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Discuss DPM on top of screed and under tiles in the DIY Tiling Forum area at TilersForums. USA and UK Tiling Forum

EdMac

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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 tile 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 https://www.tilersforums.com/forums/tile-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.
 
D

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 tile 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 https://www.tilersforums.com/forums/tile-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

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

Ajax123

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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.
 
F

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
 
D

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

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I thought thats what I said
 

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