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nywvblue 01-29-2010 08:59 PM

Densguard & tile caulking question
I'm using Densguard around my tub, installed it about 3/8" from the tub's horizontal surface, which leaves a considerable gap (3/8" x 1/4" - the thickness of the Densguard itself). I'm about to set my last row of tiles which rim the tub, and those will sit about 1/8" away from the tub's horizontal surface.

I'm concerned that if I caulk only after setting the tile, the big space behind the tile won't get properly sealed. Should I caulk the Densguard/tub gap first with Silicone then caulk again after I've tiled the smaller tile/tub gap with another kind of sealant? I've made every good waterproofing move so far, really hate to blow it now!

Many thanks!

Maintenance 6 01-30-2010 07:18 AM

If you create a big, fat caulk joint it likely won't be able to move enough without tearing loose. I'd use a non-absorbant backer rod in that space. Closed cell foam rod would be the best. Then your caulk joint will be between the tub and the bottom of the tile. The link below will give you some idea of proper joint design.

nywvblue 01-30-2010 10:03 AM

Thanks so much for the tip. Good info there! I also tried calling Densguard's customer service number but got the ol' 8-5 M-F auto answer.

I just read on thetiledoctor site this nugget:
The DenShield and or CBU must be 1/4" above the tub or pan surround. This cavity should be filled with mortar or tile caulk before setting the tiles. Tiles should not sit directly on the tub or surround and should be lifted at least 1/8" with shims or wedges. You have taken great pains to prep your project, don't short change yourself now. Space all your tiles where they meet in the inside corners the same width as the rest of the grout joints in the installation. Good Luck, Armen Tavy
He posted this back in July 2008. Not sure what he means by "tile caulk" specifically -- I'm still stuck on the silicone vs acrylic question and whether I can caulk over a previous bead if need be.

JazMan 01-30-2010 12:02 PM

Hi Blue,

I guess you're almost finished. First of all I must tell you that you used the wrong thickness board. 1/4" is for floors and counters, not walls. Walls get the 1/2" board.

So, if it's too late, just go ahead and silicone that joint so water will not enter the cavity. May have to do it twice if it droops. Set the tiles as you said within 1/8" of the tub and then caulk with a color that matches your grout.

BYW, did you use thin set (powder) or some pre-mixed adhesive?


nywvblue 01-30-2010 12:55 PM

Excellent, thanks Jaz.

And, yeah, the 1/4" IS flimsy stuff -- I commented on this to my dad numerous times as I was tiling. (He's 71 years old and the 1/4" was all he could handle.) I've been counting on the thinset and the 6x6 tiles to give it some strength, which it has, but...well...mustn't think about the "what ifs" now.

I used a premix thinset mortar -- Home Depot carries it -- SimpleSet for Stone, Porcelain, & Ceramic tile. Three giant buckets in, so far so good.

JazMan 01-30-2010 01:29 PM

Oh Boy! Strike 2. :no: Strike 3 if you bought pre-mixed grout. :yes:

Next time you should plan your project and ask question here. Do not ask for advice at those kind of places. You're not likely to get the right advice from those nice people. Most have no experience and do not hang around long enough to learn much. Plus, from whom would they learn?


Bud Cline 01-31-2010 11:56 AM

The non-experienced isle-walkers at the home centers push whatever products the company tells them to push. These are always the products with the highest profit potential hence premixed everything these days.

The premixed thinsets (really aren't even thinsets) and have many many issues, the same goes for the premixed grouts. Stay away from those products.:)

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