DPM question for wet underfloor?

[jdwoodbury]

Hey folks,

Looking to finish off a side extension that we had built 12 months ago, but have mothballed while we focussed on other projects. The room is 7 x 4m and is a concrete slab, the builders put a DPM layer underneath the concrete our which is tanked up the side walls.

i have 125mm PIR boards to lay down, my question is do I need another layer of DPM on the concrete floor before I lay the PIR down?

So should it look like this?



or this?

[PhilboSE]

It's best practice to lay a DPM between the slab and the PIR as the slab can corrode the aluminium facing of the PIR.

[jdwoodbury]

PhilboSE said:

It's best practice to lay a DPM between the slab and the PIR as the slab can corrode the aluminium facing of the PIR.

Thanks, can that be a lighter weight DPM, like 500g?

[PhilboSE]

It’s just forming a barrier between the materials so a lighter grade would be OK.

[jdwoodbury]

Thanks