Fixing someones mess!

[e-tek]

Hi all. Newb here. I've done some remodelling and construction, but have run into a doosy when I bought a rental home. The upstairs bath (small, about 3x6) had spongy floors. Upon tear-out I found a center joist cut lengthways AND in half for shower plumbing install (Bastards!!). So, I joined the joist with 2x4's screwed to each side, then screwed more 2x4's to those to support the plank flooring. I screwed planks over that, but they ended up being fairly short pieces - not ideal. Over that I put 1/2 ply (again, smaller pieces due to shape of room), then Durock.

Issue I have now is that the Durock, although "fairly" solid is not 100% solid and not 100% level. Should I use a self leveller, then tile it - or should I use a thinset and a final layer of Durock befoe tiling, or ??

Thanks in advance for your help!

[Gary Swart]

Wow! I've done some jackknife carpentry myself, but never anything like that. I'm not personally experienced with tile, but for what I have been lead to believe is the floor must be rock solid before you can lay tile. Any movement will cause cracks. Also, because tile is quite heavy, the under floor has to provide a lot of support. I'm sure some of the guys with more experience with tile can elaborate on this. I don't see how being a little out of level would be a problem with the tile, but it could cause water to gather in a corner which would not be too good. My thought is that vinyl would be a better choice. The self leveling stuff may be a good option for vinyl.

[geniescience]

unscrew the CBU and start over. Make it right before you put any cement board.

[jadnashua]

The cbu (cement backer unit - aka cement board) for industry standards purposes has NO effect in the deflection calculations. The floor MUST be strong enough before you install it. With the planks and then the 1/2" ply, your subfloor is likely strong enough, but the joists aren't. Screwing 2x4's to the joists helps, but may not be all that much, depending on how those joists were hacked up. Glueing then screwing is better, but still may not be sufficient. You may need some steel in there to sandwich the joists.

If you can feel the floor move, tile, no matter what you do on top of the joists, tile are not going to survive. Your best bet may be sheet vinal or linoleum. There may be a way to reinforce it sufficiently, but can't say without being there, or really good pictures and measurements.

BTW, did you install the cbu in a bed of thinset? All manufacturers require this, and omitting that, by itself, could cause failures even if the structure was adequate.

[hj]

Call Mike Holmes. He will cuss the guy who did it, tear the whole floor out, (maybe demolish the entire room and plumbing), install a new floor and then tell you what a good job he did.

[e-tek]

Call Mike Holmes. He will cuss the guy who did it, tear the whole floor out, (maybe demolish the entire rom and plumbing), install a new floor and then tell you what a good job he did.

I was considering that!

Thanks for the replies guys. I'll be removing the CBU, adding another layer of 1/2inch ply, re-setting the CBU (in thinset), then tiling.....

Or maybe I'll just thinset the current CBU joints and glue Vinyl down......

BTW - love my avatar!