We have a 100 year old house with a stone foundation. We want to add on to the house, but will need to add a full basement to the addition (38' X 20' addition) We do not intend to access the current basement through the addition basement.
Our question is simply, how to join the concrete and the stone on 38' side of the house without disturbing the structure of the current dwelling?
Install piles, 2 feet away from the foundation And at the end of the addition Install bolts through the new wall and the existing structure.
Cut back the sheathing on the existing wall, and overlap the new steathing from the addition the the existing studs on the house. Any stucco wire and paper if it's stucco. Or just butt it up to the existing house, And use a control joint from the addition to the existing house to allow for movement.
It all depends on the way your going to build it. You could just start the addition from the floor joists of the house.Some time it's better to allow for movement, Instead on overlapping everything, and getting upset later When the shifting starts. If you allow for shifting, then as long as the addition is attached, Shifting won't be a problem.
First you need a structural engineer or a very good contractor to check the condition of the existing foundation. They will need to determine how to proceed without disturbing the foundation.
When the new foundation is poured, either ICF or tradional forms, the forms will be scribed ( cut ) against the old foundation wall for a tight fit and the concrete poured with pins tied into the old foundation for a solid connection.
You pose a very good question.
First off, you should definitely have architectural drawings for this project and likely (but not absolutely) a P.Eng (Structural Engineer) that the designer would consult with during the design phase.
Having said that, my recommendation would be to temporarily support the existing house with a beam and lally columns or a temporary wood framed wall.
Then removed your existing stone foundation wall along the length of wall that you are adding too and replace it with a new poured footing and CMU (concrete block wall). Whether you have access from the existing basement to the new will have no bearing on the new wall (might as well, but not necessary).
As you are already building three new foundation walls for your addition (I assume) the addition of a fourth is not a big deal and any competent General Contractor should be able to take care of the temporary support.
There are a number of reasons to seriously consider this option.
1) A house the age of yours is most certainly built without a footing and you will now be adding to the load carried by that foundation wall (the amount of the load would be greatly affected by the direction of the new floor joists) and it only makes sense that three of your new walls will be built to todays standards, why not the fourth.
2) In a 100 year old house there is more than likely some sagging to the floor. This will provide an opportunity to address at least some of those and make matching floor elevations in the new addition easier.
I am going to run out of room here, but the most important consideration is the depth of your existing basement! As a rule of thumb, the load path of your home is transferred to the Earth at about a 45 degree angle. If any new structure is constructed close to your old wall and is NOT as deep and the load path passes through your existing wall, it WILL fail catastrophically. Likewise the opposite is true and your current wall could compromise the new. You are far better off replacing 100 year old building technology with new whenever possible.
As a bonus, if you size the footings correctly and install a beam, you could essentially open up the complete wall if you wanted to and have a much larger basement!
Best of luck with your project!
The Cedarbrook Group
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