(Editing so as not to bump to the top with a reply: I've found all of the needed answers. Thanks anyway! 
)
As I have noted on another thread or two, we're getting ready to build a new house. We have narrowed our choices down to two options: 1) Above ground house made from free/close to free construction scraps (DH is in construction), or 2) Underground house.
We know how to build #1 and already have most of the supplies needed. However, these materials would not go to waste if we went with option #2. They would be used for sorely-needed outbuildings.
I need your help on option #2. DH works in construction but with above-ground buildings and has never done anything below ground. We'd really, really prefer to go with underground because of the safety (tornado-prone area), low exterior maintenance, and heating/cooling efficiency. We're trying to come up with a cost estimate for this option but need some basic building info. By the way, there are basically no building codes to worry about in these parts. Cool, huh?
1. Wall thickness. Assuming the walls would be concrete, except the south-facing one, how thick do these need to be? I've read most places online recommend 8".
2. Reinforcement. Exactly how much reinforcement (rebar, etc) is needed for the walls?
3. Footers. What dimensions do the footers need to be in order to support heavy, concrete walls?
4. Drainage. How much and of what? I've read everything from gravel to sand to drainage tile (personally, I have no clue what drainage tile is but I'm sure DH does). Where are the drainage materials needed? I've read just around the walls, and have read some sites that state it is needed under the pad and footers as well.
5. Insulation and waterproofing. So many recommended materials for this that I don't have a clue what works best underground. I believe the layering is as follows, though, right? Concrete walls, waterproofing, insulation, another waterproof layer to protect the insulation, drainage materials, and finally dirt.
6. Ventilation. Moisture/condensation can be a problem underground so adequate ventilation is necessary but I've yet to find something that tells me how much and spacing.
7. Roofing. We're torn between 1) completely underground with concrete roof and dirt on top, and 2) top of walls and roof slightly aboveground with an insulated metal roof. #1 would be more efficient for heating/cooling, as well as safer for weather events. #2 would be more economical to build, as well as providing more light (roof would be a one-slope thing like this / only less slope, rather than a peak like this /\, and would have small windows on the back part of the walls that extend above ground) and would fit nicely with going solar later--solar panels. The roof and front of the house will be south-facing. We don't live in a frigid climate so summer with its heat and humidity is more of a concern for us.
8. If we do go with an underground concrete roof, how does that work? I'd imagine whatever forms are used will need to be incredibly strong, as will the built-in reinforcement. And how thick?
If anyone can answer any of these questions or point me to a website that does cover any of these topics, I'd greatly appreciate it!!
I have read websites on underground housing for almost a year now, off and on, but most aren't very detailed. Oh, and DH probably does know some of these things but, whenever we take on a big project and are in the decision-making process, we both do separate research. We both get our own answers in our own ways and then compare them at a later date. Works out pretty well in most cases! Just in case you were wondering why I'm asking such silly questions.
Whew! That was a lot of questions!
Oh, a couple more details:
Our soil is rocky clay--holds on to moisture too well so there will be more vertical pressure on the walls than in, say, the sandy desert. The house site is on a slope so the underground or earthbermed idea would work well, I think. South-facing slope. Summer temps in the 100s and winter temps usually 20s-30s with the occasional butt-biting dip into the teens. Average rain and humidity--not desert and not PNW.
)As I have noted on another thread or two, we're getting ready to build a new house. We have narrowed our choices down to two options: 1) Above ground house made from free/close to free construction scraps (DH is in construction), or 2) Underground house.
We know how to build #1 and already have most of the supplies needed. However, these materials would not go to waste if we went with option #2. They would be used for sorely-needed outbuildings.
I need your help on option #2. DH works in construction but with above-ground buildings and has never done anything below ground. We'd really, really prefer to go with underground because of the safety (tornado-prone area), low exterior maintenance, and heating/cooling efficiency. We're trying to come up with a cost estimate for this option but need some basic building info. By the way, there are basically no building codes to worry about in these parts. Cool, huh?
1. Wall thickness. Assuming the walls would be concrete, except the south-facing one, how thick do these need to be? I've read most places online recommend 8".
2. Reinforcement. Exactly how much reinforcement (rebar, etc) is needed for the walls?
3. Footers. What dimensions do the footers need to be in order to support heavy, concrete walls?
4. Drainage. How much and of what? I've read everything from gravel to sand to drainage tile (personally, I have no clue what drainage tile is but I'm sure DH does). Where are the drainage materials needed? I've read just around the walls, and have read some sites that state it is needed under the pad and footers as well.
5. Insulation and waterproofing. So many recommended materials for this that I don't have a clue what works best underground. I believe the layering is as follows, though, right? Concrete walls, waterproofing, insulation, another waterproof layer to protect the insulation, drainage materials, and finally dirt.
6. Ventilation. Moisture/condensation can be a problem underground so adequate ventilation is necessary but I've yet to find something that tells me how much and spacing.
7. Roofing. We're torn between 1) completely underground with concrete roof and dirt on top, and 2) top of walls and roof slightly aboveground with an insulated metal roof. #1 would be more efficient for heating/cooling, as well as safer for weather events. #2 would be more economical to build, as well as providing more light (roof would be a one-slope thing like this / only less slope, rather than a peak like this /\, and would have small windows on the back part of the walls that extend above ground) and would fit nicely with going solar later--solar panels. The roof and front of the house will be south-facing. We don't live in a frigid climate so summer with its heat and humidity is more of a concern for us.
8. If we do go with an underground concrete roof, how does that work? I'd imagine whatever forms are used will need to be incredibly strong, as will the built-in reinforcement. And how thick?
If anyone can answer any of these questions or point me to a website that does cover any of these topics, I'd greatly appreciate it!!
I have read websites on underground housing for almost a year now, off and on, but most aren't very detailed. Oh, and DH probably does know some of these things but, whenever we take on a big project and are in the decision-making process, we both do separate research. We both get our own answers in our own ways and then compare them at a later date. Works out pretty well in most cases! Just in case you were wondering why I'm asking such silly questions.
Whew! That was a lot of questions!
Oh, a couple more details:
Our soil is rocky clay--holds on to moisture too well so there will be more vertical pressure on the walls than in, say, the sandy desert. The house site is on a slope so the underground or earthbermed idea would work well, I think. South-facing slope. Summer temps in the 100s and winter temps usually 20s-30s with the occasional butt-biting dip into the teens. Average rain and humidity--not desert and not PNW.
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DH and I compared our notes last night. He talked to different types of construction folks about all of this (including a dirt fella who is familiar with our place). Our notes matched pretty well and we finalized our plan. I can't wait to get started!! 