Excavating an existing basement.
My Wife and I recently purchased a small craftsman, colonial, fixer upper built about 1935. We would like to excavate the basement to allow more usable living space in the house. The foundation is concrete block with a cement slab. The slab looks as though it was poured and patched a number of times. It is flaking in spots and obviously much thicker in others. The ceiling height, at the highest point due to the piece meal floor, is only 6’ 5″ slab to bottom of the floor joists. Then there are steam pipes, which have been added below. Ideally we would like to go down 2’ and add a bathroom and recreation area. I think my questions are these.
1. How do you sufficiently brace the foundation to allow for the extra depth?
2. Who would I hire to do such a thing?
Thanks for any help you can give.
Replies
Condo , This is strictly something that should be left up to the pro's.
What they are gonna do is put two steel I beams thru the foundation under the house and lift it up from the outside.Once they get it up to a heigth that they can work under they will dig out your basement , pour the slab and build the new foundation. Then they will set the house back down , pullout the beams and fill the holes.
Usually an Excavation contractor does this kind of work.
Good luck, Dave
Actually, depending on the condition of the foundation and type of soil it would be much cheaper to underpin the foundation and dig down. But, either way this is not a DIY project so an engineer is your best bet....that's not a mistake, it's rustic
If the existing foundation is sound, how about lifting the house up the two feet, and re-building the cripple walls to keep it at that height? It could be a cost effective solution if the climb isn't too much and your building officials will permit it.
See FHB April 1993 for "Digging a Basement the Hard Way" -- using a bobcat under a house.
-- J.S.
I think he's asking about lowering the floor (ie. busting up the concrete, digging deeper, and shoring the footings). It's do able but it's gonna be alot of work if it's a big basement.
Good luck!
John
definitely a lot of work. 2' down digs a lot of dirt.
I kind of like Sprung's idea. what would you have to do for that, let's see:
remove siding/sheathing, ck. utilities, etc.
jack the house, brace first floor
build cripple wall
resheath/side
remove braces
frame, rough-in utilities, remove steam pipes, whatever
if you excavated instead:
brace first-floor to remove posts if necessary, etc.
remove slab
dig
dig
dig
dig
dig
dig
find somewhere to put the dirt
pour new footings/foundation; maybe in stages
pour new slab
frame, rough-in utilities, remove steam pipes, whatever
the only other thing I want to say is...if you think you're deep enough, you probably ain't!
GO
1. There are a number of ways to "brace the foundation" and you should use the way suggested by...
2. A general contractor with experience in this type of work. This is not for everybody. A general contractor who does a lot of masonry and/or concrete work will be a likely cantidate. He will know if you need an engineer.
I've heard of a way that excavation companies can deepen a basement or crawl space using mining type equipment and a conveyor belt. They gain access thru the bilco or basement door. I saw this on a t.v. show about 10 years ago.....'this old house'?...can't remember. I think they cut dirt out a couple feet inside the original foundation and repoured a new one. Does anyone else remember seeing this?...or familiar with this technique?
FH ran an article showing a wine cellar being added to house by digging under the front door with a Bobcat.
It sure looked like a mining operation.
Not quite the same situation but thought I would mention it.
I recall that show, I believe that it was in Chicago. A row house if memory serves me right.
call in the house removers, Move the house back/forward/to one side, do your basement work, move the house back on top of new basement.