Ditra Matting On Part Of A Floor

[James Green]

Hi,

We have a 55 square metre kitchen that we want to tile with 80cm x 50cm limestone tiles. We have NO UFH.

80% of the room is a newly screeded floor (extension) which is perfectly level (to within the tolerance of an 8 foot level placed in various places). The screed is dry having been down for 3 months.

Our challenge is the existing screeded area (20% of the floor and in one “strip”) is not level and runs out to approximately 6mm higher at one end of the room and 2mm lower at the other end when compared to the new screed.

We want to avoid having to pour self levelling compound over the whole area so one solution we have is to lay ditra matting on the new screeded area on a 6mm adhesive bed to raise the level by approximately 6mm. We can then use self levelling compound on the old screeded area to bring it up to the level of the ditra – and end up with a level surface.

What are the opinions out there on this solution? Is self levelling the whole area the only way to go? I looked at the ditra and it seems to have very little vertical flex.

Thanks for taking the time to read this.

James

 

[One Day]

The correct way (and safest/best use of funds) would be to ditra the lot but build up the adhesive bed a little on the new part. I have to say, an 8mm deviation on that area is tiny. Most of us would be overjoyed to have a floor so good! You can safely build up to 10mm on ditra btw.

 

[One Day]

You should really install a fixed expansion joint at the junction of the two floors AND use ditra.

 

[James Green]

You should really install a fixed expansion joint at the junction of the two floors AND use ditra.

Thank you for the quick reply. The approach you suggest makes perfect sense. My only reservation is how easy it is to build up the level using adhesive. Could I apply a 6mm bed of adhesive on the new floor (where the floor is out by 6mm), let this adhesive go off, and then lay the ditra on this (filling in the grooves of the gone off bed). This way using different notched trowels I can get a broadly level base before applying the ditra.

Could I ask what your thoughts are to the method of part ditra on the new screed and self level old screed to meet the the ditra? Would you be concerned about the tiles that are part on the ditra and part on the self levelled? Perhaps the flexible adhesive (webers) would cater for this movement?

 

[James Green]

The correct way (and safest/best use of funds) would be to ditra the lot but build up the adhesive bed a little on the new part. I have to say, an 8mm deviation on that area is tiny. Most of us would be overjoyed to have a floor so good! You can safely build up to 10mm on ditra btw.

Just to confirm - would you build up the adhesive bed underneath or on top of the Ditra?

 

[Flintstone]

6mm is nothing! Just build up a little where needed.

 

[One Day]

Just to confirm - would you build up the adhesive bed underneath or on top of the Ditra?

If you can do it underneath, it would be preferable (technically speaking). As a pro though, for speed and simplicity I'd just bed up on top - no more than 10mm or the ditra fails to work as designed.

The reason for covering the whole floor is to reduce the risk of lateral movement causing fractures. That risk is massively increased when 2 substrates meet. Flexible adhesive and slc will not accommodate this.
For example- ditra will accommodate a massive amount of movement - we're talking >10mm. Adhesive etc when it says "flexible" will be <0.5mm before failure (depending on manufacturer + spec etc)

Watch the following for a good grasp of what's involved: Schlüter®-DITRA 25 | Video | Schlüter-Systems
(bottom video especially)

 

[SJPurdy]

Hi,


We want to avoid having to pour self levelling compound over the whole area so one solution we have is to lay ditra matting on the new screeded area on a 6mm adhesive bed to raise the level by approximately 6mm. We can then use self levelling compound on the old screeded area to bring it up to the level of the ditra – and end up with a level surface.

 

[SJPurdy]

We want to avoid having to pour self levelling compound over the whole area so one solution we have is to lay ditra matting on the new screeded area on a 6mm adhesive bed to raise the level by approximately 6mm. We can then use self levelling compound on the old screeded area to bring it up to the level of the ditra – and end up with a level surface.

Why not SLC all the low area? You seem to be looking at options to raise the floor by that amount anyway.

You should not bed up under Ditra (as I understand it! - that is certainly an instruction with the Dural matting which is similar fleeced backed decoupling membrane (they recommend max. 4mm notched trowel)). I therefore recommend you confirm this with Schluter web site instructions (or tech help line). If you want to use Ditra then SLC under it leaving sufficient depth for the DItra on a thin adhesive bed.

