DPM and SLC

[JayW]

Hi guys

I need to uplift broken / loose marley tiles and screed the room in preparation for sheet vinyl.

The subfloor under tiles has bitumin residue however there are parts where it's pulled this up and it's now just the old substrate.

There is no DPM as house is from 1930.

My question is I've seen it recommended to go -

SLC
DPM
Prime / SLC (unless I use Ardex NA, then just go straight on top of dpm)

What I don't understand is if the floor has moisture then why doesn't the first coat of SLC get blown / uplift as it's in direct contact with moisture? Does it not make more sense to dpm first?

Secondly if I use Ardex NA can I get away with a cheaper dpm on top then prime and ardex again? The dpm1c is rather expensive and I've got a 20m2 room to try and sort. Or do you think I could get away with just ardex and no dpm as I read it's quite moisture tolarent?

Thanks

 

[dazlight]

No you will need the Dpm 1c
Not that expensive. You need a 10kg. What price you been givin?

You could do same system with Fball products or with laybond which could work out cheaper.

 

[JayW]

£150+ for 10kg

Sill screed first then dpm? If the dpm acts as a barrier then how come the first poor of slc doesn't fail?

Thanks

 

[dazlight]

It won't fail as it's moisture tolerant so let's moisture pass through it.
Done that system loads of times with 100% success.
Most times now though I do a quicker way which is with Uzin system.
Grind floor smooth
2 coats of PE404 dpm
Prime & screed

 

[JayW]

Thoughts on the Sika Rapid DPM?