Underpinning Adjacent Foundation

[kxa]

I am designing a three story masonry residential building that is 100’ long and the back of it will be right against a 45’ long house (only 5” gap). The bottom of the proposed basement foundation will be about 6’ below the house foundation (wall footing). Soil blow counts are 40+/ft. I am considering either helical or 3’ wide concrete piers for underpinning. Doing this for the first time. Any recommendations or suggestions, references or tips are greatly appreciated.

 

[MikeHalloran]

How will you seal/coat/paint your masonry?

How will the homeowner replace/paint/maintain his/her siding?

How do propose to get the inevitable toddler out of the gap?


Mike Halloran
Pembroke Pines, FL, USA

 

[XR250]

You should offer to dig them a basement as well :>

 

[oldestguy]

Never do underpinning the first time without some experienced help. I suggest contacting a reputable underpinning contractor for the job. You can then learn something and also it is likely that it will cost less. Will your insurance cover you on this? There are significant risks involved even if the blow counts are high. Release from the neighbor may cost plenty. Have your lawyer approve the agreements. Check the laws that may apply to this also. In some places the neighbor is responsible for holding up his building, dependent on depth of your excavation..

 

[PEinc]

Unless the wall to be supported is originally a party wall owned by both property owners, you probably will need permission to go across the property line and underpin the building. You not only need to vertically support the adjacent building, but you also need to retain the soil laterally under the building. That may be hard to do with helical piers.
Also, there are plenty of threads about underpinning in Eng-Tips. Do a search for a lot of good information.

http://www.PeirceEngineering.com

 

[dik]

Is there a reason that you have to be so close to the existing building?

Dik