Mastic vs Thinset in shower...

goddiJuly 25, 2008

I just read the following in the This Old House e-zine concering tiling above a tub:

"Ferrante glued the tiles to the backer board with latex tile mastic, not thinset mortar." Gee Whiz...I thought using mastic, as opposed to thinset, in the shower was a BIG NO-NO. Can anyone explain why this recommendation to use mastic in the shower is valid? I goes contrary to everything I have read on this and other Forums. From what I understand, Mastic is the premixed stuff in a tub and Thinset mortar is a powder prepared by just adding water, and that only Thinset should be used in the shower wall area.

Thanks... Gary

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kgwlisa

It's NOT valid. It's a lesson in "don't believe everything you read." Although it would seem to me that using a water soluble adhesive in someplace that will be taking a lot of water seems like a dumb idea, but what do I know? :)

    Bookmark   July 25, 2008 at 10:54AM
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toadangel

maybe it was above a tub-only install, not a shower? still probably not a great idea, but it's hard to tell without the original context.

    Bookmark   July 25, 2008 at 1:35PM
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goddi

In the TOH article, they have an Overview slide that shows the shower supply pipe. One of the things that I don't understand is that they say to put a skim-coat of thinset first...then use the mastic to apply the tiles. I don't see how a skim-coat of thinset would remove the problems created by using mastic to set the tiles.
Gary

    Bookmark   July 25, 2008 at 1:46PM
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peteinsonj

The problem is that even if the work was done correctly (using thinset) -- who knows who wrote and edited the copy?

I seriously doubt it was the installer!

I used those terms interchangeably for a long time, since I used mastic on many DIY project like tables, backsplashes, etc.

Then I moved into THIS house. And had 2 of the 3 baths fail... because someone used MASTIC, not thinset.

Now I'm a stickler for using the right words!

    Bookmark   July 25, 2008 at 4:04PM
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goddi

Here's the full text:
"For the project shown here, we enlisted the help of tile contractor Joe Ferrante, who has been laying tile for This Old House projects since 1986. The first and most important step, insists Ferrante, is to start with a clean, stable substrate. He then fills the backer board seams with thinset mortar and embeds fiberglass-mesh joint tape int he mortar. Finally, to ensure a strong, long-lasting bond for the new tiles, Ferrante goes one step further and trowels thinset mortar over the entire wall.
For this installation, Ferrante used 4¼-inch-square ceramic tiles,the most common and easiest-to-install bath tiles. However, the methods shown here work on any wall tiles, including stone and glass. Ferrante glued the tiles to the backer board with latex tile mastic, not thinset mortar. Mastic is much stickier than mortar, so you won't have to worry about the tiles sliding down the wall."
Gary

    Bookmark   July 25, 2008 at 4:49PM
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bill_vincent

The only thing I can think of is it was an old show. Joe Ferrante died in 2007 on the way to the hospital after suffering a heat attack on site of a This Old House project. Back in the 80's and early 90's it was widely acceptable to use mastic for wet areas. Matter of fact, most commercial work is STILL done with mastic in wet areas, even though it's strongly discouraged. What happens is the mastic can soften back up from moisture hitting it, and once it does, that's the end of any kind of bond to the tile. After that, the only thing holding it place is the grout.

    Bookmark   July 25, 2008 at 5:37PM
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goddi

Bill, Yes, I knew he had died. But what a boner for TOH to print this. Some months ago, a contractor I had hired to do our bathroom renovations used mastic in the shower. I discovered this. He said he had done it 1,000's of times. I fired him and stripped all the new tile and durock down to the studs and started over...
Gary

    Bookmark   July 25, 2008 at 6:03PM
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bill_vincent

Best thing you could've done.

    Bookmark   July 25, 2008 at 7:00PM
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mongoct

I used to even think that telling people to refer to the manufacturer's installation instructions was a safe bet.

Until I read one tile manufacturer's recommendation to coat their glass tile with mineral or baby oil prior to grouting so that the oil would act as a grout release.

