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  1. #1
    Join Date
    Mar 2010
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    1

    Default Digging out a basement

    Is it possible to extend a 4' frost-free wall down below the house an additional 3' to make a full basement? What would it take?

  2. #2
    Join Date
    Feb 2008
    Posts
    201

    Default Re: Digging out a basement

    Could you provide more info so your question can be answered.

    Will you be doing this yourself, or hiring an excavation contractor?

    For the most part, it should be left to a contractor.

    How many square feet of basement excavation are we talking about??

    Is the foundation poured concrete, mortared brick or cinder block, loose stone, etc.??

    How will you get the dirt out; are there cellar windows to get a conveyer belt in there, or can you knock a hole in part of the wall to get a small skid loader in there???

    Any photos???

    Even a small excavation involves an enormous amount of excavated dirt, rock, rubble that has to be loosened with power equipment; the walls have to be shored up before you begin.

    The town you live in usually requires a written civil engineer's plan and a city permit.

    Check out "underpinning",and "bench footing" on Page 3 at the site below.

    Unless the existing cellar wall is poured concrete in very good shape, the civil engineer usually requires adding an inside steel-reinforced sister wall (block or poured concrete) be installed in stages to cover the existing wall )---see "adding a sister wall"--Page 1).

    Please post back.

    http://illustratedhome******.com/gallery.php?gid=64
    Last edited by Dobbs; 03-15-2010 at 09:48 AM.

  3. #3
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Digging out a basement

    Quote Originally Posted by Chaps View Post
    Is it possible to extend a 4' frost-free wall down below the house an additional 3' to make a full basement? What would it take?
    Lots of money and patience.

    I agree with Dobbs and to add ----

    you will need to have an engineer design and approve the plan and possibly an engineer to evaluate the soil conditions. There are lots of concerns like how you preserve/shore up the footings at the base of the existing wall ---- so even at best you are likely to have a "shelf" around the perimeter of the basement at the 4 foot level . Then you need to submit the plans to the building department for approval.

    If you are also considering having finshed living space in this new basement there will likely be a need to go deeper to provide current minimum headroom requirement of 7 feet from finish floor to finish ceiling.

    More information than that, we can't really give you, too much depends on the details of the installation and your locale.

    Also, any plumbing will likely become an issue. It may not be possible to relocate the plumbing lower without completely re-doing the service connection.
    If that's the case you may end up having the sewer and main water line exposed at the 4 foot level within the basement.

    It's far from a " dig deeper, pour a new foundation wall and slab" proposition.

    Depending on the size of the home you are looking at $20+K

    Perhaps you might consider raising the home instead since the walls can be built using wood knee walls or block. This has it's own complications like if the there is a height restriction , you may not be able to live in the house while the work is being done , etc..
    "" an ounce of perception -- a pound of obscure "
    - Rush

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