Underground Shop

[85blue4runner]

On the tube this weekend, i saw a show about underground and unusual homes around the world, many of which were made from commercial materials such as steel and concrete. So i got to thinking about a small shop of some kind made into a hill, especially in cooler climates, the earth would act as an insulator for both sound and temperature.

After doing some research online regarding underground and earth berm homes, along with some basic calculations, it seems that a small shop space can be built very cheaply, less than 5 grand in concrete, depending on your area. This covers side and rear walls and slab, all 6" thick and roof is 12" thick to support earth on top. These numbers are for a 30x30 shop and do not take into account interior walls, electrical wiring, etc., as those things should be about the same regardless of the type of structure.

I envision the structure as basically a concrete box with the front open for garage or bay doors and a bowed or arched roof for the best loading/support of the earth above. What I cannot seem to find is how to calculate dead load and live load on a monolithically poured concrete mass for a given shape. We all know that tubing, circles and spheres are some of the strongest structures on the planet as compared to squares or triangles, so it seems like a slightly arched roof would be the way to go, but I dont want 100,000 pounds of dirt falling in on top of me either.

The space would be very energy efficient and could be heated with a waste oil stove and a small AC unit if necessary depending on location, the space should stay in the low 70s year round. Standard power could be used as well as solar or a generator running on biodiesel or waste oil. The side walls and rear wall will be back filled with earth after being coated with a vapour barrier and waterproofing and polystyrene insulation.

I would be interested to see if anyone has built a structure like this or knows the calculations to figure loading on the roof so it does not collapse. If all else fails, guess I will find an architect, but i thought that I would try the powers of the PBB first.

thanks

jon

[D60]

I am NO help but I think it's a very cool idea!

Be sure to get the wall and ceiling height you want the first time around, ie probably at least 12' walls so you can add a two-post lift later if you want.

[desertsport]

where do you luive tht you have hills or mountains that you can do this to, Are they on your property???????

[85blue4runner]

where do you luive tht you have hills or mountains that you can do this to, Are they on your property???????

I am in the Atlanta metro area. Right now its just a design exercise/R&D. It would not be hard to find a good location for this, especially in the northern suburbs. You basically need a hill, rolling grassland or something of the sort that you can get a small excavator to and dig into the side of a hill or bank. Conversely you could pile earth around the building after its constructed but that may cost more $$. Trying to make this cheap and green.

Picture a hill like this /|X| with |X| being a block of earth and the front not so steep. The vertical bar to the right of the X is the back wall of the shop and you just dig into the hill. The shop goes into the hole and you fill earth around it. If the shop is 12' and has 3' of earth, you need a hill that is 15' or so, not that hard to find around here.

[PAToyota]

I looked into underground/earthberm housing back when I was in college. Did a couple designs. The thermal mass is definitely the ticket. For homes, the moisture problem is an issue. Not quite as big a deal for a workshop/garage, though. I'd look into precast concrete planks for the roof structure. By the time you'd set everything up to form a roof you'd save time and money just going precast. And the precaster will do all the design work for you as far as loads and such. Just work to standard precast dimensions and you're set.

[Rudezuk]

That is an awesome idea...

It would be nice to find some property to be able to do this :D

[indulf]

just make damn sure you get your ventilation straightened out...

[D60]

If the shop is 12' and has 3' of earth, you need a hill that is 15' or so, not that hard to find around here.

Wow, you really got me thinking. Please keep us posted if you pursue it any further. I COULD do this on my property. Scary........

[coachgeo]

Wow, you really got me thinking. Please keep us posted if you pursue it any further. I COULD do this on my property. Scary........

I once thought of burying aluminum shipping containers coated with Durabak. They were outer walls. Cement top. Your idea is the usual. Still though I would coat the cement wall that is against the dirt with Duraback as a moisture sealant before filling the earch back in around them.

[35xj]

that seems like a very optomistic price on materials. I payed 90 bucks a yd for concrete yesterday.

