Foundations with two different ground levels

[colport27]

Firstly I apologise if the answer to this has been posted before but I cant find anything quite the same..
Our exisitng garage is in the back garden and we would like to knock it down and build it upon the drive adjacent to the house (would give us the larger back garden we require and the drive at the side of the house is a bit of a waste of space).
The biggest dilemma so far is that there is a current 9" brick wall at the edge of the drive that retains our neighbours land (their ground level is approximately 500mm higher than our drive). To achieve a garage the same width as the one we have (pretty narrow already) we would need to build at the same line as the exisitng 9" wall.
Ideally we would want to remove the existing wall, dig new foundations and reinstall a wall that would form the side of our new garage but capable of retaining the neighbouring land.
The main concern is how to build a 9" wall without a cavity that would be waterproof on the inside with the ground being higher on the outside.
Any advice would be greatly appreciated

 

[Shytalkz]

Check the foundations to the existing boundary wall, if ok (as in depth and the ground it's sat in) and there's no signs of lateral or vertical movement to the wall, build off it in 4" blockwork with 9" piers and render/board the neighbour's side.

You'd need to satisfy Party Wall Act requirements, but other than that, shouldn't be a particular problem.

 

[IJWS15]

Waterproofing is not a problem, you put a membrane on the outside which links to the horizontal DPC and ends 150mm above ground level. You then protect the membrane with render.

I used a product a bit like self adhesive flashing but 1m wide from Grace when I did one. Was not cheap but it worked.

 

[colport27]

Many thanks for your replies so far, the only concern I have with both ideas is that the neighbouring land is concrete which stops approximately 3 inches from the dividing wall. Without removing (and reinstating) the neighbours concrete I cannot see how we could render the face of the wall below the neighbouring ground level, would be a void 3 inches wide by 500mm deep.

 

[Shytalkz]

No, don't render the wall on the neighbour's side below ground level, leave well alone.

Can you cope with losing 4" or so off the width? If so, run the slab dpm up the inside face of the boundary wall to 150 above the neighbour's ground level and lap with the wall dpc to the new-build wall. Lay slab and build block wall in front of vertical dpm to protect it, don't bother tying it into the existing wall and compromising the dpm. Run it up to the wall dpc level, finish with a nice bit of MDF and put all those paint tins and other garage tat on it .

There are also proprietary render applications that could go on the inside face of the existing wall, which would cut down on the loss of width.

 

[colport27]

Once again, thanks for the reply. I must admit the idea of retaining the existing wall sounds great, will have to start digging through the drive to check the foundations (what depth am I checking for?).
We really cant afford to lose 4 inches in width so some form of internal waterproof render (any suggestions on type/make etc) would be best.

 

[Shytalkz]

It's less what depth and more what the soil is that the footing is sat in that's of interest. Dig a hole and take some pix and post them here.

Example of a tanking system: http://www.kiltox.co.uk/products/134.htm