New Poured Concrete Wall Connected to Old Stone Foundation Wall

[woodman1967]

I have a friend who wants to add a frost wall under an existing addition to an 120 year old home. The couple had purchased the home within the past year. The main home was built on a mortared stone foundation forming a crawl space under the home. At some point a small addition was added (400sqft). This addition was built on a footing on grade. The home owners want to put in a frost wall (the homeowner is a retired foundation guy and has poured many foundations over the last forty years) and, of course do it himself. His plan is to support the addition (without raising it) then pour a 24" concrete wall on a footing below the frost level then add concrete block to the sill of the addition. The new poured concrete/block wall will meet the old stone foundation wall at 90degs at two points. The old stone foundation wall is in good shape. Is there a way to make this connection using rebar and epoxy? Should he extend the rebar through the old wall and anchor on the other side?

 

[r13]

I don't quite get the situation, but I think the new wall should not be tied to the existing stone masonry, an expansion joint should be considered. Provide a sketch will improve the quality of responses.

 

[woodman1967]

OK, please find attached a quick drawing showing an elevation and plan view of the concrete wall/stone wall connection. Does this help clarify?

 

[r13]

My original suggestion stays, you should be able to design the new wall without utilizing the stone wall. If a rigid connection is made, you are risking in damage both.

 

[PEinc]

This sounds like a concrete pier underpinning project. Dig and shore several pits under the existing addition foundation about 4' wide at 12' c.c. Leave a space of about 2.5 to 3 inches between the top of the underpinning piers and the bottom of the addition's existing footing. Then, drypack the gap. Repeat as necessary until the entire addition foundation has been underpinned.

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