[85blue4runner]

that seems like a very optomistic price on materials. I payed 90 bucks a yd for concrete yesterday.\

thanks for the comments guys. The number that I used for the concrete was $70 per yard and was from a contractor friend, so maybe it was a little low. I have figured about well under 70 cubic yards for this structure and that is how I got the $5000. That does not count hired labour, rebar, forms, etc. Just trying to make the structure cheap and simple. I thought about the spray on liner too for water proofing and cracking, but I think that i would go with Bentonite instead.

keep the ideas and comments coming. I am taking notes...

[tennessee rockhumper]

my shop is under my house. my foundation is made of 9 foot tall, 10 inch thick concrete poured walls. back filled on 3 side with the garage doors on the end.

the poured walls are the shit, they are vastly stonger than corefilled block and my garage is very dry at all times. it amazed me to watch them put it up. they came in day 1 and poured huge, 3 foot wide footers right on top of the ground. day two they built the frames for the outside forms of the walls and suspended a big jail cell out of rebar bundles inside them, then put up the inside forms of the walls. day three they poured the whole damn thing with a concrete crane pump truck, in a matter of hours. a week later they removed the forms and poured the floor.

however, there is no way in hell to do that for less than 5 grand. i think mine was more along the lines of $12,000 and i didn't have a concrete ceiling that you need.

remember the nessesary dirt removal, waterproofing, french drain, gravel, plastic, back filling, and dont forget about 5 miles of rebar bundles to reinforce the concrete.

if you cant get to the top of the structure with a concrete truck, now you need a concrete pumping crane truck $$$$$!!!!!!

if you do it, dont forget to leave pvc pipe holes for electrical, plumbing, vents, floor drains, ect, ect. because once the concrete is dry it is a bitch to poke a hole through it. (i left out a hole and spent 9 hours drilling a 4 inch wide hole through it. that shit is 3000psi and full of rebar)

goodluck!

[85blue4runner]

my shop is under my house. my foundation is made of 9 foot tall, 10 inch thick concrete poured walls. back filled on 3 side with the garage doors on the end........ however, there is no way in hell to do that for less than 5 grand. i think mine was more along the lines of $12,000 and i didn't have a concrete ceiling that you need.

remember the nessesary dirt removal, waterproofing, french drain, gravel, plastic, back filling, and dont forget about 5 miles of rebar bundles to reinforce the concrete.

if you cant get to the top of the structure with a concrete truck, now you need a concrete pumping crane truck $$$$$!!!!!!

if you do it, dont forget to leave pvc pipe holes for electrical, plumbing, vents, floor drains, ect, ect. because once the concrete is dry it is a bitch to poke a hole through it. (i left out a hole and spent 9 hours drilling a 4 inch wide hole through it. that shit is 3000psi and full of rebar)

goodluck!

Thanks for the tips and the info, the shop sounds really nice. As mentioned before the 5k did not include rebar, pumper trucks, wiring, etc and I realise all that will have to be figured in. What I was thinking about is could you make a floor, a roof and 3 walls for 5 grand using traditional wood or steel framing.

Will have to include rebar prices when i get them, along with some other numbers. Trying to eliminate pumper trucks and the like and keep it simple.Also looking at natural fibrous concrete which eliminates the stone aggregate portion of the mix, lowers the portland cement content and substitutes recycled paper. This makes the concrete lighter and does not sacrifice any strength. It also makes the mix cheaper, because paper is essentially free from the dump or recycling centers.

cheers

[85blue4runner]

Back to the top for info on structural calculations for the roof panel covered with earth.

thanks

[Oxjockey]

Back to the top for info on structural calculations for the roof panel covered with earth.

thanks

6" thick walls? I'm no engineer, but my foundation's about a foot thick. I would think drainage would be your biggest issue, get the water away from the sides and back and top. Edit: Don't forget, you're not only supporting the top, you're trying to keep the dirt out <->

You'll have to excavate your area, plus about 4' or more for them to form and pour the walls. That's a lot of dirt.

