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Question DetailsAsked on 8/11/2015

Is it feasible to build a basement in East Texas or Florida?

I know about water tables and limestone and the other reasons why basements generally aren't build in the South. That doesn't stop me from wanting one. Certainly there is some combination of plastic or steel inserts, sub-floored basement french drains, and a myriad of other steps to waterproof a basement. Plastic under the foundation, and over the foundation? A wrapped foundation?

Can it be done? Are there companies will do it, and do it well? How much should I expect a waterproof basement in a wet environment to cost in addition to building a house on my own land? Would it be more economical to build a hill, then drop a basement into it with a house on top? Opinions welcome. I'm looking at buying some land outside of Jacksonville, FL...or outside of Houston TX, and would very much like a basement.

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1 Answer


Technically feasible certainly - look at all the highrise buildings with several story deep basements, or in-ground parking garages. Obviously more difficult to get watertight in chronically high water table areas, and requires special measures if in expansive soil, but not that hard to do.

Your best solutions - almost certainly most economic to build on a well-drained hill (diverting uphill runoff around the high side of the house well away from the foundation with swales or berms built into the landscaping or in extreme cases with brench drains), possibly build on a mound if in a chronically wet area (so the "basement" is physically "below ground" but the slab is actually a bit above the surrounding ground - basically an artificial hill, commonly built using materials from on-site grading, or a fully membrane underlined basement slab with drainage system and sump pump built-in and cast concrete foundation walls integral with the slab - so there are zero open joints or weak planes like there are in concrete block walls, with the foundation concrete being fully coated with bitumastic and then the under-membrane pulled up around the foundation and sealed to it sort of like a giant diaper. Note - if doing that you HAVE to have a sump pump system (which hopefully will never operate but is needed in case the membrane develops a leak - or full deep french drain system all around the house to intercept any water below foundation base level and drain it away.

One of the simplest solutions - a daylight basement (one side at ground level on the low side of the property) with simple bitumastic coating on the foundation (which can be block or cast concrete) and a french drain system installed all around the three "basement" sides below the footer level and draining out to ground surface level onthe downhill side of the house. Requires some moderate slope to the site - more for a "full" basement than for a daylight basement, of course.

Cost - additional to traditional slab-on-grade or crawlspace foundation - probably in the about $10-30/SF in your area - with daylight conversion from crawlspace almost certainly cheapest and full-underground in chronically wet area the most expensive. Around $20/SF is a pretty common number to add a basement to a new house design.

Would definitely, if talking a full "swimming pool" basement - basically one dropped into the ground in high groudnwater or periodic flooding conditions so basement has to be totally watertight, like a reverse swimming pool, require a contractor with proven experience in that type of construction, plus detailing of the impervious liner and drainage system by a civil engineer experienced in that. For a daylight basement with bitumastic and french drains any general contractor with experience in that (as opposed to just slab on grade "Houston" tuype homes) should be able to handle it fine.

Answered 4 years ago by LCD

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