# Forum Home Renovation Sub Flooring  installing dampcourse

## old stoney

building a stone house but having problems working out the dampcourse.
Walls are 550mm thick,fieldstone not sandstone so irregular shapes. Don't want bitumen sticking out( ie, a drip line) but am considering using bitumen foil or similar within the wall. guess there will be 20mm from the edge of the dampcourse to the edge of the wall. Will this still work ok?? Is it legal?
cheers

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## Hoppy

The damp proof course is best installed directly on top of the concrete slab or footing, but it should extend to the full width of the masonry. You can use an embossed black polyethylene film (viscourse) available from builders supplies that can be trimmed to the line of the wall on completion. I know they supply it upto 450 wide, not sure if you can buy it 550 wide, so you might like to buy 2 rolls @300 and overlap in the middle of the wall.
Hoppy

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## Oldsaltoz

I'm no builder but work on new homes every day and I suspect you will be advised the black plastic strip material, it can be trimmed after the stones are laid. 
If you cut the damp course short of the edges you will defeat the whole purpose of installing it in the first place. 
No doubt a brickie will be along  soon with some more informative advise. 
Good luck. :Smilie:

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## Bloss

> The damp proof course is best installed directly on top of the concrete slab or footing, but it should extend to the full width of the masonry. You can use an embossed black polyethylene film (viscourse) available from builders supplies that can be trimmed to the line of the wall on completion. I know they supply it upto 450 wide, not sure if you can buy it 550 wide, so you might like to buy 2 rolls @300 and overlap in the middle of the wall.
> Hoppy

   :What he said:  although overlapping a no-no. A quote from a manual I have: 
"Membrane type damp proof courses (DPC) must be laid across the full width of the wall and must project through the mortar on either side and be completely visible after laying and cleaning is complete. Recessing DPC below the edge of the masonry so that the mortar bridges the DPC invalidates its use and is therefore entirely unacceptable. Bridged DPC may lead to rising damp, salt attack and or accelerated corrosion of the built-in components that may lead to structural failure. Recessing flashing below the mortar although common is not good practice as it allows the water that should be shed to soak into the wall below the flashing." 
This is especially so with sandstone - not so much with less pervious stones. Note too that the DPC should not be bridged later such as with paint or render. Various flashing is available up to a 1m wide (not all - most  max at 450 or 600mm).

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## old stoney

thanks for all the help.
will post pics when under way!!
cheers

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