[85blue4runner]

6" thick walls? I'm no engineer, but my foundation's about a foot thick. I would think drainage would be your biggest issue, get the water away from the sides and back and top. Edit: Don't forget, you're not only supporting the top, you're trying to keep the dirt out <->

You'll have to excavate your area, plus about 4' or more for them to form and pour the walls. That's a lot of dirt.

The excavation will not be a problem. I will have access to a large front end loader as well as an excavator. The 6" thick poured walls should be enough, but I can always go to 8 or 12" if necessary. A poured rebar reinforced wall is much stronger than a block wall or even a block wall with concrete poured into the dead space. That however is the reason that I am researching all of this and trying to do some calculations to see if this is feasible or not. On what type of structure do you have a foundation slab that is a foot thick? That seems abnormal to me. Most residential applications are 4 - 6" exclusive of footings or pilings. I guess I could just make everything a foot thick, reinforce the hell out of it and call it a day.. Hopefully some architect or structural engineering types will chime in here.

For waterproofing, the poured walls will be covered with an impermeable clay membrane called Bentonite. If the clay absorbs any water, it will swell and then its even harder for water to get past that layer. Tar based sealers will also work when applied in multiple coats to seal out water. The walls will also be insulated on both sides to try and keep condensation down.

thanks

[thelbz]

I'm no expert on pouring concrete structures. But a few years back at my old job we installed 3 of the biggest mills in the world and started with a hole 60' wide 80' long and 27' deep built all the forms on site and bent and placed all the re-bar (1 1/4" the smallest) and after it was all done it was roughly between 8-12'. And lets say it takes a little more know how than you think you apparently didn't look into it very far, you also have to factor in the cost of wall ties, coil rod, and wire ties, also you are going to have to vibrate all the walls to prevent any voids.
And depending on the mass of concrete you may have to have Fly Ash, Silica Fume,and some sort of retarder because the heat generated from the concrete could cause major cracking. Just some things to look into if you want it to last but it all costs a lot more $$$

[s_ontario]

Heres a interesting link to a house build can't see why this kind of design wouldn't work for a shop.

Would make a Great house on a lake you could have a view of the water and from the front no one would even know there was a house LOL

http://ourworld.compuserve.com/homepages/phil_reddy/TheBuild.htm

July was a very interesting build month

[Oxjockey]

On what type of structure do you have a foundation slab that is a foot thick? That seems abnormal to me. Most residential applications are 4 - 6" exclusive of footings or pilings.

For waterproofing, the poured walls will be covered with an impermeable clay membrane called Bentonite. If the clay absorbs any water, it will swell and then its even harder for water to get past that layer. Tar based sealers will also work when applied in multiple coats to seal out water. The walls will also be insulated on both sides to try and keep condensation down.

thanks

It should seem abnormal, my slab is only 2-4" thick. :flipoff2: If I were you, I'd plan on hiring an engineer for this. Don't trust an architect for a structural calc. Not saying they can't, but I imagine you'd want stamped plans.

Anything short of positive drainage may give you fits later. Think about what it'd take to fix that later.

[BlueEyeDevil]

Just build a metal building like the rest of us red necks. It will be about the same cost for more than 1.5 times the sq ft, and you can put lean-too on the sides or add on with ease.

[Travis Waldher]

do a search on "spancrete" for the ceiling.

Don't overthink it, spancrete can be had strong enough to park vehicles on... so I'm sure it can be had strong enough for earth and a potential vehicle.

[AprilzWarrior]

I once thought of burying aluminum shipping containers coated with Durabak. They were outer walls. Cement top. Your idea is the usual. Still though I would coat the cement wall that is against the dirt with Duraback as a moisture sealant before filling the earch back in around them.


Call me crazy but I actually tried this.... and it didnt work. Im no expert, but I gave it a shot anyway. It was not the top that caved... nor did the sides... it actually bowed at the sides. Realisticly shoreing should have been used on either side then it would have worked... I think LOL :laughing:

[James_Fendley]

that seems like a very optomistic price on materials. I payed 90 bucks a yd for concrete yesterday.

