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Lift House for Basement
From: msrn04@comcast.net
Category: Foundations and Basements
Remote Name: 71.194.167.63
Date: 03 Jul 2006
Time: 12:08 PM
Question: I have a 2-story house on a 4' tall poured concrete crawlspace (floor & walls). I am wondering about
lifting the house to extend the crawlspace walls up to an end result of a 8-9' high basement. Any comments, including
pricing, on this idea would be appreciated.
Builders Websource Answer®: Converting your crawlspace into a basement may sound tempting at first. However,
there are many factors to consider before you decide to proceed. Consider, for example that:
- Most municipalities have strict height limitations as part of the local building codes. Will extending the height
of the foundation walls by another 4-5 feet put the top of your house over the height limit? You already have a
2-story home, so check with your building official on any rules regarding maximum building height.
- Adding to the top of an existing stem wall isn't easy structurally. Normally, you want the vertical rebar from the
foundation to continue uninterrupted through to the top of the foundation wall, where it ties in to horizontal rebar
along the way. While it is possible to make such an extension, you're likely to have a weak point at the seam, which
will also be prone to moisture leakage. If you live in an area subject to earthquakes or high wind or snow loads, the
structural integrity of the foundation is of paramount importance.
- Your existing crawlspace probably wasn't designed with proper exterior drainage or waterproofing considerations.
As a result, your basement could be subject to a continual water problem if you don't engineer a proper solution up
front. Waterproofing basements are tricky enough even when built from scratch -- so you're depending heavily on the
quality of engineering and workmanship to ensure that any "add on" after the fact is designed to account for moisture
factors. Consider also that you may have to tear up landscaping and walkways to trench around your existing foundation
in order to install moisture barriers and drainage.
- Another factor is the actual cost. You could easily spend another $100,000 - $200,000 to extend your crawlspace
into a basement, depending on the area. Depending on where you live, will this extra cost put your home's value out of
balance with the rest of the neighborhood? If you plan to live in your house for a long time and really need the extra
space -- adding a basement might still be cheaper than moving to a larger home. However, in many parts of the country,
this added cost would be difficult to recover in the event you had to sell the home sooner than expected.
These are just a few of the many considerations you'll face in a project such as this, not to mention the cost of
moving out while the construction work is underway. If you can justify the financial impact to your bank account, we
urge you to consult with a highly reputable structural engineering firm to assist with the plans and provide project
oversight during construction. When it comes to structural safety and waterproofing, cutting corners will only lead to
an expensive disaster. Spend the money and do it right and you'll save in the long run.
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