Tile over Ditra supporting a very heavy tub - TilersForums.com

[misterclassic]

I'm tiling our bathroom, some basics - floor: 3/4" OSB T&G, 12" I-joists, 16" on center, new construction. I'm using the Schluter/Ditra-Heat uncoupling membrane but no heat cable under the tub that will be going in. The tub: Kohler slipper tub with four 1" dia. stainless legs and a composite skirt around the base, hiding the legs. The tub weighs 500 lbs. empty and holds 70 gallons of water. The floor tile is 18"x24". My question: with the tub full plus an occupant (two if I'm lucky), it will weigh in the area of 1350 pounds. Each leg will be supporting around 350 pounds. Will the tile over the DItra support this weight without cracking? Should I cut out a 3" circle through the Ditra where each leg will go and fill in with thinset, then tile over it to support the extra weight? Am I being paranoid? Thanks in advance!

 

[Ajax123]

What tiles are you using? As the bath is in four legs equispaced and in simultaneous contact it acts more like a UDL than a point load which would impose much differently and lower than a point load. That said the point load on each foot is about 150kg so 1500N or 1.5KN. This is actually pretty low. I know of a number of car showrooms with dita under tiles and they are fine. I'm not sure what the load supporting capacity of ditra is but I'm guessing its considerably higher than the load imposed by your bath.

 

[misterclassic]

What tiles are you using? As the bath is in four legs equispaced and in simultaneous contact it acts more like a UDL than a point load which would impose much differently and lower than a point load. That said the point load on each foot is about 150kg so 1500N or 1.5KN. This is actually pretty low. I know of a number of car showrooms with dita under tiles and they are fine. I'm not sure what the load supporting capacity of ditra is but I'm guessing its considerably higher than the load imposed by your bath.

Thanks for the quick response! As for the tile, I'll actually be picking it up tomorrow and I'll have more info then. My wife ordered the tile so it's a surprise! I feel a little better with your response, I just don't want to hear a crack as the tub is filling for the first time.

 

[benchwarmer]

What tiles are you using? As the bath is in four legs equispaced and in simultaneous contact it acts more like a UDL than a point load which would impose much differently and lower than a point load. That said the point load on each foot is about 150kg so 1500N or 1.5KN. This is actually pretty low. I know of a number of car showrooms with dita under tiles and they are fine. I'm not sure what the load supporting capacity of ditra is but I'm guessing its considerably higher than the load imposed by your bath.

Are the car showrooms on joists with osb boards merely ditra mat?

 

[benchwarmer]

Use hardie backer 👌

 

[Ajax123]

Are the car showrooms on joists with osb boards merely ditra mat?

No but that has nothing to do with it.

 

[benchwarmer]

No but that has nothing to do with it.

It has aye!
Because on the osb floor, the ditra will flex under the weight , on a concrete floor, it won't.

 

[misterclassic]

It has aye!
Because on the osb floor, the ditra will flex under the weight , on a concrete floor, it won't.

I can see that more blocking and support under the OSB is needed where the tub will set. I think that's key.

 

[steve1001]

Use hardie backer 👌

I'm no tiler, but hardie backer is not uncoupling. Also, it is not structural.

 

[benchwarmer]

I'm no tiler, but hardie backer is not uncoupling. Also, it is not structural.

Hardie will carry, and spread a hell of a lot more weight per m² than any other market competitor, and over a timber based floor is the best way to offer any kind of guarantee!
If you want simple decoupling over a new screed then obviously a mat will be the answer!
I've laid thousands of floors, always following advice and "trends"on which backer is best, and on any timber substrate the hardie is the only one to have never failed! So if you would like to come back to me, once you have done a little bit of research and a few hundred thousand metres of tiling, feel free 👍🏻

This place is an absolute wash with whoppers!

 

[steve1001]

Hardie will carry, and spread a hell of a lot more weight per m² than any other market competitor, and over a timber based floor is the best way to offer any kind of guarantee!
If you want simple decoupling over a new screed then obviously a mat will be the answer!
I've laid thousands of floors, always following advice and "trends"on which backer is best, and on any timber substrate the hardie is the only one to have never failed! So if you would like to come back to me, once you have done a little bit of research and a few hundred thousand metres of tiling, feel free 👍🏻

This place is an absolute wash with whoppers!

Sorry. I stand corrected.