Usually, we don't. I've never used Ditraset, but I'm told it's a terrific product. One thing you need to realise-- Ditra Set is an unmodified thinset, and as far as being able to resist a direct impact, it wouldn't do very well, as you've seen. However, as a bonding material, it does the job it's supposed to.

For a Kerdi installation, there is nothing better. Trust this...it works quite well.

Thanks for the explanation and the confidence.

Since Ditra-Set is light colored when wet and dries fairly white, I assume not seeing the Kerdi color change that Mongo shows in his "how-to" is ok?

Thoughts after putting up my first piece of Kerdi:

Mixed my thinset so it looked as much like the example Mongo showed as possible. Dripped some, but not too much getting the thinset on the wall. I did burning in and flat troweling as two steps. After flat troweling I combed with the 1/4" X 3/16" V notched trowel. All looked quite even.

Patted the center in place and then the sides and then started with the 4" spatula. Seemed like this step could go on as long as one wanted it to. I would think I was finished and check the entire sheet and find it was a little uneven - so more work with the spatula. Bill, do you make more than one pass with a spatula when you are putting up a piece of Kerdi? I am guessing the thing might be to come up with consistent pressure and a consistent way of working from the center to the side.

I think before I put up any more Kerdi I will go buy some dark unmodified thinset. Seems like it would be a big advantage to be able to see whether all the thinset is in contact with the Kerdi.

Edwena

Hmmm.

When I hang Kerdi, it goes relatively quick. I've never watched the clock to get a "minutes per sheet" thing, though.

I usually use gray thinset, simply because it's less expensive. Somewhere along the way I must have used white, though.

Once you hang the sheet, pat it with your hands and get on it with the trowel or knife. The idea is to embed the fleece in the thinset, not move the thinset around behind the Kerdi. So use a low blade angle (handle of the knife close to the wall.

A high blade angle (hand away from the wall) could move thinset around behind the Kerdi and could give you an uneven surface.

Best, Mongo

Thanks Mongo

That is exactly what I am doing - moving the thinset. That's why I thought the process could go on forever, I just kept pushing thinset out the side. The sheet I put up is bumpy to the touch but not so much that it shows when I put a 15" trowel crosswise. Probably not so much thinset lift behind this sheet.

So the process is to move the ridges into the adjoining V space.

I pushed the spatula. Do you push or pull?

So, off to get some gray thinset and try the next sheet.

I am very appreciative of the time and committment of the professionals on this forum. I am always looking for questions that I can help answer to in some way give back.

Thanks

Edwena

Edwena,

I hold the knife at a low angle, maybe 20-30 degrees, and pull it to me. So that means I'm pressing the Kerdi into the thinset and that helps flatten the ridges.

The ridged trowel applies a measured amount of thinset on the wall. When you use the knife or trowel to push the membrane into the thinset, that's all you want to do...embed the membrane in the thinset.

You don't want to be moving thinset around underneath the Kerdi.

Mongo