building a patio

[nathalie]

Hi there, we want to build a patio with slabs along the back of the house, where there used to be a conservatory that we took down last year, the trouble is there is a solid concrete (uneven) fondation wich collect puddles of rain, if we lay the slabs on top of it then the patio will not be at 15cm bellow the damp course but at 7cm only. Plus we are worried about the water collecting between the slabs and the concrete foundation. Has anyone got any tips on a solution other than the enormous job of having to break the foundation?

 

[noseall]

you are correct, in that 150mm is the accepted minimum distance the external ground level needs to be below d.p.c.

in some scenarios building control have allowed this to be breached.
where there was a run of modern terrace houses on a steep sloping street, the drive ways of the higher neighbour was always breeching the lower neighbours d.p.c.

they remedied this by installing a low level lead flashing to combat the splash effect.

 

[nathalie]

Thanks for your reply, i see what you mean with the lead flashing. A friend of my husband suggested we leave a small gap between the slabs and the house and fill it with gravel!? Then paint a liquid form of dampproofing onto the wall. I don't know whether his tip is reliable or not. What do you think?

 

[noseall]

sometimes external sealents do more harm than good, trapping moisture in rather than letting the masonry "breathe".

 

[splinter]

Thanks for your reply, i see what you mean with the lead flashing. A friend of my husband suggested we leave a small gap between the slabs and the house and fill it with gravel!? Then paint a liquid form of dampproofing onto the wall. I don't know whether his tip is reliable or not. What do you think?

This is called a French drain google it for info