Hello all, and thanks in advance for the help to come. I recently gutted my 5x12 bathroom, installed shower and new tiles, that went perfectly, however the floor I screwed up and I'm literally in middle of removing it. My mistake, I used 1/4" goboard over 3/4" wood subfloor. I screwed it down very securely, didn't think I would have an issue. By the way, this is a 2nd floor master bath in our Townhouse. 2nd mistake, I used a 1/4" trowel with TEC Tile Adhesive from Lowes. Needless to say, after everything cured for 2 days, grout started to crack, therefore I knew it had to come up, no way I want my wife or I to be stepping on shards of grout in the coming weeks after starting to use. I'm currently halfway through pulling all the tiles up, and I'm noticing after a week that the mastic is still plyable and not fully dry. I went and purchased 3 sheets of Hardie Backer board and plan on putting this directly over the goboard and sealing it, so that 1 1/2" of floor thickness, should be zero flex or deflection. My question, will this work? Also, am I ok using mastic as long as grout seals everything up, I know mastic is not waterproof, but I've seen bathrooms built this way and they are still in great condition after years. Where should I go from here? Thank you again.

 

Welcome to the forums! Goboard and Durock or Hardiebacker won't make he floor more deflection resistant. I feel your problem was using mastic, since it never really hardens and can be softened with moisture. In addition 1/4" trowel was way too big for mastic. The movement of your flooring on the mastic probably was the cause of the grout cracking.

Were you able to remove the mastic? You may be able to use thinset over a slight residue, but would recommend removal and replacement of the goboard. Then thinset and tile.

 

I got all the tile up and scraped clean, very small thin amount dried on back of the tiles, I'm definitely going to use mortar from this moment on, valuable lesson learned. Do I have to take the goboard up, or can I just sheet the hardieboard over it? Thanks again.

 

And what size trowel do u suggest as well, thanks

 

Did you use mastic under the goboard as well? As you know, mastic will sit on the shelves of a retail store for years in a tub and not set up. Now you have it under a waterproof goboard. How will that dry out? I think you need to pull that up as well.

 

I only used the suggested screws for the goboard over the OSB, no mastic

 

1/4" is fine with thinset, just not with mastic. Could you post a couple of pictures of the floor so we can see what you see? http://www.doityourself.com/forum/el...your-post.html

 

Then backing out the screws will be rather easy then. You need to spread thinset under the boards to fill any voids and make for a super stable surface. It is a key step in any backerboard installation. You have failed once, don't set yourself up for a second failure. I guarantee that the thinset will be harder to fix than the mastic.

 

This is before the goboard went down

 

Ok, up comes the goboard, spread thinset and lay the hardieboard, then screw down, then I can set tile using thinset, no mastic ever again using a 1/4 trowel. Got it, thank you both. In the past I dealt with concrete floors only, never dealt with a subfloor. Thanks for the great advice thus far

 

You would find it a whole lot faster, cheaper and not have to deal with screw heads that will not sit flush if you used galv. 1-1/4 roofing nails instead.