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Although our house build is still several years away, we’ve started making decisions about it. I live in a tropical climate and have always felt a subterranean level makes great sense in terms of thermal insulation.

With zero experience building houses, I had not given it much thought. Structures here are built with concrete for the most part, and I was just told that I’d need to make sure I’d put in moisture protection for the subterranean part. And that this would not be cheap as nobody here builds such levels.

I’m just curious .... what’s involved in this!? How do you protect your structure from moisture when it’s all underground? And why is it different for subterranean levels than it is for above-ground levels that are exposed to the elements?

Some additional research said termites could come up through the concrete (!!!!?) and eat my (planned) wooden floor?

So now I’m wondering what other considerations there are in building underground. Any comments, links, etc are most welcome.

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  • A subterranean level is a hole in the ground that water wants to fill up. Concrete is good at keeping it out for a time, but small cracks develop and seams are usually not perfect. Most people lay down drainage pipe outside and/or inside bottom to drain water away, sometimes with used of a pump. Moisture barriers also placed underneath floor and on outside of walls. This also depends on amount of rain you receive. – crip659 Mar 11 at 12:43
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    This is a very valid question, unfortunately, I believe that it's far too broad for the SE Q&A format. I would suggest that you substitute the word "basement" for "subterranean level" and do some research on waterproofing basements. They are very common in the USA and that's the term we use here. The same concepts will apply to where you live, even if it's not a common addition to a house. – FreeMan Mar 11 at 14:02
  • Thanks both for your comments. – Rob de Jonge Mar 11 at 14:07
  • I agree with FreeMan. This isn't a good question for this site. Have a look at common basement/foundation waterproofing strategies from regions of the world where this is more common. The northern US is a good example. – isherwood Mar 11 at 16:01
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    The reason folks may not build basements in your area could be ground water level. The level may be fine today but if in an area that gets monsoons , hurricanes or just high winter ground water levels could all be reasons but it is worth looking into. – Ed Beal Mar 11 at 16:03
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My home is built on a slight slope and my shop (attached) is partially earth sheltered, it has about 4.5' stem walls. To ensure it was water proof, I had a contractor who specialized in this, spray the outside of the stem wall with a tar like compound and then they applied Delta Dimple Mat" over that (see link below). Then a well designed foundation drain to carry away and water that seeped thru the dimple mat. Fortunately for me, being on a slope I could simply let gravity do it's job to move the water. Depending upon your topology, you may need to drain it to a sump basin and use a sump pump to pump it to a good location away from the building.

Sorry for the product recommendation, I try not to do that, but in this case, I think it's justified.

https://www.dorken.com/en/our-products/products/residential/delta-ms.php

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  • Thanks very much for this. Gives me an idea of what I should be thinking about. – Rob de Jonge Mar 11 at 14:08
  • I used something similar 10’ on center each way under my basement slab plus a perimeter drain system around the perimeter about 12” below the slab, because of a high watertable. It works. – Lee Sam Mar 12 at 21:32
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Drainage and waterproofing, mostly. If your local contractors are not used to building down, getting the proper attention to details paid to those in construction might be difficult - workers tend to do what they are used to doing, how they are used to doing it; they can often be hard to get to change if you want something they are not used to doing.

Not sure about the termite problem, we don't have them (yet - who knows how long until we do as the climate warms) but even in a fairly dry basement I'd consider a wooden floor to be a risk due to potential moisture issues (vapor, no actual wetness required.) There are nice wood-look ceramic tiles available now that would be less risky. Even if the stucture is "perfectly" waterproofed, if warm, humid air comes into a cool underground level, condensation is likely.

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The above response (by Ecnerwal) is excellent in every front. Just want to remind you that, while you can plan everything, you can't plan something which you can't see. For underground construction, the type of underlaying soil, and seasonal ground water elevation/fluctuation add complexities, that can drive up the cost significantly. Thus, it is imperative to contact the engineering service/company that are familiar with local conditions and practices in the planning stage.

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  • "The above response" could be different for every user. There are 3 sort options, they're all user selectible, and they're based on dynamic conditions so even for you, yesterday's "above response" may not be the same as today's "above response". If you want to address one in particular, it would behoove you to specify the author of the post, or even link to it by copying the URL in the [share] link below the answer. – FreeMan Mar 12 at 18:53

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