Expanding basement next to house?

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Old 09-05-06, 09:21 AM
dsw
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Expanding basement next to house?

My house sits on about one half of a double lot and we have an unfinished basement that is about 1/2 below ground. We're considering ways to use/improve the basement. In order to make it useable, we'll have to dig out the basement floor, dig down an extra foot or two and repour the floor. One additional, more extreme option we're considering is to also dig out the unoccupied half of our lot (currently all lawn) and expanding the basement to essentially double its current square footage. We would then recover the new basement with lawn.

Has anyone ever hear of this? Is it difficult? Costly?
 
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Old 09-05-06, 11:03 AM
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Expanding basement next to house?

In a normal basement, the walls sit on a footing. After the wall are poured, the slab is poured and sits on the footings.

One of the purposes of a slab is to preven the soil from moving the wall into the basement. Removing the slab removes necessary support. You do not know how the wall is attached to the footing (if it actually is) and cannot rely on any connection between the footing and wall.

Why dig out a basement then recover with a lawn? - That sounds very costly and extreme.

I suggest you have a contractor take a look at your basement and see if he can come up with a better plan.

Dick
 
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Old 09-05-06, 02:25 PM
dsw
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I'm not sure if my first message was very clear. We would remove one basement/foundation wall -- the wall that sat in the middle of our property -- and replace it with a steel beam to support the side of the house. The new basement would then extend across the entire lot. The basement would continue to be accessible from its current interior stairway, but the space would effectively be doubled.
 
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Old 09-05-06, 03:49 PM
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Expanding basement next to house?

A bit of a foogy explanation of your situation. -

Does the house occuy 1/2 of the property/lot or the whole property/lot?

Do you have a house with a basement under one half and none under the other half?

Does you house cover the entire "property"?

Normally, if you remove a slab that is poured against the basement wall, you compromise the stength and stability of the wall.

Dick
 
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Old 09-05-06, 06:07 PM
dsw
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Hope this clarifies:

The house occupies 1/2 of the property lot.

The basement is a full basement under the house. (So the basement also occupies 1/2 of the property lot.)

The basement floor does not seem to provide any structural function (it is about 1~2" thick, cracked, and slightly buckled in various places.)
Whether we expand the basement or not, we plan to remove the existing basement floor and dig deeper (floor to joist in our current basement is only about 6'3"; current floor is cracked, uneven, etc.)
 
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Old 09-05-06, 07:59 PM
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Expanding basement next to house?

Definitely not a DIY project based on what you have stated.

There are things that you do not feel are structural or important. If you are unwise and dig down without knowing what effect you are have with more soil pressure, you could have a big problem.

Call for help to get a good opinion based on your structure.

dick
 
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Old 09-06-06, 09:37 AM
dsw
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I'm not planning to do any of the structural work myself. I would do the interior work (framing for rooms, electrical, etc.)once the space had been set up.

My question relates to whether or not anyone has heard of a)replacing the foundation under the side of a house with a steel i-beam, and then building out underground (digging out our yard on the side to add basement space and then covering with lawn again) to expand the basement beyond the perimeter of the house.

Any thoughts?
 
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Old 09-06-06, 12:55 PM
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Based on your description, I think it would be more cost effective and a better return on investment to add an above ground addition, if you need the extra space. Even lowering the floor of your existing basement and finishing it would probably end up costing more than a standard above ground addtion.
 
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Old 09-07-06, 11:33 AM
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That still leaves the open issue as to where to park the Batmobile. I too think the most economical way to increase space would be to add onto the existing home at ground level. It sounds like your lot is large enough to easily handle a sizable addition.
 
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