Build an underground shop - why not?

[jinman]

I've been plotting and planning to build a nice 40 x 60 metal building for a long time. As I was excavating in my sandpit recently, I suddenly had an epiphany moment and realized I have the perfect place for a very large underground structure. I've included a picture of the site. I was thinking of making a pond in this location, but lately I've begun to think about drainage and how large a runoff I can provide for normal annual rainfall. I don't think I can direct enough runoff to keep two ponds full.

In the first picture below, the sandpit I've been using is in the foreground. The area with the deep gully and mounds at the top would be a single pond and my underground shop would face toward that pond so that the approach and front of the shop would have a nice full view of the pond.

In the second picture, the view is reversed from the bottom of the pit looking up. At the back and sides of the excavation, I have sloping ground that goes from 20' deep down to about 12' deep. My feeling is that I can build a shop back into this hillside with a 12' ceiling and columns inside for supporting the roof which will be covered with dirt.

I took measurements and I can easily fit an 80' x 60' structure underground in this area. I think I'd probably go 80' x 40' or maybe 80' x 50' with three rollup doors and one walk-in door on the front side. I might also build a concrete tunnel back to my house so we can use this as a storm shelter and also an underground cellar. My feeling is that I can use solar tubes for lighting and have a structure that's warm in winter and cool in the summer with very little heating/cooling costs. Ground water and seepage will be easily controlled since this soil is very dry.

So, does anyone have any experience with a structure like this? I know PatrickG built an underground section on his new house in Oklahoma, but I don't want anything as nice as a living area. This can be painted concrete walls and ceiling; very little finish work. I can even run electricity, plumbing, and compressed air in hanging channels. I'm not sure what kind of columns or the number required to put 4000 sq ft under an earth roof, but of course a shop is best with as much open space as possible. I believe a 12' ceiling will be plenty for any equipment I might want to put inside.

So if anyone can help me with experience or suggestions, I'm very open to all advice. I talked to my wife about this and she is very supportive. I don't think she wants a large shop blocking her view. She'd love to have this underground shop instead.

 

[EddieWalker]

Jim,

I'd love to see you do it just because of how unique and complicated it would be. But I'd have to caution you that it will be allot more money then building a metal shop on a flat concrete pad. While the concrete footings to support the walls and the concrete for the walls will be allot more money, the place that will really add to the price will be a roof capable of supporting the load of a dirt roof.

With a standard price of a metal building, I'd guess that you triple that price going underground.

Eddie

 

[mikim]

$$$$$$$$$$$$ but too cool! I'm betting you'd be looking at an arched concrete roof. You might do a search for earth builders in the area.

 

[jinman]

$$$$$$$$$$$$ but too cool! I'm betting you'd be looking at an arched concrete roof. You might do a search for earth builders in the area.

Did you have to use so many $ signs?

Yeah, maybe like a monolithic dome. The roof is what has me worried the most and what will drive the price way up. I would probably cut the costs immensely if I made three walls surrounded by dirt and the roof made of steel supports with normal sheetmetal. If I want to put in some type of hoist supported by the roof, it will be even more. It just seems to be such a waste to start filling in the excavation that Mother Nature provided me. Building an energy efficient earth sheltered shop also seems to have a long-term payback. The "cool" factor Eddie mentioned is also kinda appealing.

 

[Egon]

Do you want the roof covered in dirt too?

 

[CurlyDave]

Covering the roof with dirt will mean that you will probably have pillars or posts inside to hold the weight. You can probably get a much larger clear span with more conventional construction.

 

[jinman]

Do you want the roof covered in dirt too?

Egon and Dave, I sure would like to cover the roof with dirt and make it earth sheltered, but cost may prohibit that. I might have to settle for bermed construction where only three sides are covered with a conventional roof.

 

[6sunset6]

I have seen precast concrete roof structures backfilled with foam blocks and then some dirt. I think they will carry the weight fine. It's the cost that might be an issue. Call some precast guys.
It would be a great building.

 

[RobS]

It sounds very interesting Jim. Not sure about Texas, but up here in the midwest we would be concerned about humidity in an underground space. Even common basements up here get moisture/mold/rust in the summer without dehumidification. No way would I put a bunch of metal tools in an underground space unless it was properly conditioned. But again, things may be different down your way.

 

[johnnydel29]

My dad was a mason contractor for 41 years and I worked w/ him growing up. We did a lot of concrete work (too much).

The concrete w/ reinforced steel would be incredibly expensive, especially the labor. If you want to be safe, It would also need to be professionaly design by a licensed engineer - another big expense. However, it can also act as an awesome undergrown bunker that you can use during storms or a nuclear attack.

Awesome idea.