conecting new fundation with old stone fundation

[peter4x5]

hi
how may I conect a new cncrete fundation with the old one, which is stone (limestone).
300 years old stone wall building. Inside I want to build a few interior wall, which will support the roof .
Shoul I , and if ,how the new fundation must be connect with the old one?
thank you for help

[welsh brickie]

you can dig under the existing foundation to a depth of 300mm and flood the area with concrete creating a square block of concrete connecting new foundation to the old

[peter4x5]

what about rebar?
the new fundation has it so, should be any conection between old and new wall?
if the new wall start setting will be some damage to the stones?
sorry for english

[welsh brickie]

to connect rebar to existing you can drill holes in the foundation and feed the new rebar into the holes.And then concrete in place