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Janet 07-29-2008 04:55 PM

Laying Porcelain Tiles Over Gypcrete @ Lino
Hi all. I've just moved into a condo and I'm hoping to get some advice vis a vis the proper procedure for laying porcelain tiles in instance: a) over (what I'm told is) gypcrete and; b) lino. I'm also having some issues about whether to tile underneath the built-in dishwasher (booooo!) or simply to the 'apron' of it (yeahhhhhh!). There are a lot of conflicting opinions about the dishwasher thing.

After doing tons of research on the web, I've come to the conclusion that gypcrete is a nasty, nasty word in the trades but I'm still not sure why? Is it because tiles won't adhere well, and/or the gypcrete will expand and contract more with change and temperature/humidity than the tile and/or the gypcrete sucks up too much water and the mortar can't properly cure. I'm well acquainted with what a DITRA mat is (I have a sample of it in front of me) but still not clear of its exact utility (despite having read and re-read the literature).

Would a polymer enhanced mortar negate the need for a DITRA mat?

I will also add that I have a particleboard subfloor over which the gypcrete (1") has been poured ....and the areas that I want to tile are very small.

Any help is seriously appreciated...this thing is driving me crazy!!!!!! I'm not attempting to do this myself, but I want to make sure that whoever does...does a good job. I've already hand one person (friend of a friend) suggest using 'topical' concrete?

angus242 07-29-2008 05:39 PM

The problem with gypcrete is it doesn't want to stay adhered. So if you want to put any kind of flooring on it that needs to adhere as well, chances are high that the flooring will pull up the gypcrete. I would not adhere anything to it. I'm not aware of any product that you can adhere to it. Maybe start considering a floating floor of some kind.

Janet 07-29-2008 06:43 PM

Gypcrete Gymnastics - Jumping Through Hoops!
Thanks for the response Angus...I'm really 'at sea' here. The prior surface was lino, and it was a ***** to get off---->It took a lot of effort to wet and scrape off the paper backing; the lino had been glued on (and was likely ultra cheap builders grade stuff--->or was the glue simply necessary for the gypcrete?)

And kindly bear with me as I try to understand this, if the problem with gypcrete is adhesion, do you mean adhesion of the gypcrete to the particle board sub-floor or adhesion of tiles to the gypcrete---->or is it both?

And...if you woud be so kind to provide it, what is your opinion of using a Ditra mat? If tiles don't adhere to gypcrete, why would a Ditra mat? Schluter's specs recommend un-modified thin set on both bottom and top. I understand how the tiles would stick to the top of a Ditra mat, but not how the mat iteself would adhere to the gypcrete?

Thanks in advance....Janet

AtlanticWBConst. 07-29-2008 07:12 PM

Do not use thinset with gypcrete. The chemicals in each react with eachother. I had this conversation with my tile supplier about two months ago. It is something that is known and clearly understood in the tile industry.

You can use the membrane, but I do not recall with which adhesive or mortar. Maybe Bud Cline will know. Your local tile supplier would also know (and I am certainly not talking about the stooges at the Big Home Improvement Stores)

angus242 07-29-2008 07:20 PM


The problem is gypcrete doesn't like to stay adhered. Actually, it likes to crack or crumble. You can see the problem with adhering anything on top of it. I know that people use Ditra directly over the gypcrete but that's something I would still try to talk a customer out of. I just don't trust the gypcrete. IF you are going to tile, Ditra is your best option. Still, I may look into other floating floor options before deciding on tile.

The unmodified/modified thinset issue has to do with curing times. Technically you can use modified under Ditra that's placed over a cement-based substrate but the drying time is days if not longer. This is why they want you to use unmodified. I use Kerabond for Ditra installs when unmodified is called for. Never had an issue with it.

Did I mention looking into a floating floor? :whistling2:

Janet 07-29-2008 07:47 PM

Might you kindly define a floating floor? And what kind of elevation that might incur? I have built in cupboards. And still wondering about the dishwasher...but now I'm getting to be a pushy pants.

Ohhh.:no:...and since I'm really, really going out of my way to alienate myself from advice by being such a pushy pants...any advice on what I should look for in a tiling contractor?

Bud Cline 07-29-2008 08:06 PM

Janet Gypcrete has been problematic since the beginning. The industry is full of Gypcrete horror stories. It is primarily the gypsum in the Gypcrete that is the issue. Gypsum and tile-setting products don't go together unfortunately.

Gypcrete is a product of the Maxxon Company and they can make recommendations for installing tile over their lovely product.

They will tell you that a product called CIS from the Noble Company is the answer. Noble CIS is a 30 or 40 mil vinyl like sheet membrane with a fabric attached to both sides. The CIS is attached to the Gypcrete using thinset and then the tile can be applied directly to the CIS. CIS is also a waterproof membrane.

I don't know if Maxxon is also recommending DITRA or not. DITRA is a great product but to maintain any warranty's (and they won't be much) I would get the information from Maxxon and follow their suggestions.

Here's another red flag in your case.

You keep saying the Gypcrete is installed over particle board. I certainly hope you are mistaken. Maybe OSB (oriented strand board) but never particleboard. If it turns out it is particle board then I would strongly recommend you do whatever is necessary to waterproof that substrate to keep water from one day getting to the particle board in the event of some kind of a leak. That would include flashing up the walls a few inches. Also keep your homeowners premiums paid.:)

It's not that "nothing" sticks to Gypcrete it is that nothing tile-related sticks to Gypcrete very aggressively. Gypcrete doesn't like moisture and tile needs moisture to be installed properly.:)

angus242 07-29-2008 08:22 PM

A floating floor is just that; floats over the substrate and is not mechanically fastened down.
Since you:
a) want tile
b) possibly have particle board
c) if b, then moisture issue abound....

look into this product. As best I can tell, it gives you answers to your problems:

Bud Cline 07-29-2008 09:23 PM

Now there's an excellent idea!


Where are you Janet? (geographically)

Janet 07-30-2008 09:33 AM

Gentlemen...many, many thanx for your input. I say particleboard because I know what plywood looks like and it's not that. I noticed strands in it so it's most likely the OSB you mentioned (I am a girl after all):eek:.

I'm in Edmonton, Alberta, Canada...latitude 55 so I'm relatively far north.

What about using modified thin set directly over the gypcrete? It's supposed to help it adhere.

What about laying porcelain over lino?

Aside: I just got off the phone with 'Manwell' who pours concrete and lays tile--->he claims to use regular mortar!?!?

Again, thanks for your help

angus242 07-30-2008 09:50 AM just had 3 guys tell you tile directly over the gypcrete is a BAD idea. :no:

You need to membrane over the gypcrete to tile......period. :yes:

I still have my vote for a floating floor. Do a little research on SnapStone before you rule it out. It's real porcelain tile and doesn't need thinset. :whistling2:

Bud Cline 07-30-2008 04:38 PM

SnapStone is being sold in all of the southern corridor Home Depots across Canada. SnapStone is a high quality porcelain tile floating floor system that requires no adhesive what-so-ever.:)

Don't try to convince any of us here :no:that tile can be installed directly to Gypcrete because it can not. Period. :no:

Be careful with this "Manwell" he obviously doesn't know what he's talking about when it comes to this subject.:no:

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