 

[James Green]

Hi,

My only reservation with SLC is we've not done it before so a bit unsure how difficult this is on an area so large. But this with ditra on top is my preferred option based on the comments so far.

Would you mix a 25kg bag of SLC at a time and pour /spread with a spiked roller? Also would you cover the whole area say 3mm and then top up with another 3mm or lay 6mm of it in sections? My danger is the SLC dries before we have time to mix and pour the 12 bags needed.

 

[One Day]

Hi James, I assumed you were DIYing. I'd suggest leave the slc alone.
You might end up making matters worse without a bit of practise first!

 

[James Green]

Hi James, I assumed you were DIYing. I'd suggest leave the slc alone.
You might end up making matters worse without a bit of practise first!

Hi Impish,

My thoughts exactly!

One final option in the mix...

The raised area is quite small - about 4 square meters. How feasible is it to reduce the height of this area by the 6mm needed? I tried an sds drill with tile lifting but with little success. Perhaps score a grid with an angle grinder and then sds?

 

[LM]

58310: Erbauer Double Grinding Cup 105 x 22.23mm
Screwfix
Hire a dust shroud and use both with a 115mm grinder, it'll take about 20-30 mins tops to bring down to level
On the other hand would it be worth considering hiring a pro for this job, it's not a straight forward task when you start tackling mixed substrates and different levels?

 

[One Day]

Hi Impish,

My thoughts exactly!

One final option in the mix...

The raised area is quite small - about 4 square meters. How feasible is it to reduce the height of this area by the 6mm needed? I tried an sds drill with tile lifting but with little success. Perhaps score a grid with an angle grinder and then sds?

It would be an utter pain in the rear without proper eqpt.
Honestly - just bed up a bit or feather the difference over a few tiles.
Serious suggestion here: if you are going to be totally OCD about the levels (and it sounds like they could be disguised easily anyway) then I'd strongly suggest getting a pro in.

 

[LM]

58310: Erbauer Double Grinding Cup 105 x 22.23mm
Screwfix
Hire a dust shroud and use both with a 115mm grinder, it'll take about 20-30 mins tops to bring down to level
On the other hand would it be worth considering hiring a pro for this job, it's not a straight forward task when you start tackling mixed substrates and different levels?

I say again!!

 

[James Green]

Impish, LEE MAC, SJPurdy,

Thank you for taking the time out of your busy schedule to provide advice on the above, I think there is not enough appreciation on these types of forums of the willingness of skilled tradespeople to share their knowledge.

Looking at the all options and I whilst it is very tempting to have a go with the 115mm grinder, I'm going to go for the professional tiler route. No doubt they will think I am being OCD about levels!

Thanks again,
James

 

[Old Mod]

I think there is not enough appreciation on these types of forums of the willingness of skilled tradespeople to share their knowledge.
. No doubt they will think I am being OCD about levels!
Thanks again,
James

Thanks for your kind words, it's encouraging for members to hear they're appreciated, espesically when u consider, EVERYONE including staff, give their time free of charge.
Thank you.

U can never be too ocd with levels in my opinion James.
Perfect substrate, invariably leads to perfect finished floor in the quickest time, and it makes installation a joy!
And we all know a 'happy tiler' is a myth! Hahahaha

 

[jonesy7]

What's wrong with tiling straight on to the screed floor why does everyone want to use ditra all the time it just over complicates things you never herd of 5 years ago never used it never will and if every floor I tiled in the last 30 years was only 6 mm out I would be well chuffed

 

[J Sid]

5 years! I've been using it about 13 years and I'm sure some of here have been using it longer.
Why I use It with stone on a new screeds and most old ones is mainly because the screeds aren't layed properly any more. They are never covered to stop them drying to fast any more, which leads to screeds being weak and full of cracks which will transfer though to the stone.
I have redone many stone floors laid with out an uncoupling membrane full of cracks over the years.