When I contacted them, their reply? "Do you think that's why we've had so many complaints about blotchy and uneven grout color grout with our glass tile?"

Supposedly they are going to rewrite their online pdf instructions.

Mongo

    Bookmark   July 27, 2008 at 1:11AM
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tom_p_pa

I saw two episodes in this old house where they used "thinset" (mastic in disguise) in the premixed tub. And another episode where they used a copper shower pan with no preslope. It was a beautiful pan, with soldered corners too. I think the moral of the story is that because you see it on this old house, it is not necessarily correct. And the manufacturers of tub "thinset" mastic say it is fine for in the shower use, and some advertise it has special mold inhibiters.

    Bookmark   July 27, 2008 at 11:48AM
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bill_vincent

Two things I want to say here, one in defense, and the other as a criticsim.

In their defense, I already talked about the mastic. Additionally, the whole thing about preslope only started about 8 years ago, and even now, here in New England, copper pans are still installed alot. That doesn't make it right, though.

In criticism, I'll say this-- I've been in tile literally all my life. My father and grandfather was both tile contractors, and I've always been around it. Since the early 70's when Bob Vila first appeared on PBS, I've watched shows whenever they've been on about setting tile. We're talking a span of almost 40 years, and during that time, I've yet to see a SINGLE SHOW, where the tile was installed properly from start to finish. Even the champion of the downtrodden, Holmes on Homes-- he's got alot to learn about tile setting too!!

    Bookmark   July 27, 2008 at 12:15PM
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MariposaTraicionera

Mongo, thanks for your post. I was told to check what the manufacturer recommended using, and of course they said "mastic." Seems like the tile stores (many of them) go by what the manufacturer say. I will ignore the "mastic" on my installation.

Good luck Goddi.

Mari

    Bookmark   July 27, 2008 at 1:11PM
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gbsim1

I recently had to start over with a total shower tearout (again) because mastic was used to adhere the wall tiles over Kerdi. I removed most of the tiles within a week, but a few cut ones I didn't bother with trying to save..... almost a MONTH later even with no grout and a fairly wide spacing the mastic was still as wet as when it was put up.

    Bookmark   July 27, 2008 at 1:56PM
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bratty33

Help!I just finished putting tile in my shower,under the guidance of a 'pro' I used mastic(even on the floors) ...now i am PISSED.I want this done right,I dont want tiles popping off in 5 years(or 6 months!)So, any advice how to get the tiles off without breaking them?Also,the tiles I have gotten off are taking a skim of the hardie backer with them...do i need to replace that as well?Last but not least...the 'pro' built the shower pan..after his first bad advice I started doing more research and asking detailed questions...apparently he didnt protect the weep holes before putting in the deck mud...can i carefully chip out just around the drain,protect the holes and re-pour??? Or do i have to demo the whole damn thing and start over??Thanx-Cheri

    Bookmark   July 27, 2008 at 5:04PM
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bill_vincent

I started doing more research and asking detailed questions...apparently he didnt protect the weep holes before putting in the deck mud...can i carefully chip out just around the drain,protect the holes and re-pour???

I almost hate to ask this, but in your reasearch, have you run across a term called "preslope", and did your installer put down a mortar slope BEFORE your pan membrane went in?

    Bookmark   July 27, 2008 at 5:44PM
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bratty33

yes,he did that step...however, he did not put any wire mesh in any of the mortar in the pan...is that a must?

    Bookmark   July 27, 2008 at 8:56PM
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bill_vincent

No, it's not. In answer to your question, yes, you can just remove the center and replace it after clearing and putting some gravel around the weepholes.

As for the Hardieboard, if it's lost its strength, then yes, you should replace it. If not, you should be okay to go over it. As for removing the tiles, it might help to put a humidifier in there overnight.

    Bookmark   July 27, 2008 at 9:05PM
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bratty33

thanx--I will let you know how it goes!

    Bookmark   July 28, 2008 at 2:19AM
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