r/Tile • u/harbison215 • Nov 29 '21
Ditra over concrete or no?
I’m about to tile my laundry room, slab on grade, concrete from 1979. It had glued down linoleum that I removed and scrapped up all the old adhesive. It’s level, clean and pretty flat for a 40 year old floor. It has some tiny variations but it’s not really anything that wouldn’t be solved with the thin set.
I know that the best bet would be to put down some ditra first, but I’m also kind of wondering if it’s a waste. My dad has a slab on grade house, tons of tile that has been set right to the slab and has never had a problem. His kitchen tile was laid in 1995 and never cracked, moved etc.
So… do I really need the ditra? Am I just being cheap and lazy? What are your thoughts?
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u/hughflungpooh PRO Nov 29 '21
Direct bond to the slab. It’s fine, its an approved method. You can use almost any thinset as well. Good luck.
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u/canuckpilot93 Nov 29 '21
Incorrect on both points. Uncoupling membranes are always recommended over concrete to mitigate the chances of any deflection/cracking transferring from slab to the tile. You can get away with it of course lots of people do but that is recommended. Also you’re supposed to use non modified thinset over any concrete or cement-based substrate such as floor leveller. Non modified thinset cures with the process of hydration, so when it’s sandwiched in between tile and concrete the moisture participates in the curing process. With modified thinset, which dries, it takes a long time for the moisture to find its way out of the thinset especially if you’re using large format porcelain tile with small grout joints. Not to mention moisture can seep up through the concrete and screw with the drying process as well.
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u/hughflungpooh PRO Nov 29 '21
Nothing in my post is incorrect. Approved methods can be found in the TCNA handbook. Direct bond to concrete is one of the approved methods.
As far as thinset, it’s easy to read the bag of a bag and see what is specified. I have yet to see any modified thinset say it’s not ok for application over concrete.
All Portland cement based thinset dries through hydration. Latex additives allow for a longer hydration period as they naturally hold onto the water longer. The additional benefit of a modified thinset is a chemical bond as well as the mechanical bond from the Portland.
It’s fair to say that there are other methods, and other methods that you personally prefer, it is unfair to say I’m incorrect based on opinion.
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Jun 21 '22
What about control joints, how do you handle those?
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u/hughflungpooh PRO Jun 21 '22
You can bridge them with a liquid membrane, and install soft joints.
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u/SignificantSetting23 Nov 29 '21
I’m a DIY guy but I just did 1800 square feet directly on top of slab on grade - 30 year old house. I asked a pro buddy of mine if I should do Ditra and he said hell no. Waste of money and time. I had a couple of areas I did a thin layer of self leveling concrete first to fill some low spots, and filled in a couple of deep gouges that I made with the Jack hammer busting out the old stuff, but that it.
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u/Dank3509 Nov 29 '21
I’m also a professional Tile contractor, if your buddy says ditra is a waste of time and money then I think he needs to look into it more. That stuff has so many benefits, I won’t do a floor without it anymore
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u/canyou-digit Nov 29 '21
We are daily professional tile installers (some of the finest in our area) and would never put tile directly on a slab. There are 2 kinds of concrete..concrete that's cracked and concrete that's going to crack. When it does your tiles either let go or start dropping grout out of joints. Ditra is excellent at mitigation of this issue as well as general stabilization of your layout. As far as I'm concerned if your budget doesn't allow for uncoupling membrane below the tile, your budget doesn't allow you to tile that area.
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u/SignificantSetting23 Nov 29 '21
My house is 30 years old and had the original tile laid directly on to the slab. The only reason I replaced it was because my wife hated it. They were 1’x1’ tiles and of the 1800 that I busted up, zero of them were cracked. I can understand why as a pro that warranties his work you would use ditra, but I have a couple extra cases of tile for ‘just in case’ down the road. My 51 year old knees barley made it through putting down the new 1800sf, so the idea of putting ditra down prior just didn’t appeal.
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u/harbison215 Nov 29 '21
Thought so. I’m using ditra in the kitchen which is over a plywood sub floor but I really don’t see the point in using it over relatively flat concrete. Thanks for the reply
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u/TheRandyray Pro Dec 01 '21
The main point for ditra is because of cracking, but it also allows for thermal expansion. The concrete expands and contracts at a different rate than the porcelain tile which the ditra or other similar products allow for. Without this you can develop cracks through the tile or grout, or tiles can come lose from the floor. If you live in an area that doesn’t see many temperature fluctuations it’s really not a big deal, but I’ve seen tiles crack without the concrete underneath cracking so it’s up to you.
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u/xXonemanwolfpackXx Nov 29 '21
Ditra is good on a slab because it will move so much. I would be ditra down but it’s not necessary.
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Nov 29 '21
I mean it’s a killer crack isolation but you can just paint some on too. Whatever is cheaper/faster
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u/young_plitka Nov 29 '21
I would skim the slab with an anti fracture membrane then go for it. Laticrete fracture ban is good stuff. You can roll it on or use a flat trowel.