DPM on top of screed and under tiles - Tile Advice

[EdMac]

We converted our garage and building control are insisting I install a DPM over the screed (even though the DPM runs under the concrete raft foundation of the house).

I will be tiling over the screed so looking for the simplest option. I could get a tin of blackjack and paint that on but it's pretty messy. I tried to talk to building control about the waterprrof properties of Ditra Matting - but they faded away when i started asking questions.

So I'm wondering maybe their is an adhesive that acts as a DPM or maybe best to board the floor and treat the board.

The screed is a sand cement mix approx 6:1 and up to 5 inches thick. I've left for a few months to dry properly as I gather it's around 1 day per mm drying time. There are hairline cracks so I am thinking of Ditra Mat even if not accepted as equivalent to a DPM layer.

Ideas welcome.

 

[Qwerty]

Contact @Mapei UK Marketing technical support, tell them your requirements and they will suggest a solution. Its likely to be Mapenet & Mapelastic after I spoke with my local Mapei rep last week.

 

[Flintstone]

Epoxy Dpm, such as Tilemaster or ultra to name two. Then your ditra if you like and tile.

 

[Dumbo]

We converted our garage and building control are insisting I install a DPM over the screed (even though the DPM runs under the concrete raft foundation of the house).

I will be tiling over the screed so looking for the simplest option. I could get a tin of blackjack and paint that on but it's pretty messy. I tried to talk to building control about the waterprrof properties of Ditra Matting - but they faded away when i started asking questions.

So I'm wondering maybe their is an adhesive that acts as a DPM or maybe best to board the floor and treat the board.

The screed is a sand cement mix approx 6:1 and up to 5 inches thick. I've left for a few months to dry properly as I gather it's around 1 day per mm drying time. There are hairline cracks so I am thinking of Ditra Mat even if not accepted as equivalent to a DPM layer.

Ideas welcome.

Black jack cannot withstand the hydroscopic pressure . It will let go of the background . When you did this work did building control not have to sign it of at various stages and therefore check your Dpm .

 

[Boggs]

Not sure why they would ask for this with raft foundations as the dpm should be directly under the screed anyway.

 

[Tilergal]

Ask them what they would consider to be an effective DPM in this scenario, turn it back on them.

 

[Ajax123]

If there is an operational DPM beneath the concrete you don't need one on top. However to get BC off your back you can use a epoxy DPM and sand scatter it before it sets. Vac up any loose sand once it's set and then tile.

 

[Flintstone]

If there is an operational DPM beneath the concrete you don't need one on top. However to get BC off your back you can use a epoxy DPM and sand scatter it before it sets. Vac up any loose sand once it's set and then tile.

You can also use prime plus grip over epoxy Dpm

 

[hmtiling]

You can also use prime plus grip over epoxy Dpm

Or Ardex na straight over

 

[Ajax123]

Ardex na is not a DPM

 

[Dumbo]

I think harry meant over epoxy

 

[Dumbo]

I have seen levelling compound let go of epoxy dpm that hasn't been sanded properly . When you sand it you should blind it with sand . What the term blind means is that you can not see the epoxy as it has been totally obscured by the sand covering . Then once the epoxy has set you then Hoover up any excess sand .

 

[Ajax123]

I thought thats what I said

 

[Dumbo]

I thought thats what I said

You did but I felt scatter is different from blind and could of been interpreted as a few handfuls of sand .