ditra mat or not?

[wdk]

Hi, wondered if you good folks could advise on whether ditra mat is advisable/essential for my upcoming tiling. I've self built and extension approx 50m2 which will be a kitchen/diner (with 2.5x1.5m roof lantern) a utility room and a wet room. Laid ufh over kingspan and screed Larfarge Gyvlon to approx 60mm (2 weeks ago), expansion gap on every wall. I was intending to cure the screed and commission the ufh in a month or so - test with hygrometer, clean and seal the floor and then tile (uncalibrated slate). I've read that a lot of people use ditra, are there any significant benefits to using it? I've just been reading a thread where it seems the matting has parted company from the screed so I'm wondering if it will cause more problems than it solves. I'm not hugely experienced in the tiling department - any advice gratefully received.
Will

 

[Urban Essence]

Hi Will

Ditra Matting is usually used on plywood floors to absorb any movement before it reaches the tile and cracks the grout lines, or the tile.

If you are tiling onto screed there should be no need to use ditra matting

Rob

 

[Gazzer]

Hi Will

Ditra Matting is usually used on plywood floors to absorb any movement before it reaches the tile and cracks the grout lines, or the tile.

If you are tiling onto screed there should be no need to use ditra matting

Rob

Interesting, what happens when the underfloor heating is turned on and using a natural stone too....rather you than me.

 

[wdk]

thanks Rob, I ask as my tile supplier implied it dispurses and moisture left in the screed (how it would do this over 50m I'm not sure) whereas a lot of guys here say they always use it over ufh - to help with any movement I presume

 

[grumpygrouter]

Hi Will

Ditra Matting is usually used on plywood floors to absorb any movement before it reaches the tile and cracks the grout lines, or the tile.

If you are tiling onto screed there should be no need to use ditra matting

Rob

Really? Ditra has many more uses than that and i assume you are talking lateral movement of the ply and not vertical? If I was laying limestome, marble or other soft materials I would tend to recommend Ditra, screed or not!

 

[Stewart]

I would always use a de-coupler when using natural atone and underfloor heating.

 

[doug boardley]

same as Stewart for me

 

[Ken Bruty]

I wouldn't fix a natural stone directly to a ufh screeded floor, I've had to sort out so many problems with installations fitted this way, either grout cracking, filler popping out and worse - tiles completely split in half. I would always fix onto ditra matting where ufh is involved.

 

[Pebbs]

Will,

Youve gone all this way and spent money out, if you want peace of mind, do yourself a favour and get that ditra down. For me its not even an option not to put it down, belt and braces.

Pebbs

 

[Diggy]

Agree with all the others , Ditra is a must with stone on UFH , especially if the UFH hasn't been commisioned prior to tiling ( which it ought to be really ) . However , UFH is rarely commissioned b4 I get there usually , so Ditra is a given to negate the majority of the risk.

Got to start a limestone floor on Monday - 150m² - seeing Ditra in my sleep :0) . 4 tile pattern , biggest is about 900 x 600 . Thinking of hiring a crane to lift the big ones into place , me old back not up to it these days. :0)

Cheers

Diggy

 

[doug boardley]

Agree with all the others , Ditra is a must with stone on UFH , especially if the UFH hasn't been commisioned prior to tiling ( which it ought to be really ) . However , UFH is rarely commissioned b4 I get there usually , so Ditra is a given to negate the majority of the risk.

Got to start a limestone floor on Monday - 150m² - seeing Ditra in my sleep :0) . 4 tile pattern , biggest is about 900 x 600 . Thinking of hiring a crane to lift the big ones into place , me old back not up to it these days. :0)

Cheers

Diggy

I wouldn't even dream of starting tiling unless ufh had been commisioned first, ditra or not.

 

[Diggy]

I can assure you I make it very clear as to the ramifications and that I take no responsibilty for the consequences of not commissioning prior to tiling. Trouble is when you explain to the client/builder of the procedure - 5°C per day etc then 2 weeks to settle down - they simply haven't factored in the timescale.

Cheers

Diggy

 

[jasonj]

I aggree, Ditra everytime for me. Make sure the screed has 28 days to settle after insallation, fire up the UFH from zero and raise by 5 degrees per day. When at maximum temprature leave on full for 5 days then reduce by 5 degrees per day down to zero then leave for 2 weeks before any fixing occurs. This process should take about 2 weeks to commission. This will take out any expansion in the screed and allow you to repair any cracks that may appear. It is a long process but the firm who does my screeds reccommend this as an over safety precaution and they havent let me down yet on commissioning the screeds.

Use flexible adhesive for the Ditra Matt and if you want to be extra safe use a 2 part flexible adhesive.

I have had customers who refuse the Dittra due to cost so i get my solicitor to write a disclaimer saying that i have advised that the specifications require Dittra Matt so if there are any damage to the tiles due to not using Dittra then it is the customers responsibility and they alone are liable for any consequences that may occur from the advice given.

Stone tiling is getting more indepth and specifications need to be spot on due to possible legal ramifications later if not fixed correctly. A friend of mine got taken for 10K three years ago as he didnt use Dittra and didnt advise the customer correctly what the possible ramifications would be not using Dittra. The court ruled that as he was a proffessional tiler he had a responsibility and a duty of care to the customer to fully inform them of the possible dangers of not using Dittra would be....and he had nothing in writting to back it up!

Hope this helps Will

Jase

 

[Dan]

Just bumping this thread. If it's not a current topic then don't worry about it for now. Other threads like this can be found in the main tiling forum. If you do want to reply to it, please do. Your information may add value to somebody reading the forum in the future.

 

[jonnyc]

4 years on and I would never fix any anhydrite without ditra.there is not a complete logic to this . It's just that I have a system that I think works with anhydrite screeds. I prime dry screed with tilemaster prime plus 3/1 . Then fix ditra with tilemaster anhyfix. Fix stone or porcelain on top of mat with setaflex . This way cement based adhesive is never in contact with anhydrite screed.
Interestingly schlutertech dept even last week said that you can fix ditra on to anhydrite screed when r/h reading 2% or less.well you can and the mat copes with2% or less but they fail to tell you that dependent on adhesive you use,you need screed dry to 1% or less r\h for anhyfix or similar or .5 % or less for cement based adhesive to Fix ditra