New Edition Against A Fieldstone Foundation

[rory704]

Looking to see if anyone has any suggestions or experience.

My house was built in 1900 with a fieldstone foundation and I’m looking to add on an attached garage. The fieldstone foundation is about 7’ deep with a concrete floor basement. The new garage foundation will be 4’ deep with no basement.

Looking to see if anyone has built a poured foundation up against a fieldstone foundation. From doing research I found the attached details from Fine Homebuilding, but would like to get opinions from others.

Also, how concerned should I be about the added overburden pressure from the house’s addition onto the portion of the fieldstone foundation underneath it? Would I need to take any measure in my existing basement for added lateral forces onto the fieldstone after the poured concrete has cured?

Thanks,

 

[GeoPaveTraffic]

The existing fieldstone foundation has very little ability to support lateral loads. Therefore, I would not install the new foundation at an elevation higher than the existing bottom of flagstone foundation. Once you get away from the existing foundation you could raise the bottom of the new foundation.

Additionally, where plastic concrete will bear against the fieldstone wall proper bracing inside the basement should be used. The detail from Fine Homebuilding appears to illustrate this fairly well.

Good Luck.

Mike Lambert