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Ditra Questions

6K views 9 replies 2 participants last post by  JazMan 
#1 ·
So I am using Ditra for the first time. I am putting it over plywood underlayment which I have covered with self leveling compound. I will then be placing 16 inch marble tiles over the Ditra. My questions are:

1) I am confused about what type of thinset to use to set the Ditra. Do I want to use modified or unmodified to bond the Ditra to the SLC covering the plywood?

2) Am I correct that I should use perimeter joints around the perimeter of the room? Which should I use?

Thanks!
 
#2 ·
Hi Winds,

Before we go on to the thinset, you need to confirm that the subfloor system is stiff enough for marble tiles. I have this hunch...........:huh:

Tell us the size of the joists, the spacing and the unsupported span. If at all possible figure out their species and grade. There should be grade markings on them. Then tell us about the subfloor and what ever is over the subfloor. Your location might help too along with the age of the house.

If the entire floor is covered with SLC, Schluter wants you to use a high quality unmodified thinset to install Ditra. Any color. Install the tiles with high quality white unmodified.

Perimeter joints, you mean leave a space? Always leave at least a ¼" of ungrouted space between the tiles and any solid object.

What kinda room is this, size?

Jaz
 
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#3 ·
JazMan-I appreciate your input. From the number of posts you have looks like you know what you are talking about. I don't have the exact floor specs in front of me but I did work with a professional tile installer and we figured deflection, crawl under the house and looked at the joists, etc. and we were well within the appropriate stiffness for marble. I have 2 layers of flooring over the joists with the top layer being 3/4" underlayment grade plywood. There is a very small unsupported span (I think it was about 10 feet) and the room is small--only about 80 square feet.

I thought you should use unmodified thinset beneath the ditra but while doing my checking and double checking I found some conflicting recommendations. I think part of the confusion is that some people have said you use one thing over plywood but another over cement---I have SLC over plywood so I assume that is effectively the same as cement?

Regardless, sounds like you have solved the issue for me--I will be using UNmodified thinset to set the ditra and then the same UNmodified thinset (white only) to install the tiles.

What I was talking about with the perimeter joints is that I saw a video from Schluter on YouTube and they have what appears to be a plastic strip they are putting down around the perimeter over top the ditra before installing tiles. I hadn't seen this before and hadn't planned on using it. I am going to be putting base and shoe around the room so there is no need for me to get a tight fit with the walls. I am assuming since I will be using base and shoe that I don't need to worry about the strips and instead just need to make sure I don't wedge the tiles into the wall too tight.

Thank you very much for your assistance. Any further help you can provide me during this project is greatly appreciated.
 
#4 ·
Not sure if this question should go into a new thread or not but I would like people's opinion on whether or not I should use diamond mesh or something like Mapei's Mapelath with the SLC. I did not use it on the very small room I did (hope that is all right) but I will be doing a slightly large room that is in total about 200 square feet, installing the same marble tile. I need to level that floor also and was wondering if I should use a mesh.

Would you guys recommend a diamond mesh for a 200 square foot room I am using SLC on? If so, what kind should I get? Is the Mapei synthetic Mapelath good? All my other products are Mapei so I was considering using the Mapelath if I do in fact need a mesh.
 
#5 ·
So when I bought my tile I worked with the owner of a very reputable tile shop. He sold me everything for the project...tile, ditra, thinset for ditra, thinset for tile, etc. I just looked at what he sent me. I have:

Mapei Kerabond (Tile Mortar) which is white
and
Mapei Ultraflex 2 (Tile Mortar with Polymer) which is also white

The Ultraflex 2 is modified, right? Are you guys saying that I shouldn't be using the Ultraflex 2 for the setting the ditra OR the tiles?

Thanks!
 
#6 ·
In regards to the SLC and mesh; choose the SLC and follow the directions for that system.

If you did the calculations for the joists' deflection, then I will take your word for it. Do you recall what the deflection was and for what loads? The size of the room is not relevant, but good to know.

Two layers of sheathing is required for natural stone in addition to a membrane or concrete backer, so you should be good with that too.

Schluter recommends unmod on SLC, the ply under it is not relevant. And they always want unmod to set the tiles. What specific one will you be using? I ask cuz premium unmods are not easy to find sometimes.

Winds said:
Regardless, sounds like you have solved the issue for me--I will be using UNmodified thinset to set the ditra and then the same UNmodified thinset (white only) to install the tiles.
Perfect.

As for the perimeter moldings; You don't need those.

Jaz
 
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#7 ·
JazMan-What are your thoughts (or those of anyone else) on the thinsets that I already have (the Kerabond and Ultraflex 2 I listed above)? Are those useful for my needs? If not, I would much rather waste them and get the best....don't want to go through all this trouble and then have an issue trying to save $30. Thanks!
 
#8 ·
Kerabond is a premium unmodified mortar and is considered one of the best. However, because you are installing heavy natural stone tiles, I recommend a medium bed mortar. They are formulated to help prevent drooping and sagging. Kerabond T is the Mapei product that meets this criteria. My favorite is Ditraset, but may not be available where you are. Ditraset is unmodified and would be perfect for both steps of your project as described.

Or, keep the Ultraflex 2 and use it under the Ditra. Yes Schluter says to use unmod, but it'll work just fine. Might even bond better than unmod since modified have more stickum power to them.

So, you could go several ways but it depends on whether you can get Kerabond T or Ditraset. Let us know for more clarification.

Jaz
 
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#9 ·
I found Ditraset at a tile store in a nearby city today so went and got some. I will plan to use Ditraset to set the ditra and then to set the tiles over top the Ditra.

Thanks for the recommendation!

With regards to the SLC, my self leveling compound (from Mapei) "recommends" using "Mapelath" with it (instead of diamond mesh). Am I correct in implying from the response above that there are SLC's that do NOT recommend using a diamond mesh? It would be easier at this point to change to a SLC that does not need the mesh/Mapelath than to get that and use it....assuming another product is just as good without the mesh underneath. Any recommendations on SLC to use?
 
#10 ·
SLC over plywood or OSB requires the lath. If you need to do the entire floor you don't have much of a choice. Also plan on it being thicker than you may have first thought it will need to be.

Jaz
 
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