Addition with full basement on house with only crawlspace
Hi all, this is my first post. I read a book, “Foundation and Concrete Work” by the Editors of Find Homebuilding. Great book BTW. My particular question wasn’t discussed.
I have my existing home, Cape Cod style home, but the family has grown and we need more space. When I originally built this house I did not have a basement dug (I don’t remember why, probably money). Now I want to put a basement under the addition we are planning. The current house has a block foundation on a poured concrete footer.
My question is about when I excavate the earth next to the footer. Is there a possibility of failure due to removing part of the “stress bulb” of soil below the footer? I’m not talking about undercutting the current footer, but the bulb extends beyond the area the footer covers, is my understanding.
I’m planning on using ICF’s for the basement, at least 3 walls. The fourth wall, the one that will be next to the current house foundation has me baffled. Should I build wooden forms and pour a wall next to the existing blocks and footer and soil below the footer?
Thanks for any help you can give.
Patrick
Replies
I'd strongly suggest not excavating under or right up to the existing crawlspace footings.
I've seen people dig down a couple of feet away from the existing footing and pour a full height basement wall. You'd lose a bit of basement space, but it would probably work.
You could support the house and remove that section of crawlspace wall, and then replace it with a full height basement wall. But that would be tricky.
Would I dig all the way to the foundation at each end, to tie the new walls to the existing?
Otherwise, I like your suggestion and give myself a big DUH! for not thinking of it.
Thanks!
Patrick