Hello all, My house is 100+ years old and has a stone and mortar basement foundation. It is about 7 feet from floor to joist because at some point in the past concrete footings and floor were added (the floor is lower than the footings by about 8", so I assume the footing does not extend all the way underneath the original stone foundation).
We are putting a 15x25 addition on the back. A contractor will be hired for the foundation work and I am looking to educate myself on where the old and new meet.
1) The current basement is about 7 feet, and the new will be 8 feet. What should the contractor do to ensure stability of the old wall when digging around it?
2) How will they tie into the old? From what I've read they'll scribe the form work to let the concrete 'key into' the old. Would there be any advantage pouring a concrete wall parallel with the old, in other words 'sistering' the old wall with new concrete?
3) How to continue the waterproofing/insulation from the new concrete onto the old stone foundation? While it is dug up I might as well waterproof it, as the bottom right of the old foundation faces up hill, so it sees the most water.
Any information is appreciated!