Building out a basement
January 3, 2011 10:12 AM Subscribe
Dig a basement under an existing house? I have a crawlspace underneath an attached 100 year old house that I want to dig into a basement. What Do I need to do to make it happen?
posted by Napierzaza to home & garden (10 answers total) 2 users marked this as a favorite
Firstly, you are not my engineer. I'm in Montreal, Quebec Canada.
Basically there is nothing but a crawlspace underneath my house, it's be excavated underneath in the front because of water and electrical service upgrades before I bought the house. So there is about 4.5 feet deep hole in the front of the house.
The centre beam has settled and even rotted in some places because it was laid directly on the dirt 100 years ago. There's also some crumbling of the footing in the back of the house. We're currently digging a shallow tunnel (above the level of the footings) in order to access the areas that require repair as well as so we can replace some old water piping etc.
The soil is very hard packed and clay like. About 3 feet down it's slate with some sort of harder blue rock. The footings are directly laid on that rock.
I imagine I will either need a block wall filled with concrete, or a solid wall with rebar inside. Metal centre posts and a poured concrete floor.I think the best thing to do is bolster the joists with temporary columns, dig down 8 feet, replace bad beams and put in metal posts. After that we would dig towards one wall and build a wall somehow and finish with a concrete floor.
What I want to know is how I should go about this process. What kind of engineer needs to be involved and what kind of work is to be involved? Can I just find a structural engineer to make my plan up and then execute it myself? Do I need some sort of city permit? Does anyone have any recommendations for finding a reasonably priced engineer to prepare plans? PS I'm aware I'll be paying for a load of concrete or two.
FYI my neighbour has done a partial excavation and has a pseudo basement. He know's what's going on and supports the idea. He has not mentioned ever needing a permit for the work he had done.