Preparation of Sub floor and Dpm for underfloor heating and tiling. - TilersForums.com

[Chris Durrant]

Hi All,

I am new to the forum so I apologise for my mistakes.

I have lifted a laminate flooring from a hallway floor to expose loose tiles adhered with a thin layer of what looks to be bitumen.

After reading many people's posts I have scraped as much as I can off. Beneath the screed is a plastic DPM which seems broken at the edges.

I was thinking of Laying a liquid DPM over the existing screed, then priming with SBR Laying underfloor heating insulation boards on rsf adhesive, laying mat, self levelling, priming and then tiling.

Is this the correct procedure or should I prime onto the remaining bitumen and skip the DPM steps?

Thanks in advance.

Chris.

 

[Flintstone]

Hi Chris,
How do you know the dpm is broken, when you say you can see it, any photos ? Just up the edge ? Shouldn't matter if it's at the surface where it's broken

 

[Chris Durrant]

Hi Chris,
How do you know the dpm is broken, when you say you can see it, any photos ? Just up the edge ? Shouldn't matter if it's at the surface where it's broken

Thank you for your reply.

I can't see any Dpm where the front doors is. About 1" of screed has come away and there is no visible DPM. This is the same in a few locations.

I have attached pictures which I hope you can see from. You can see edges of the DPM in all the pictures so there is one there I'm just concerned if it's not full intact then the bitumen and the tiles I removed may have been a secondary DPM?

 

[Bond]

While your at it, might want to check the position of the wall damp proof course. If it's not continuous with the floor dpm, you can get damp bridging effect from floor to walls.

 

[Chris Durrant]

The wall Has its own DP but it's not continuous with the the floor, there are gaps

 

[Bond]

The position of the dpc is more relevant then, e.g. If the wall dpc is at or near the surface of the slab it may be okay. It's when the floor dpm is not returned up the wall or missing,and the wall dpc is positioned towards the base of the slab, then you have the potential for damp bridging from a damp slab and or wall below.