Digging slab for extention next to existing rear elevation

[cox377]

Hello guys,

I'm marking out the foundations and slab today. I dug down a test pit next to the rear elevation of my property to which the single story extension will join onto. The foundations of the house are only 300mm deep.

I'm not concerned about the new foundations as they run at a right angle to the rear elevation, however the concrete slab will mean I dig to the same level as the existing foundations even if I go with a minimum 75mm hardcore/25mm sand/DPM/100mm insulation & 100mm slab assuming I can smooth off without screed.

The house is a standard victorian semi. The total rear elevation of the back part of the house is 7m. So half that will be exposed.

How do you guys normally go about it.

Thanks in advance

James

 

[Static]

Digging to the same level as existing foundations shouldnt be a problem.. only if you dig below should any unusual measures be in place..
(Remember to pipe all your air brick locations through the extension..)