decoupling membrane

[matty]

Hi I am laying 14 sqm of 12-15mm sandstone tiles onto a concrete 1930's floor. DPM is unknown - but damp does not appear to be an issue- i don't really want to dig up concrete and lay a dpm. It was previosuly sealed with bitumen which was about 15mm thick. I wasn't sure of its purpose as a self leveller/ adhesive for the lino i took upor whether it was a dpm but it was coming up and now itsup so theres no going back.


my current plan is to lay 10mm insulation board with underfloor heating on top followed by tiles BUT i recently came across decoupling membrane which i hadn't previously known about. would this potentially help stop any movement if any moisture did come through? have flexible tile adhesive.

Also would i put this on top of the underfloor heating? i.e. go insulation, heating, decoupling and then tiles.

any help/ advice, opinion welcome

cheers
Matt

 

[Qwerty]

First of all I would definitely fit a decoupling membrane in this scenario.
Secondly, yes decoupling membrane above UFH. Thoroughly advise encapsulating UFH in self levelling compound though (make sure it is suitable for UFH).
Thirdly, what experience do you have with UFH systems and laying natural stone?
My advice regarding the floor is that you need to ensure there is a damp proof of some description. I would call Mapei technical to discuss things as they have many DPM solutions.
Either way, you need to make sure you know what you are doing and that the floor is sound and flat.
Any photos?

 

[DHTiling]

Hi matt.. this bitumen.. it would have been poured to combat the damp.. this can in turn drive it to the walls..

But back to your job in hand. if the bitumen/Asphalt is bonded well then IMO you need a slurry bond for adhesion purposes.

 

[Qwerty]

As far as I read his post dave it sounded like all the bitumen was up? But yes, I agree any residue can be tackled by mixing up a slurry coat

 

[matty]

Cheers for your replies guys. So would a product like Ball Stopgap F75 be suitable to go down first as a dpm? the bitumen came up very easily - it was a brittle slab and not stuck to the concrete as such so no residual bitumen in the concrete.

The underfloor heating is matted so can be tiled straight on to so dont think a self levelling compound is needed but will look at whats available.