Need help with installing Ditra [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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10-05-2006, 03:56 PM
Hi everyone. I recently bought a condo and want to replace the vinyl floors with ceramic tile. Unfortunately, the subfloor is gypcrete and cannot be removed per the condo board. Lowe's and HD Installation Services recommend placing a quarter inch Hardi-board over the gypcrete and then putting the ceramic tile on the Hardi-board. Will this work in the long run? Does anyone have experience using Hardi-board on gypcrete? Please help - this is starting to get confusing and scary.

Thanks in advance,
Mt. Pleasant, SC

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10-05-2006, 04:03 PM
Nope, don't think that will work. Go over to and read the installation instructions for DItra. You may be able to use that, not sure.

Another possibility is maybe EasyMat from (you can get to either of these from icons on the site.

John Bridge
10-05-2006, 04:59 PM
Welcome aboard, Raj. :)

I agree with Jim. Your only hope is a membrane. None of the boards are specified for over lightweight. :)

10-05-2006, 05:03 PM
The backerboards must be set over a layer of wet thinset mortar and then screwed down. You can't drive screws into the gypcrete. That's why the backerboards are out.

The membranes are just adhered to the floor with thinset mortar, so that is possible over the gypcrete.

10-05-2006, 05:57 PM

We just finished a condo that had the same rules. If the gypcrete is old and if the existing floor is glued down you may have problem areas to repair before installing the ditra. If the floor is sound and in decent shape just follow the installation instructions and it should go well.

HD carries ditra by special order and it costs about $3 a foot. You can order it online for about half of that.

10-05-2006, 06:01 PM
Make sure you know if the condo association requires sound isolation membrane. It is required in quite a few condo's now days when hard goods are set on the floor.
Good Luck

10-05-2006, 08:45 PM
If you need sound deadening...the EasyMat would probably work if you go with the thickness specified for that purpose. Double-check if it is allowed over gypcrete first, though.

10-06-2006, 07:32 AM
OK thanks. Looks like Ditra is the way to go. No sound reduction needed according to the condo rules.

10-06-2006, 08:37 AM
Hi everyone. I will be using Ditra in order to install tile on a gypcrete floor. I am not a very technical person and this is getting complicated but I think I should try to learn how this is done in order to make sure the installation is done right.

I've been reading other posts and this is the best step-by-step I can figure out but I still have some questions especially Step 2 below.

If something is wrong, out of order, or missing, please let me know. Thanks.

Step 1: Make sure gypcrete floor is clean and use gypsum based leveling compound instead of cement based leveling compound. If there are cracks in the floor, do these need additional repair or is leveling compound all that is needed? I am nor sure about this.

Step 2: I am not sure if I need to use something to seal the gypcrete. I do not have radiant heated floor. This floor is 7 years old and I don't know the builder or manufacturer. If the gypcrete needs to be sealed, what should I use?

Step 3: Follow instructions on Schluter website on how to install Ditra. Use Mapei kerabond grey color mortar to make sure Ditra is adhering properly to the Gypcrete. Use Kerdi for waterproofing.


10-06-2006, 05:19 PM
Everytime I have installed over gypcrete I have used a troweled on membrane to seperate the thinset from the gypcrete. I have been told gypcrete re-emulsifies(I never have tested that though). Around here the wood floors are floating and the tile is set over a membrane-not ditra due to the moisture from the thinset. The stuff I have used has been supplied so I am having a hrd time remembering the name. I'll post when I remember. Seeme it was made by hydroment though.

10-06-2006, 05:23 PM
Don't know on the other things, but if you want the floor to be waterproof, it will be easier to use Kerdi-band on the seams rather than Kerdi, since it is thinner and easier to work with. The next question is, 'why do you want to the floor waterproof?'; that's not normally needed. Unless you do stuff at the edges, whatever is on the floor will spread to the edges, and go in there.

10-06-2006, 05:47 PM
Try this. It has some specific instructions and guidance.\&LANG=en&user=dis&lang=en

10-06-2006, 05:50 PM
Yeah, gypcrete re-emulsifies talcum powder..i hate gypcrete. :bow: It is considered sound proofing,also, and needs to be primed.Mark's link has it covered :tup1:

10-06-2006, 07:24 PM
Welcome, Raj. :)

Please don't start a new thread with each new question. As you can see, folks were still answering you gypcrete questions on the previous thread when you started this one. Gets confusing. Just bookmark this thread so you can always find it again.

1. I dunno. I have no experience with gypcrete floors.

2. You're usually counseled to follow the gypcrete manufacturer's instructions for sealing the stuff, buy you clearly can't do that. Some manufacturers of setting products, such as the one for Custom that Mark posted, will have guidelines for sealers or primers for use with their products.

3. Schluter, unfortunately, just indicates you should follow the gypcrete manufacturer's guidelines for sealing and then install their product with a dry-set mortar. I honestly don't know what the gypcrete people usually recommend. We have people hereabouts who will know, though.

My opinion; worth price charged.

10-06-2006, 07:42 PM
I also have a gypcrete floor to tile. My floor will have water radiant heat. I have been reading as much as I can about ditra as I havenít used it before. It is interesting after reading customs instructions for redguard over gypcrete that they recommend their top of the line modified mortar. That just confuses me. Not that it is wrong just that it is different that what dirta recommends. Iíll be watching this thread for any good info anyone has about the subject.

10-06-2006, 09:32 PM
After painting on the RedGard, you've isolated the gypcrete from the thinset, so you can use whatever you want (course another membrane would be a problem).

10-07-2006, 12:17 AM
The water in thinset is nowhere near enough to cause a problem installing Ditra. Even if it were, the latex primer you use first fixes that.
If you were to use Redgard, it requires a 4:1 water to Redgard primer first. That is far, far more water than in thinset. I do quite a bit of tile over hydronic radiant, & I strongly suggest you guys step up to a true sheet membrane like Ditra or Nobleseal. The liquid membranes like Redgard are good products, but they're not in the same class as the true sheet underlayments.
Raj on questions 1 & 2, make sure not to put anything down at all, not even patching compound, until you've cleaned & sealed it first. Maxxon Overspray is one sealer you can use (diluted per the instructions). I also use acrylic admix diluted.

10-07-2006, 10:16 AM
Thanks for the advice everyone :clap1:

Okay, here is Version 2 of the tile installation with a couple of additional questions.

Step 1: Make sure the gypcrete surface is clean and dust-free.

On some of the gypcrete, there is a very thin layer of a light yellow substance - possibly dried adhesive residue from the previous peel and stick vinyl. Does this need to be removed? If so, what can I use to remove this?

Step 2: Seal the gypcrete using Maxxon Overspray diluted per instructions.

Where can I get Maxxon Overspray - I'm guessing Dal-Tile would have it. An alternative is using diluted acrylic admix - what is the dilution ratio for this?

Step 3: Make sure floor is level - use gypsum based leveling compound instead of cement based.

Step 4: Use Ditra sheet membrane per instructions. Use unmodified thin set per Ditra instructions - Mapei kerabond grey color has been suggested in other posts. If an area needs waterproofing (bathroom or kitchen), use Kerdi-Band also per instructions.