Ditra mat for 10mm porcelain on new 65mm fibre screed?

[Deleted member 51092]

Hi all, apologies if this has been asked before, but couldn't find an example for this situation.

Question is do I need to decouple with Ditra mat (or similar) or will it be fine without?

• Tiles are 10mm thick porcelain.

• This is in a new extension linking to existing kitchen.

• The new extension ground floor construction is 65mm fibre reinforced screed, over insulation over 150mm concrete slab. No UHF, just normal radiators. New floor area is approx 28 sq m.

• The existing kitchen floor abuts the new floor (no joint) and is a concrete slab that just had a bit of levelling compound.

• Total floor area is approx 45 sq m. And approx 9.5m x 4.5m sized area.

Thanks in advance!

 

[Simon Dale]

Hi, nice cleaner lol. If it was my house I would use an anti fracture mat. Belt and braces

 

[Flintstone]

Chris,

Is the new screed pumped in? How long has it been down? Where the two screeds meet is going to be a potential area for movement in my opinion, and also new screeds are susceptible to cracking, as Simon say, assuming the new screed is fully dry then an anti fracture mat will be a good choice or ditra. If you want to tile on this before it’s fully cured, then ditra is the way to go.

 

[Deleted member 51092]

The screed has been down for two weeks now. I don't know how it was laid as I was away on hols. So far no signs of cracks, perhaps due to reinforcing fibres. The new floor is on a ground bearing slab on a solid chalk subgrade, so I'm not expecting (fingers xed) diff settlement to occur at the joint.

 

[Spare Tool]

If you cross that joint i would hedge bets it will crack your tiles, just like crossing any other expansion joint...
Try starting your tile setting out with a grout joint directly over the joint in the screed then just colour match silicone that grout joint and grout the rest.