When I built my shop last year in WNC, I poured 47 yards just in the slab. 85blue,talk to a engineer. You would be looking at a 100,000 easy. When you pour overhead, all the rules change.

[co]

There is a house close to me that is built into a hill, but it has a normal roof on it, so it looks like a roof sitting on a hill. This would be much less $ than a poured concrete roof and still offer the benefits of a underground shop. My basement has poured walls and it never leaks and is a comfortable temp all year round.

[85blue4runner]

Thanks for all the ideas and comments. I spent about 2 hours doing some rough calculations yesterday and it looks like I am at least in the ball park on the walls and roof with a parabolic arch. An acute arch will take more work. I will definitely hire an engineer and/or architect before any building actually gets done. The whole idea was to keep it simple, green and maybe even DIY for most or all of the build if the engineering can be done by someone else. Then you just follow their plans. May need help to lay the rebar, the pouring of the slab can be done in a day with a group of friends and a 2-3 yard portable mixer. Same for walls and roof after forms are up..

Looked at prestressed engineered panels, like the spancrete referenced above and found that 12" thick x 4' wide x 20' long panel weighs about 8000 pounds, which can be handled by a Skytrak type lift. The panel is not arched so the majority of the load is a vertical compressive force on the side walls and exceeds 1000 pounds per square foot.

I could build a steel building or pour the walls and have a normal roof, but I was trying to do something a bit different, like the house linked above.

Thanks again

jon

[Pook]

Call me crazy but I actually tried this.... and it didnt work. Im no expert, but I gave it a shot anyway. It was not the top that caved... nor did the sides... it actually bowed at the sides. Realisticly shoreing should have been used on either side then it would have worked... I think LOL :laughing:

:smokin: sounds like one of the many grow ops in our mountians....

[AprilzWarrior]

:smokin: sounds like one of the many grow ops in our mountians....


HA... we store the ATVs and other crap in it... not into the funny stuff.


:D

[Albin]

"Cheap", "simple", "underground" and "don't want 100,000 lbs of dirt falling on my head" don't really belong in the same paragraph, much less almost the same sentence.

If underground building's and structures were "cheap" you'd find them homes and shops built everywhere.

Not saying it can't be done, because it has. It's just not going to be cheap.

If it is, it'll be a deathtrap, assuming, of course, it gets approved.

My .02.

Al

[DownNDirty]

If you don't live in a place that you can do this, why not build the hill. The main point to an underground stucture is to cover all the walls that aren't facing the sun with as much thermal mass and insulation as possible. Theoretically you could build the structure and then bring in the dirt to make a big hill on the backside. It would be really fun to tell your friends you would love to come out an play, but the wife says you have to cut the grass on the roof first.

[PAToyota]

If underground building's and structures were "cheap" you'd find them homes and shops built everywhere.

Can't agree with you after having done the research. Big reason you don't see more underground structures is because people have this hangup about how it would be "like a basement" and think cold, damp, and dark.

Yes, you'll pay more for the structure but then again you aren't paying for the exterior siding and such and you're saving money on heating due to the thermal mass.

[Albin]

Can't agree with you after having done the research. Big reason you don't see more underground structures is because people have this hangup about how it would be "like a basement" and think cold, damp, and dark.

Yes, you'll pay more for the structure but then again you aren't paying for the exterior siding and such and you're saving money on heating due to the thermal mass.

Wrong. The reason you don't see more underground structures is because it's not cheap. Period.

If it was cheap, people would overcome the "cold, damp..." crap in a heartbeat.

[D60]

There is a house close to me that is built into a hill, but it has a normal roof on it, so it looks like a roof sitting on a hill. This would be much less $ than a poured concrete roof and still offer the benefits of a underground shop.

Not so sure about that........most of your heat loss is thru the ceiling. I think if you were doing this, it makes the most sense because of the insulating properties, and in order to maximize that you definitely want the roof covered in a good amount of earth.

I dunno, it just doesn't seem worth the effort unless you can put all but one side underground.......

[coachgeo]

....I dunno, it just doesn't seem worth the effort unless you can put all but one side underground.......

