DPM position

[hog]

quick question ...

building a floor sub-base ...

can I lay a DPM over the new concrete - rather than between it and the hardcore?

would I still need a barrier between the hardcore and concrete (i.e. because of sulphates)?

... reason is, the concrete floor will be built before the roof is done and I only want to tank it once it won't get rained on

thanking you ...

 

[ree]

The DPM goes below the concrete slab. Dont make work for yourself. Rain water is irrelevant to a concrete slab.

 

[hog]

thanks ree. it wasn't the rainwater affecting the concrete I was worried about. if I seal the area with DPM before the roof is up (I am a slow worker) won't the floor area just fill with rainwater that can't drain anywhere?

also that I didn't mention, there is a substantial amount of existing concrete that I want to re-use and match the level to. so I don't see any option but to lay the DPM over this section (and therefore also over the new concrete). but does it really matter if I don't DPM between the new hardcore and new concrete? the new concrete will be 100mm, does this need to be protected underneath in any way?

cheers

 

[hog]

mulling this over a bit , there should be very little space for much rainwater to wriggle down onto the dpm if it has a nice thick concrete slab on top and compacted hardcore underneath. so I'll start afresh and lay the hardcore + DPM + concrete now and before the roof is up. this gives me a nice flat work surface and if it ends up as a swimming pool I can always practise my front crawl

 

[noseall]

Stop fretting about the conc' getting wet or puddling, it happens all the time.