Dpc

ds1980

BC have said we can put dpc above concrete slab in new extension but everywhere i look it says below.

http://www.planningportal.gov.uk/uploads/br/BR_PDFs_ADC_2004.pdf

shows that it is perfectly acceptable but appears that there is relatively little info about it going above rather than below.

Is there any reason why?

Andy_89

DPC would traditionally be above the slab, in the brickwork.

DPM could be below the slab. I would suggest they may also mean a Vapour control layer between the flooring insulation and screed.

http://www.buildingregs4plans.co.uk/foundation_floor_wall_3d_detail.php

ds1980

Dpc is about 6 inches above slab. But dpm is going one top of slab. Will be a vb on top of insulation before screed. Seems like it's horses for courses but was curious to know why the below slab with blinding etc was the norm as seems more faffy to me and that means more costs.

Furts

A typical detail is a membrane under the concrete slab to stop rising damp, and to stop the fines from the concrete being lost.

A membrane is then put above the slab for this is the cold side of the insulation, because the slab is uninsulated. Hence condensation and damp can occur. This membrane stops the damp penetrating, and damaging, the insulation.

dampdaveski

Hi ds,
DPC = Damp proof course, this is for walls to prevent rising damp, for new build this goes a minimum 150 mm above external ground level and should be level with the internal floor finish (assuming concrete)

DPM = Damp proof membrane, this either goes under your concrete floor OR sits on top of the base concrete before a screed is laid on top (with insulation) or a floating floor is laid (insulation and chipboard laid on a DPM ON TOP of the base concrete)

Thats about as exciting as it gets

ds1980

thanks guys.

dpc will be just below finished floor level but the outside will be 6 inches above the patio

BC are happy so I'm happy but it interests me when things can be done differently especially if it can save you a bit of money.

BC don't require another membrane on top of insulation or taping but i'll probably tape the joints anyway

Thanks for all the help