Patio Levels - A bit of advice would be great

[bramleytom]

Hi,

I have met with a contractor a few times about a new patio. Seems very knowledgeable and I'm hoping to work with them. However I want to check if I am looking into this too much:

They initially suggested the following approach:

Build the patio up to 75mm below the DPC, which would leave a total drop between the house and the garden of 30mm over the 3.9m length of the patio. I asked if it was ok to go to 75mm (rather than 150mm per regulations) and they + this forum suggested it was probably fine. But the 30mm drop over 3.9m gives a slope of 1:130 which as far as I can tell is not substantial.

I've asked if we can increase the slope and they've suggested to raise the patio to the house, now leaving 45mm between the patio and DPC. This would give us a drop of 57mm which is more like 1:97 which still feels a bit too gradual from research.

However I am not experienced in this at all - so hoping someone can give some guidance! My logic is that we should excavate a bit more, put the patio 150mm below the DPC (current ground level), get the drop to around 65mm (1:60) and then deal with the rise this creates to the garden level another way.

Any thoughts would be appreciated. Thanks

 

[Cheslea2010]

You must absolutely keep 150mm between finished level and DPC. Water will breach your DPC otherwise and cause damp issues inside, not to mention green walls on the outside. Also, if you try to sell your house it will show on a survey. If you need to gain more of a gradient for drainage you can excavate and put a small retaining wall between the patio and the garden to compensate for different levels. Alternatively, go for a smoother finished surface such as porcelain which needs much less of a fall than riven slabs do to drain.