Tile laid directly over gypcrete [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


View Full Version : Tile laid directly over gypcrete

03-04-2007, 09:00 AM
During our kitchen remodel the contractor removed our existing tile floor, thus exposing the gypcrete subfloor. Originally the gypcrete was covered in linoleum and the previous installers had put hardibacker over that with nails and laid tile. Once all this was removed there were lots of nail holes and large gouges in the gypcrete. In addition there is one area where you can feel the plywood subfloor flex and it makes a creaking noise when you step on it.

Having read this forum avidly, I know this is not an ideal substrate to tile over. I expressed my concern to the contractor, who assured me he has been doing this a very long time and it would be fine to fill all the craters with thinset and lay tile. I asked him if he would guarantee his work and he said yes. So I told him to do as he wishes as long as he is willing to redo it if there are issues.

So 18 X 18 porcelain tiles were laid yesterday directly over the cratered moonscape like gypcrete. They simply used modified thinset for porcelain to fill all the craters, backbuttered the tiles and down they went.

Today when I step on the tiles where the loose subfloor was, I hear that same sound....not surprising I guess. I may lack experience, but something tells me this tile job might not stand the test of time.

If anyone has any advice or input on how I should proceed with this situation I would appreciate it.

Thanks in advance,

Sponsored Links

03-04-2007, 09:28 AM
I wonder what he considers a "long time" to be??? A proper tile floor should NOT squeek or flex. No way around that fact. Be afraid...be Very afraid.

03-04-2007, 10:21 AM
This is a frightening prospect. To hear movement in a floor is bad...but to hear it over tile is even worse. I'm very cautious when going over any type of Gyp or lightweight concrete substraight. I usually prime in accordance with the gyp companies specs..often it is a non-cementicious product like Redgaurd, Ultraset, or a latex/acrylic bonding agent to lower the absorbtion of the gyp.

I follow that with Ditra or another membrane. I have never set directly to Gyp as it has so many issues with dust, porosity(it sucks the water and life out of thinset rapidly) and the reastion between the Cement in thinset and Gypsum is usually bad...They tend not to like each other from a bond perspective. So it's not likely to be a good marriage.

How large is this job? And how well do you know the contracter? He said he would stand behind his work...That's a good thing if you feel he'll step up to the plate if this becomes a problem...and it may not be realized as a problem for a year or longer.

03-04-2007, 11:15 AM
Thanks for the quick replies. The kitchen is quite small, 60 sq ft of tile total. The contractor is a really nice person who was referred by my wifes boss and through my recommendation has a job lined up with my boss. So, I think he will step up if there as a problem as his reputation is on the line. Unfortunately, I think he is just not familiar with gypcrete...his expertise is in cabinets and counters.

At the very minimum I think we need to fix the area where there is movement in the floor. How would one go about securing the subfloor better? Does the gypcrete need to be removed in that area so that additional screws can used on the plywood?

03-04-2007, 11:24 AM
We NEVER install tile directly over Gypcrete. We use a product called AFM (Anti-Fracture Membrane) First you roll on a primer then stick this matting over top. It allows movement of up to 1/2" which is HUGE! Stuff works great. We use it over gyp, concrete, wonderboard and more. Gives you that extra protection and piece of mind

03-04-2007, 08:11 PM
Just spoke to the contractor and he agreed to rip up the tile and do it over. Can
someone please give advice on how to do this job correctly.

First of all what is the best way to address the movement of the plywood subfloor under the gypcrete?

After that is resolved it is clear from previous responses that the gypcrete needs to be sealed.

What about all the craters in the floor? Does the floor need to be leveled before laying an antifracture membrane? If so, should it be leveled out with a self leveling compound or would thinset suffice?

Thanks in advance

03-13-2007, 10:06 PM
After hours of searching and reading threads I finally came to the following plan of action. First I drilled a large hole in the area in which the subfloor was loose and moving vertically. I inserted a coat hanger bent at a right angle and twisted it around until I found the nearest beam. I drilled a few holes through the gypcrete which were slightly larger than the head of some 2 1/2" screws. I drove a few of those into the beam and the floor feels solid now. Next I applied Level Quick Latex made by "Custom Building Products". After numerous phone calls I was able to track down some Ardex GS-4 self leveler for gypcrete floors. 1 1/2 bags of this leveled the floor out nicely. Here is a photo with of the leveling half done, so you can also see how bad the floor was
Ideally I would have used Ditra over this, but I didn't have time to wait for mail order as I don't know any retailer that sells it locally. People also speak highly of protecto wrap, but that was the same situation. Several posts said Dal Tile's CIM 500 membrane was the same as Protecto Wrap and that was available locally, so that's what I wound up using. The CIM 500 came with it's own primer which was nice. I applied that and 1 hr later stuck the adhesive membrane down.

More photos can be found athttp://www.flickr.com/photos/parkerman/sets/72157594181067250/

This forum has been such an incredible help in all my tiling projects :tup2: . Hopefully this thread might aid others like myself struggling with the headaches of gypcrete floors. Thanks to all for your generous advice.

03-13-2007, 10:21 PM
Hi Parkerman, did you use a primer before you put that SLC down? Also with all those nailholes in the gyp, isn't there heat tube in it? If so I hope they didn't poke any holes it them.

03-13-2007, 10:47 PM
Yes Musky Mike,

As mentioned I used Level Quick latex primer by CBP prior to pouring the Ardex GS-4. Fortunately there are no heat tubes in our floor. It's just a thick bed of gypcrete. Fortunately, we have not experienced much cracking. The previous tile install used hardibacker and secured it down with nails. There were lot's of nail holes in the floor, but no cracks believe it not.

Tool Guy - Kg
03-13-2007, 11:10 PM
I was thinking the same thing as Musky as I saw those pics. Glad you used a primer. :)

03-14-2007, 07:51 AM
The CBP primer said it was suitable for porous concrete, which I assumed to be the same as gypcrete. Of course Ardex recommended to use their primer, but I could not find it. Hopefully any latex based primer will do the job.

Hard to believe the contractor tiled right on top of that floor thinking it would be OK. Not surprising he was able to pull up all the tiles without breaking one. The residual thinset came up with a putty knife.

Thanks to this board I have a lot more confidence in the way it is done now. The big test will be when they move the stove and fridge back in