existing foundation wall abutting a new found. wall 1

[hutchattaylor]

we are putting an addition on an existing building with no basement. the addition will have a basement. how do we reinforce below the existing footer (aprox 3 ft below grade) and not diturb earth below; so we can dig for the new footer (approx. 12 ft below grade). the new block wall will need to be flush against existing block wall above grade. i need a detail.
thanks in advance!
D. Hutchison

 

[SperlingPE]

Underpinning is in your future

 

[SperlingPE]

Other option
Pull basement away from existing footing to get out of the influence zone. Construct a 4' to 6' wide section of slab on grade then start the basement.

 

[jike]

Underpinning methods may vary depending upon the soil conditions that you are dealing with. As SperlingPE said, moving the basement away will potential save significant money.