DPM level with neighbours ground level

[Ay8452]

Hi guys,

 

I am having a single storey extension on my house and trying to find a suitable solution for the following problem.

 

On the side elevation with my adjoining neighbour (semi-d house) their ground level is approx 25cm above my DPM level. I am having beam/block floor in my extension. I have a 70-80mm gap with their ground level. If i out a french drain in here and "tank" the wall with something will that be enough to prevent problems? How deep should the French drain be, 15cm below my DPM level? Drawn a diagram as though I am looking back at the house from the garden, at the rear elevation.

 

Foundations are in and blockwork is about to start. Final spec is cavity wall with render finish.

 

Thanks 

 

Ali

[JohnMo]

22 minutes ago, Ay8452 said:

70-80mm gap with their ground level. If i out a french drain in here

How are you going to maintain the French drain? How are going to render?

 

Why do people build so close the boundaries. Just move to the correct house.

 

PIR insulation is the worst insulation for a cavity wall. Easy to make a bad job of it, difficult to get a good job.

[ETC]

Just tank the wall. Speak to Visqueen and they will do you a detail.