Originally Posted by The Natural Philosopher

scudder wrote:

I have just built a single storey kitchen extension with a 150mm
reinforced concrete oversite base. The building regs required me to
install a DPM under the slab and another (more substantial) dpm layer
on top of the slab prior to laying 60mm of insulation and an 60mm
screed.

I am surprised at the lower DPM.


The central heating pipework will be laid in the screed. When testing
the pipework, I had a dry joint in one of the pipes and had a flood!!
The water got under the DPM and wet the slab and blinding layer.

I hope you are not laying copper directly in the screed...you shpould
only use plastic in the concrtet directly: Copper must be laid in
cojndut or possibly in some sort of faom insulation type layer to keep
cement and copper apart, and allow for differential expansin.


Anyway if it got under the DPM to the bit thats in contact with the
ground, forget about it., Ground is the wet side anyway.



Can anyone advise me if this needs to be completely dried out before i
put the screed down? I have exposed part of the slab by removing the
insulation and peeling back the upper dpm and this has slowly dried
over the week but the dpm is keeping the wet in where its still
covering.

I am completely puzzled as to what you have. Why two DPMS for example.

If youi ar about to spla down screed that is full of water, a bit more
seems to me to be irrelevant.


If i lay the screed next week, this moisture will be sealed in by a dpm
layer above and below the 6" slab, will it cause damage to the concrete
or reiforcement?


No. Water does not hurt coincrete, but again, I have NEVER seen a floor
laid like this. Noprmally the slab goes onto the earth, then its blinded
DPM'ed insulated and screeded in that order.

Copper pipes are NEVER laid in the screed, as your BCO will inform you.
For reasons you have discovered already.



Thanks.