Connecting a new concrete foundation to an old stone one? 1

[jeansa]

How would you go about connecting a new concrete foundation with an existing stone one. What is the best way to do this? I am worried that the connection will become a hinge/weak point where water will infiltrate. A local contractor has suggested bolting steel pins into the old foundation before pouring the new one to tie the two together. Does anybody know if this works or is wise?
Soukwan

 

[sc]

Pinning the concrete to stone is no different than pinning concrete to concrete, except you do not know the properties of the stone, whether or not it has faults, etc. Hence with a bit of bad luck you may split the stone.

I would suggest an underpin/short beam under at the junction of the stone and concrete. The aim being to provide some support against differential settlement without placing too much direct loading onto the stone. The underpin will also minimise the risk of differential settlement.

regards
sc