Which trowel to use for Schluter Ditra?

[PJPro]

Hi.

I'm laying large format porcelain tiles over screen with wet underfloor heating. I'm using Ditra as an uncoupling membrane, with Schulter movement joints at door thresholds. As the title of this thread suggests, I'm not sure which size trowel I should be using under the Ditra.

The Schulter UK website suggests a 4 x 4 mm square notched trowel. A US Forum recommends either a worn 1/4 x 1/4 inch (6 x 6 mm?) or 11/64 inch (4.5 x 4.5 mm?) square notch. I can't find much discussion on UK forums. Here's the link to the US site.

Trowel size for Schluter Ditra - Ceramic Tile Advice Forums - John Bridge Ceramic Tile - http://www.johnbridge.com/vbulletin/showthread.php?t=97032

Some say that using too big a notch reduces the effectiveness of the membrane and makes it harder to avoid lumps and bumps in the matting. Others say the 4 x 4 mm size is understated and provides too little adhesive.

I've tried to source a Schulter Ditra trowel but they don't seem readily available in the UK. I was thinking of buying a 4.5 mm or 6.0 mm square notch Rubi trowel. Which one should I get?

Incidentally, I was going to use Mapeker Rapid Set Flex to bond the Ditra to the screed. I assume this is OK? I have primed the screen and then topped this off with some Mapei self levelling compound....so the Ditra will need to bond to the self levelling compound.

Any advice will be gratefully received.

 

[faceman]

4mm is fine. You can get 10m a bag then instead of 8. I always keep my adhesive nice and wet also so it is more tacky. I've had to try and remove it before and it was a nightmare so I know it works.

 

[Italy]

It depends on the slab, rough sand cement screed, preferably 6mm.
nice and smooth screed, could also work 4 mm

 

[A williams]

We use a 3mm trowel on ditra matting pretty much all the time ! We use the same trowel over and over because the tub stuff is super sticky!!

Hope this help's

 

[Dan]

@Schlüter-Systems Ltd

 

[Dumbo]

Personally 4mm

 

[One Day]

I have a few Ditra trowels. which are 3mm. On a lovely smooth flat floor or with ardex af200 it's fine.
On rougher floors I have used a 4mm mosaic or 6mm wall trowel but on a flat angle to keep the ribs low.
Runny wet adhesive works best.

 

[Dumbo]

Agree always adhesive on wet side

 

[PJPro]

OK Guys. Thanks for the advice. I think I'll go with the 4.5 square notched.

I'm also going to be doing some wall tiling. 30 x 10 cm ceramics. The walls have been freshly plaster boarded (dot & dab). I've primed the walls and was planning to use a 10mm square notched trowel. Is that too big? I used this size trowel for some large format wall tiles and it worked well but was wondering whether I could go smaller? 8mm? 6mm? The walls are good but not absolutely perfect.

 

[Schlüter-Systems Ltd]

Full details can be found here: Schlüter®-DITRA 25 | Function | Schlüter-Systems - http://www.schluter.co.uk/ditra-25.aspx

Quick answer is a 3x3 or 4x4mm notched trowel.

 

[PJPro]

Thanks for the advice but I've gone with 4.5x4.5mm notched trowel. Hopefully, this will be OK.

Any thoughts on the trowel for the wall tiles guys?

 

[PJPro]

I've put down the Ditra using Mapei Kerquick using the 4.5x4.5mm trowel. I mixed twice the amount of addy I needed. I reckon I used about 2.5kg per m2.