DIY Doctor UK DIY Forums

hi all,

this is my first time here so please be gentle!!

long story short-i have been ripped off by a builder and i'm now left trying to pick up the pieces on a now tiny budget.

my first query (of many no doubt) is, i've got/will have a 3x3 metre utility room. foundations done and walls up. in the inside is currently a long standing concrete walkway (1/4 of width) and long standing (with no movement at all or cracks) 3 inch thick paving sitting directly on top of gravely clay.

would it be possible to use this as a base for the concrete slab floor?
if i've got it right, put on top a layer of sand, then the DPM, then insulation, then the concrete (unsure of depth) followed by a screed.
would that be ok or does it all need digging up and using hardcore etc?
also, i've been searching through info and have seen mentioned a few times about 2 lots of DPM, do i need 2?

you need well compacted hardcore usually 150mm but it depends on conditons,50mm celotex/kingspan.Insulation on the harcore will stop the visqueen being pierced,then 100mm min concrete then screed 50mm

hi thanks for the reply.

so you're saying no DPM under the insulation?
wouldn't the insulation then get damp?

yes the insulation would get damp,Unless a double dpm is installed.Its stated on some plans, I have heard,But I have never seen it or been asked by the building inspector to install it .