 

[One Day]

What's wrong with tiling straight on to the screed floor why does everyone want to use ditra all the time it just over complicates things you never herd of 5 years ago never used it never will and if every floor I tiled in the last 30 years was only 6 mm out I would be well chuffed

Good for you. If it works for you.
Me and plenty of other tilers though will use Ditra when it's needed.
Maybe we're just mugs who pay good money for orange plastic?
Or perhaps you could explain for the benefit of all on here how you cope with tiling shift?

How about this: Would you fix direct to this? Tiles Keep Cracking

 

[Italy]

Good for you. If it works for you.
Me and plenty of other tilers though will use Ditra when it's needed.
Maybe we're just mugs who pay good money for orange plastic?
Or perhaps you could explain for the benefit of all on here how you cope with tiling shift?

How about this: Would you fix direct to this? Tiles Keep Cracking

ORANGE PLASTIC !!!! ahahhaha i love orange plastic!!!!
Use very little sin 😉

 

[Bill]

How about this: Would you fix direct to this? Tiles Keep Cracking

To be fair - that is not the same as there is no UFH involved in the posted job.

 

[One Day]

To be fair - that is not the same as there is no UFH involved in the posted job.

i know there's not but he said he's never used an uncoupler. He must have faced ufh before now. Just wondered what his approach would be. To be really fair i rarely use ditra unless it's stone going on heated. Porcelain and ceramic i tend not to use ditra unless the floors pap.

 

[Bill]

i know there's not but he said he's never used an uncoupler. He must have faced ufh before now. Just wondered what his approach would be. To be really fair i rarely use ditra unless it's stone going on heated. Porcelain and ceramic i tend not to use ditra unless the floors pap.

I have fixed lots on UFH without a decoupler but I have also fixed plenty with too.

I am not sure about these new screeds - seem to have more problems with those than we ever did with good old sand and cement.

 

[One Day]

I have fixed lots on UFH without a decoupler but I have also fixed plenty with too.

I am not sure about these new screeds - seem to have more problems with those than we ever did with good old sand and cement.

too true. Too true...

 

[One Day]

Good for you. If it works for you.
Me and plenty of other tilers though will use Ditra when it's needed.
Maybe we're just mugs who pay good money for orange plastic?
Or perhaps you could explain for the benefit of all on here how you cope with tiling shift?

How about this: Would you fix direct to this? Tiles Keep Cracking

@jonesy7 - apologies for the tone of my post. I was having a bad day and now I've re-read what I wrote I feel like I dropped my standards! The forums should be for open discussion and everyone's opinions and experiences are valid and up for debate. Sorry if I sounded like a "douche". 😉

 

[jonesy7]

@jonesy7 - apologies for the tone of my post. I was having a bad day and now I've re-read what I wrote I feel like I dropped my standards! The forums should be for open discussion and everyone's opinions and experiences are valid and up for debate. Sorry if I sounded like a "douche". 😉

No apology need mate it's a good Fourm and its all about opinions .....I just think we over complicate things ...

 

[J Sid]

No apology need mate it's a good Fourm and its all about opinions .....I just think we over complicate things ...

Until it goes wrong.
If a product has been developed to elevate a problem, and as a professional tiler I believe its our duty to use them to give the finish project every possible change of lasting the test of time, be it uncoupling membranes, tanking products or better adhesive or grout technology we should use them. 🙂

 

[jonesy7]

Until it goes wrong.
If a product has been developed to elevate a problem, and as a professional tiler I believe its our duty to use them to give the finish project every possible change of lasting the test of time, be it uncoupling membranes, tanking products or better adhesive or grout technology we should use them. 🙂

Why put a piece of plastic between a sound floor and a tile when a good quality flexible addhesive will do

 

[Aston]

Why put a piece of plastic between a sound floor and a tile when a good quality flexible addhesive will do

Because that piece of plastic has been designed to 'uncouple' therefore preventing any lateral stress transfering from the substrate to the tile. (A flexible adhesive doesnt have the same stretch tolerance).

 

[jonesy7]

Because that piece of plastic has been designed to 'uncouple' therefore preventing any lateral stress transfering from the substrate to the tile. (A flexible adhesive doesnt have the same stretch tolerance).

Surely you shouldn't be tiling on floor that's going to be moving lol ... How did we manage before plastic when adhesive were know we're near as good as they are today