Porcelain tile separating from gypcrete slab
We recently had our kitchen renovated/enlarged and had radiant heating installed in a gypcrete slab. The floor is one story up over a new basement space and sits on 3/4 inch plywood on properly supported floor joists. Shortly after the kitchen was completed, we began to hear loud cracking noises coming from the kitchen floor and eventually realized that the 18×18 porcelain tiles were separating from the gypcrete. The result was that we had most of the tiles pulled up and reset and that seems to have solved the problem. Standard thinset was used and it looked like most of the thinset was still attached to the tile when it was removed. Why did this happen? The footings of the kitchen addition sit on the granite schist and are secured with rebar so there is no movement there.
Replies
A couple questions
was the floor heat "on" during or shortly after the tile was set?
how long after gyp installed was the tile set?
were the tiles buttered with thin set?
how long have the replaced tiles been down?
A couple?
Ok, 4
Discussion of this situation on the board might put forth information for others to avoid this problem.
no?
Answers to a couple of questions
The heat was not on for a few weeks. The furnace and radiant heat system were not installed yet. The tiles were laid in thinset that had been spread on the slab. I can't remember how long after the gypcrete was poured, the tiles were laid but it might have only been a few days. The new tiles have been down for a few months and seem to be secure.
Short answer: bond broke.
So you already had your problem solved by having your tiles reset. Why are you interested in speculation ('cause that's all you're going to get here) vs. simply solving your problem and moving on. If its still a lingering question then it seems like the person(s) who did your renovation would be the best party to ask.
Bond broke
my contractor said had had no idea why this happened and I was curious to see if any one else had a problem like this.
Was the contractor that repaired your tile problem the same contractor that created it in the first place?
Clearly it's some combination of bond failure and differential movement.
My money would be a little on the side of bond failure being the main culprit. I suspect that there was some efflorescence on the surface of the gypcrete and this prevented the thinset from bonding very well. Reading up a little on gypcrete it appears that improper mixing could cause efflorescence to be worse than normal, and likely various site conditions could contribute to this as well. One might wish to guard against this on newly-poured gypcrete by giving it an acid wash before using thinset. Or perhaps using some sort of modified thinset would be appropriate.
But the conditions present offered plenty of opportunity for differential movement as well.
Sounds like a job where a decoupling membrane would have been appropriate. Ditra would have been my choice.
Same contractor
same contractor, different tile guy.
Tile on gypcrete, not recommended...
Get in touch with Maxxon tech and see what they have to say about their product.
It's poor form to tile directly to gypcrete. Thinset and gypcrete do not play well together, especially when it's a direct tile-to-gypcrete installation over RFH. The gyprete isn't strong enough to handle any stresses put on it by differential movement. An intermediary like a membrane used between the two makes things go better.
The following info may be outdated, thus the recommendation to get in touch wth Maxxon's tech department. But they used to recommend a product called Maxxon Overspray, it acted like a primer/sealer. Then an anti-fracture membrane over that. Then tile on the membrane.
Hope you get things resolved.