Basement excavation questions

8 years ago

Currently we have a half, unfinished basement. It is basically a storage and utility room. The remainder of the basement is a crawlspace (basically a big pile of dirt with a partial wall that holds the dirt in place). However, the half that is dug out, is only dug down about 6 feet. So we would need to dig down a bit more, maybe a foot and then excavate out. It would bring our liveable square footage up to 2400 square feet. (I say liveable because we are technically considered a 1.5 story home however we are looking to redo our dormers to make better use of the upstairs space).

I'm wondering if anybody has taken on this kind of project and if you could share costs, experience, value added, etc. Most everything I see talks about a full excavation and I think we're looking at more of a 66% excavation. And if you have done this, if you could tell me where to start on quotes, that would be helpful. A builder? A structural engineer? Both? With whom would such a project begin and be "managed?"

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PRO

The Kitchen Abode Ltd.

8 years ago

The process you are describing is referred to as underpinning. You need a very experienced GC to do this properly and it is very costly. This is usually only done when there are no other options to expand living space. It's typically less expensive to add a floor or an addition. Also, above grade living space is much more attractive than below grade, especially for resale. You need a Structural Engineer to evaluate the existing foundation to determine the feasibility of doing this. If you google this you will find examples of homes that have had to be demolished because the so called contractor did not know how to do this properly.

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Comments (6)

PRO
GN Builders L.L.C
8 years ago
You need an architect to get the design and a GC to do construction.

Digging out its not a problem, people do it all the time, they turn existing crawlspaces toa full height basements and connect with existing.

The price is different between regions and is based on the scope of work, design, etc.

Your best bet is to get a local contractor and see what they say.
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PRO
Patricia Colwell Consulting
8 years ago
These are pics of a basement that was done exactly like what you want to do. It was done before we bought the house but gave us a huge amount of space in a 1 1/2 storey home. It was not finished when we bought .We even added abathroom. This became one of our guests favorite spots the bedroom was quiet the media room had no windows and no one ever figured it out.
PRO
GN Builders L.L.C
8 years ago
last modified: 8 years ago
What TKA said, I missed this part "However, the half that is dug out is only dug down about 6 feet." I thought there is a full basement there already.

In your case, you need a company who can raise and support your house, and dig everything out and build a new foundation and set the house back down.

Something like this
PRO
The Kitchen Abode Ltd.
8 years ago
last modified: 8 years ago
Here in most cases where the basement is dug down the house can't be lifted, they are typically narrow row or semi detached homes. The basements are hand dug and must be done in sections about 4"-6". new footings are poured and the foundation wall is then constructed up to the old one. After proper curing they then excavate another section, this is done repeatedly until all the footings and foundation walls have been extended. There are of course many other complications to address, new weeping systems have to be installed and there are times when the existing sewer line from the street is now higher than the footings. When this occurs a holding tank and macerating pump must be installed to get pump the gray water up to the sewer line height.
User
8 years ago
Start at 100K, and go up, to WAY WAY up from there.

One woman on here had an additional 3’ dug down, and a new basement slab poured, and no other finishing at all. 80K I believe was her total. All she was looking for was enough head room for an exercise space, not a true finished living space.

Hand digging and not collapsing the home on yourself is the expensive part for sure.