1/2" moisture coated hex head screws and some Liquid Nails. The problem is, after I clean up the edges a bit today, I have a 5 1/2" gap on one side of the bathroom (behind toilet and under shower stall) and a 2" gap at the entrance door. The plywood would 'overhang' these gaps and I think that would be unacceptable.

In addition (to make things more fun), the back wall of the bathroom (near the 5 1/2" gap is now resting on overhanging plywood itself - and is supported by nothing else. So, on that side (another bathroom), the wall is on the original 1/2" plywood and about 10" off of the joist.

On the other side (the 2" gap at the bathroom entry), the floor sags (visibly) when I step there because it too is overhanging the joist by about 14".

So, aside from telling me I should not have cut the plywood between joists, I am in a hole!

A friend suggested that I place pieces of 2x6 perpendicular to the joists either by making a hole in the ceiling below and screwing it into the two joists it will be between or by buying a deck bracket and mounting the 'crossbeam' on that to avoid cutting the ceiling below. In either case, I would then tighten it up with shims and maybe screw from above where possible.

HELP!!

Bathroom Renovation - a set on Flickr
 
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Old 07-15-09, 04:20 PM
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You did well by gutting the room. At least you know all the boogers, now, and not later. I am afraid your friend is right, but you may not have to tear up the ceiling below (although it would be better if you did). Along the wall where the plumbing is, measure and cut perlins and place them from your last joist to the one under the wall, and attach it with 3" screws from the top of the bottom plate, and into the end of the exposed joist. That will help transfer the weight. You'll need to mark the bottom plate where they are, since I am sure you won't get an exact 16"oc with all that piping. But at least you will have support.
Where the notch is cut for the drain line (plumbers are people, too), you should span a perlin back to the good joist as well, or you may get squeaks from your joist in that location.
I am assuming the hardwoods stay, so you have to drop back and punt, here. You may have to go under, remove some sheetrock and install cross framing for support at that critical point. You will need to support not only your plywood, but the hardwood flooring as well, so put in probably 3 perlins to spread the weight.
Keep us posted, and let us know if we can help further.
Don't worry, this isn't the last word, as others will chime in shortly, so hang on.

Larry
 
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Old 07-15-09, 06:25 PM
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Thanks

OK, this gave me a great idea, thanks, I will use my 2x8 pressure treated lumber and 'go nuts' putting as many of these as possible on both the entry way and below the pipe / wire wall with 2 1/2" moisture coated screws.

I will attach them to the base plate on the wall side and to the joists. Next week, I will have a helper (good tape guy) come by and open the ceiling and screw them on to the other joists from below and clean up the holes.

I will use shims to 'push up' on the wall and entry floor from below and shim the walls around the current joists to minimize movement. Do you think this solution will allow me to go forward with the 3/4" plywood sub-floor before the guy fastens them from below next week? Is there such a thing as 'too tight' when adding shims to minimize movement in the joists? Will this hold the ceramic tile floor I will install on top of it that - if it cracks - will mean my wife will murder me?

Thanks again Larry!
 
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Old 07-18-09, 06:49 PM
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I think you have a good plan of attack. Shimming will require a direct relationship with a wall below and what you are adding, and I know you know that. Once you have the proper support across the room, add your Advantech subflooring, then your cbu. You should have no issues of the tile cracking once the support is in and you span it with wood and cbu first.
Keep us posted and let us know if we can be of further help.
 
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