I thought that was exactly what was being proposed! All sides earthed but one.

[PAToyota]

Wrong. The reason you don't see more underground structures is because it's not cheap. Period.

If it was cheap, people would overcome the "cold, damp..." crap in a heartbeat.

Guess you've researched it and know all there is to know... :shaking:

[jeeplord]

do a search on "spancrete" for the ceiling.

Don't overthink it, spancrete can be had strong enough to park vehicles on... so I'm sure it can be had strong enough for earth and a potential vehicle.


It's engineered for you, all you do is crane it into place. I'm thinking you'd need 8-10" thick walls and 24" footings (by our norhtern codes). But you could park on top of it. In fact I've done buildings (commercial and residential) with over/under garages utilizing spancrete.

If you are building a proper garage, you should have a 6" fibercrete slab, cut in 10x10 squares with #4 rerod in a 2" grid

Run your heating element (fluid or electric) in the sand under the slab for maximum efficiency. We've even done weirsbo in the wall slabs of some buildings.

The problem you have is too many variables and options.

[chowderhead]

you should look into the post-tension system for your roof deck also you said you wanted to do a mono pour i myself think thats way to much wall to even try. i would go for 1' x 2' spread footing with #5 bar and the walls i would go with a 8'' with a 12'' spacing on your vertical and horizontal steel mat using #5 bar and for the best looking wall use 4' x8' 3/4'' MDO plywood with cone ties

[saf-t scissors]

Not so sure about that........most of your heat loss is thru the ceiling.

Maybe in an old house with no insulation.

A modern house with R-38 upstairs loses most through windows, doors, and walls.

[saf-t scissors]

May need help to lay the rebar, the pouring of the slab can be done in a day with a group of friends and a 2-3 yard portable mixer. Same for walls and roof after forms are up..


I would not recommend trying to pull off a pour like this with just some friends and a portamix. If you've got some friends who are contractors with significant structural concrete experience, then maybe. ;) The portable mixer is just asking for trouble, tho. You might get away with it in November.... but you want to be able to pour 12, 15 yds at a shot, and have the next truck on the way ASAP.

Just for fun, look around for photos of the underground hangers they built in England during WWII. Big, parabolic roof, open on one end, etc. Pretty similar to what you're describing, I think.

It's a neat idea, but I think what you're proposing is a lot more difficult than you're thinking. It's certainly going to cost a lot (lot!) more than what you're thinking. You can definitely do it above ground, stud framed, with brick veneer, insulation, and sheetrock inside for less money.

Concrete itself is cheap, but there's a lot of labor involved. And this is not something I think even a well-qualified DIY homeowner could undertake. I've seen too many perfectly qualifed professional contractors screw up easier pours than this.

[bkfj55]

just my free two cents...

use ICF (insulated concrete forms) and be done with it. Yeah, building into a hill sounds neat, but it is gonna get you lots of problems as mentioned in the previous posts. You're gonna need atleast a 10" maybe 12" thick concrete wall. The higher you walls, the more reinforcement you're gonna need. If your roof doesn't support the inward thrust from the top of the walls, you're looking at a cantilever retaining wall, and then you're gonna get even more rebar in the wall...A good rule of thumb is one inch of wall thickness for one foot of wall height...

I'm not a professional engineer in your state, but I am one in virginia, west virginia, and maryland ;)

bk

[tennessee rockhumper]

May need help to lay the rebar, the pouring of the slab can be done in a day with a group of friends and a 2-3 yard portable mixer. Same for walls and roof after forms are up..

.....they poured 23 huge truck loads of concrete into my 3 walls alone. you will have a heart attack and die doing that with a portable mixer. i dont think you can even attempt it with homemade forms either, they would explode under the weight. then you would have one hell of a mess.

after actually building a poured wall structure, i feel very comfortable telling you it is definately a stronger, more efficent, dryer way of doing this. but i had to do it because of the type house i built and the land around my house. your savings on heat will not ever make up for the extra money spent in building materials.

call brandon at north georgia poured walls and let him run you through it. 423 870 3023