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Question DetailsAsked on 12/10/2016

how much to build 1000sq ft house under ground in nebraska

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Since most of Nebraska is likely to require about 4 foot basement foundation depth anyway due to frost depth, you are talking about doubling the minimum foundation depth - assuming you are talking single story, so just really off-the-cuff I would say probably about $10,000 more than a normal 1000SF house - which in Omaha market for instance is about $110-130/SF for standard above-ground construction. This assumes you will NOT be putting significant weight on the roof - if you are talking totally earth-sheltered housing or ESH (meaning 6-10 feet or soil over the top to eliminate the seasonal variation in ground temp) then a couple of green building guides say about $25-30/SF more than normal construction cost for that with "normal" divider load-bearing concrete walls in the house - or about $50-60/SF more for fully earth sheltered with open floorplan. Generally, what published information there is indicates about 10-20% higher cost/SF than above-ground houses if building an earth-bermed house (little top cover) or about 30-50% if fully earth sheltering - so the entire house (except a "sun exposure wall" is at least 6-8 feet or more below ground. The added cost is for the highly reinforced concrete "roof", and also due to special egress and HVAC issues with fully earth-sheltered houses.

Obviously, you would need to get a conceptual cost estimate from an architect familiar with ESH for your specific locale and design to find the cost for your area, but the above should do as an initial conceptual thinking stage number.

This assumes of course you will be above permanent and seasonal groundwater level (and an earth-sheltered house should always be 4-6 feet above water table at its deepest slab, if possible, to minimize moisture issues and avoid worries about leakage of the waterproof "cocoon"), and that you are building in alluvial/glacial deposits or soft bedrock, not bedrock that needs blasting (though that is generally the best building condition for earth-sheltered housing).

And don't forget to check with local building officials EARLY on about special egress and fire protection and HVAC requirements, and about waivers on window requirements - because for instance normal bedrooms have to have an egress window or exterior door as well as an interior door which ESH does not normally allow for (except maybe on an exposed hillside end), so the number of egress doors goes up and the maximum distance from any point in the house to them goes down from normal building code, and in many cases you end up having to have two hallways or a hallways and an exterior utilidor leading to the outside - and before you ask, vertical escape ladders are generally NOT allowed because they are not considered accessible by elderly or small children.

You might also talk with your favorite realtor about factors which could make it more saleable in the future, and what sort of resale market you would be looking at - because a fair number of people in California and Oregon and Arizona (the ESH capitals of the US) have found the resale market is VERY lean for ESH houses - there are a few artsy types and eco-fanatics out there looking for them, but the general buying public will not even consider one,so it is not unusual even in eco-friendly states for them to sit on the market for a year or more before receiving even a ballpark range offer.

Also pay close attention to a positive exterior water vapor barrier encapsulating all buried portions of the house, and the need for deliberate whole-house full-time ventilation to avoid moisture and odor buildup issues which normal exfiltration usually takes care of in above-ground houses, but tend to be a real issue in underground houses. Basically, you have to design the HVAC and water barriers for below-ground moisture/ groundwater issues, heavy rainfill infiltration elimination, and for "tight house" ventilation considerations. The groundwater/heavy rainfall infiltration issue commonly makes perimeter french drains, underdrains, and dual sump pumps a mandatory feature unless you have gravity drainage due to hillside construction - so experience has shown that hillside locations that can self-drain to a free surface are much easier to do to control moisture coming through the concrete by building a drain bed and french drains into and undeer the foundation system - and hillside construction also provides the generally (unless you are building a bomb shelter) very desireable south-facing glass curtain wall many ESH houses have. Which of course sort of totally contradicts the principle of ESH construction, but for some reason people seem to want to see the sunlight at times and not be like mushrooms or eskimos and live without sunlight for very long periods of time.

Of course, if you google phrases like - earth sheltered housing - you can find lots of articles and even a few magazines on the subject - just bear in mind a lot of what you read will be theroetical or written with a pretty strong bias - there is not a lot of factual information about the energy or moisture control issues with ESH. Most of the factual data are from the Department of Energy about their ESH experiment in Arizona, form a couple of unitverities about experimental ESH houses in Colorado, Utah, California, Missouri and yes Iowa, and military-source articles and a couple of Corps of Engineers and CRREL articles and manual on design criteria for totally underground strategic command and control and missile launch facilities, and for underground and earth-sheltered ammunition bunkers. Those latter documents provide much of the definitive design criteria and data on underground construction for habitation.

Answered 3 years ago by LCD

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