Tile Over Gypcrete

Golden Rule

I have yet to lay tile directly over gypcrete, but I come across a HO who had laid tile over gyp shortly after it was poured. The house is an engineered log home. She has lots of cracks in her 12" x 12" ceramic tile. I am assuming they are primarily caused by settling, but I am wondering if any of you have had problems putting tile over gyp. Her floor joists are BCI's i would assume, but I can't verify whether or not they used bridging. I don't plan to replace to tile but i am wondering if structural settling translates more drasticly through gyp to tile vs other forms of tile backing. Thanks.

kevjob

gyp is not an approved sub strate for tiling even ditra won't help there. Backers are for uncoupling not strength.

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Kevin
Basement Finishing Highlands Ranch Colorado
Littleton Colorado, Basement Remodeling
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Golden Rule

Thanks. That was what I was thinking. I listed the framing info because I know poorly framed floors are bouncy and bad for tile. Thanks tho exactly what I was looking for.

jfman

So what can you put on top of the gycrete to make it suitable for tiling?

Heritage

Is there hydronic radiant heating in the floor?

If there is, it might be an issue with the sleeper. I remember a house that had the same problem, but with 24 x 24 Porcelain tiles. Differential cracks all along...and we're talking around 3000 sq/ft of main floor tiles. All over the place. We removed one of the tiles to see how it was installed...the installer was actually very good, back buttered, full coverage...everything was nice.

It was a problem with the gypcrete/sleeper. It's gotta be mixed right, can't be too thick and then you gotta worry about the bond with the sleepers, how it reacts to shrinking/expanding of the subfloor/sleepers and a sleu of other issues.

If I recall correctly, our solution was to rip it all out and have a do-over, this time NOT using Gypcrete. Once we submitted our bid the HO decided they will live with the cracks (after all, this was a 2 year old custom house). Shame really...but it taught me one thing...use Gypcrete with extreme caution/if at all.

Sorry I don't have a solution...if I was in your shoes I would do what I did back then...call my best tile guy out and have him diagnose the issue. Removing one tile for a little investigation would be a good start.

They also have additives/prep mixtures you can use before laying the tile...might want to look into that also.

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Mike Finley

Cracks in the tile itself or in the grout joints?

You can certainly set tile over gypcrete with the right preparations. Mapei makes a couple of products you can apply to the gypcrete before tile install, and of course Ditra would work great.

The basic problem with gypcrete is it's got a portion of gypsum in it instead of all concrete (which gives it it's benefits of being lighter than concrete and more sound deadening), but the gypsum will deteriorate with moisture so tile set directly to it is in risk of having the bond degrade over time. If you use that Mapei product or put Ditra over it you are waterproofing the gypsum.

If the woman's floor isn't structurally sound enough for tile then it doesn't matter what you waterproof it with, it won't solve the problem.

Bud Cline

Maxxon Corporation owners of Gypcrete offer specific instructions for installing tile over their product. I'm surprised no one has thought of contacting Gypcrete before now.

They will tell you that an application of Noble's CIS is an approved method to prepare the product for a tile installation. I'm thinking I also read where Schluter's DITRA is also acceptable, and YES Mapei also offers a solution.

Gypcrete is notorious for cracking within itself and it isn't easy to bond tile to as far as a tile-for-tile application is concerned, hence the use of an isolation membrane to bond the tile to.

Bridging of the floor joists has little to do with it. The type of floor joists has little to do with it. No matter what is used in the floors structure there is still deflection minimums that must be met. Gypcrete will only meet those minimums if the structure does.

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