I am in the process of rebuilding a new ceramic shower stall. I am receiving mixed signals on using thin set versus mastic. I know the floor tiles must be set using thin set but what about the shower walls. I plan on using MasterBlend Thin Set Mortar mixed with Acrylic Mortar Admix for the floor. The ceiling was done using Acrylpro Mastic. The mastic container says it is also good for shower walls or any where there won’t be standing water. I do like the easy in using the premixed mastic over the thin set. I think the sticking ability of the mastic over the thin set will be a plus for installation of the wall tiles but I don’t want to cut corners and end up with another problem in a few years. What are some of your feelings? The walls are hardi board over felt tar paper.
Thanks,
Stuart Johnson
Red Oak, Texas
Replies
Please do not use mastic for anything other than a paperweight. I am having a hard thinking of any use for the stuff.
The problem with mastic is that it is water soluable. You can take a glop of mastic let it harden for a week, dump it in a bucket of water and it will instantly soften and be sticky. Expose it to too much moisture and it will liquify, e.g., re-emulsify.
It never belongs in a shower or in a bath or a kitchen, anywhere near water. I suppose you could use it for a completely dry location in a hallway, but good thinset is just as sticky and is far more permanent.
Thinset is very easy to mix in small batches.
I use Custom Building Products VersaBond at $15 a bag, which is way cheaper than mastic, too.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
I agree with Boris, mastic is virtually useless in my book. Mastic does not have a stronger bond then thinset, it has greater holding strength (i.e. keeping the tile from slipping down the wall) but a much weaker bond strength (i.e. keeping the tile from being pulled off or working loose). There are plenty of workarounds for the slipping issue, but once cured, a tile properly set in thinset isn't going anywhere. And, like Boris said, thinset is unaffected by moisture.
When I set tiles on a wall, I use my aluminum "L" shaped straightedge to act as a "bridge" for the first course. Then I can set tiles going up the wall without any slipping problems. After about an hour or so, I remove the "bridge" and can then set the tiles below my initial course. I use small pieces of masking tape to hold the tiles in place relative to the course above. Here's a pic of the "bridge":