Increasing Basement Height - Stone Foundations

[SinStrucEng]

Good day and happy holidays folks,

I have a client who wishes to deepen their foundation (increase the total basement height). I have a standard detail for this that is typical to my part of the country (Ontario, Canada) when completing this work on poured foundations. I have used it many times before and it's relatively simple too:

Difference in this case is that the house has a stone foundation. The stone foundation is in relatively good shape. The house is a side-by-side duplex (my client owns one of the two sides), two storeys above grade, clad in brick. Other than getting a geotechnical engineer to provide additional commentary before we start, does anyone have any other feedback or comments? Thoughts on using the above style bench underpinning? I will be going back to the house in the New Year and will give some thought on how to pin the new foundation elements to the existing stone wall - that's my greatest query, at this point. Many thanks.

 

[PEinc]

Your detail will significantly reduce the floor area of the basement. Why not just underpin the existing stone foundation wall.

http://www.PeirceEngineering.com

 

[dik]

I've underpinned numerous stone foundation walls (without footings) by excavating under the wall in parts to a foot below the required basement level and cast concrete extensions to the stone wall. This is repeated to the part of the wall adjacent in about 3'-4' segments. I cannot find the detail, but the following are the notes. Dimension 'D' is the length of the excavated segment.:

I've also done 'benching' similar to what you have shown.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[jerseyshore]

I'm not a big bench fan unless it's the only choice. Regular 2 or 3 stage underpinning as PEinc and Dik describe are usually preferred.

 

[dik]

Neither am I, but rolled it out as an option.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik