Underground Dome with Aircrete or Concrete or...?

Hi all,

I am interested in building a dome to then bury underground in the side of a hill (with an archway entrance on the southern side). This would be located in the desert southwest US.

I am not really sure where to start or what methods would be best. I'd like to keep the cost down as much as possible, and I'd like to be able to work on it mostly by myself, but also sometimes with my wife when she is available. Hence, I have been thinking about aircrete since it's lightweight, low cost, and probably easier to work with by myself.

I was considering building a frame of some sort (not sure what method), wrapping that in fabric, spraying that with aircrete to create a shell/form, and then cover the whole thing with rebar and concrete. But I'll be honest, I don't know what I'm doing. Maybe I'd build a dome with aircrete blocks and then cover with concrete?

What's the best method I can take in this situation? I know aircrete needs to be waterproofed, but I'm not sure how strong it is by itself to bury a dome.

Hi there!
The idea is interesting, and domes can be good shapes for dead loads (when shaped and built right), but what you are describing really would benefit from an experienced designer and builder. It would not be good to be buried alive. Even if you end up doing lots of the work yourself, having a sound plan is so important. Are you in a code-free jurisdiction? Is this meant as a dwelling or a food storage bunker? There are lots of questions that come to mind, but while affirming a super cool vision of underground desert living, I really encourage some serious design and planning. If DIY remains your goal, consider earthbags, perhaps. Kelly Hart has good resources, among others.

Best to you,
Mark
(I am an AZ PE and have done load calcs for basements, in case you wondered, and am really trying not to be discouraging, just clearheaded)

I agree that sandbags might one method to look into. You might also look into log roofs, such as are used in the wofati. I can't find any links right off, but someone else may be able to point you to those.

My biggest concern is that aircrete does not seem to be very structural. In other words, it seems to be designed more for insulation than for holding up a wall or roof. I'm not super familiar with it, but you definitely want someone skilled to verify how the roof is built. That much dirt and water needs some really good supports to stand up safely.

"Desert Southwest" and underground sounds like thermal insulation is not one of the primary factors in design, so I would not consider aircrete just for that. If it is not structural but would need standard concrete poured above it, that just sounds like extra work. What is your elevation, and how cold do winters get, and for how long?

To work on a dome mostly alone, I would frame up a supporting structure to receive units and hold them while mortar sets (if mortar is involved). Skilled masons build brick vaults freehand, but that takes long experience. If you want the strength of a reinforced concrete dome, building a wooden form would allow progress at your own pace with appropriately placed cold joints.

Here's two dome kits that you could check out. I've talked with both and they're all pretty cool folks. Very helpful.

https://www.dreamdomehomes.com

https://gaiadomesolutions.com/en/prices/

Ok, good thoughts.

I watched a few videos about aircrete last night and realize now that it's mostly for insulation and doesn't provide a strong structure, so if I go with an underground design, it might not be the best. I've done earthbag building before, and though it's very cheap, it's also very back-breaking to do alone.

We'll be at around 7000' elevation and the winters get quite cold.

J,

I would go with regular concrete. Please do not forget proper reinforcing - I would do at least rebar 1/2" on 8" grid and if the thickness of the dome is greater than 5" I would do two layers of such grid - outside- closer to the outside and inside, closer to interior. The rebars can be bent with large radius by some rebar bending company - they will have right equipment. If the dome is quite large, the rebars can be formed without bending - they will collapse under their own weight, but you would still need circular bars, perpendicular to the verticals. For larger dome, larger bars may be needed. Also more rebars as you approach the bottom of the dome.
With such a large structure you want to have continuous pour. Mixing it in some tiny concrete mixer will not make enough concrete quickly. Also, please remember to vibrate it properly - to remove air bubbles, encapsulate rebars and give nice finish to the surface.
Using CAD software you could model the shape and quickly calculate required volume of concrete.

Like Christobar says!

I did a fair bit of research into structure of domes a few years ago and I don't know the engineering terms, but the top takes the load and the nearly vertical struts take the expansion (holding its shape)
So in my case, a well cover design, concerned about snow load, I reinforced the top struts by doubling them up with longer connector bolts, and a really long one on top, in order to add a spire.
Mine is not buried so my first try uses two slightly damaged used commercial climbing domes bought dirt cheap, to get my measurements/ pattern that then can be multiplied by any ratio bigger or smaller to get the sizing I want for my own build.

Anyway the weak spot was the bottom struts -- if there is any heaving and rocks are finding their way to the surface as rocks will do, they can bend those struts especially at the point of connection (hubs).
My two slightly damaged domes make a sphere -- the access point being directly underneath, similar to an igloo.

As soon as you modify a section like a pentagon and put in a door, you weaken the whole thing considerably, but igloo style, if you access from underneath you can help retain structural integrity (think of mushroom -- thanks again to nature's ingenious designs that humans copy and tend to forget where credit is due)

When I get around to my second try, I will be using 1/2" rebar and oxy-acetylene -- Christobar, do you know if oxy is adequate for an above ground non load bearing application or ought I use arc? How about load bearing? I don't have my own arc welder, yet, but I do remember how to.

Myself I may very well do the rebar dome idea on the damaged south wall of my house, once I've gotten the load bearing problem resolved (half of the load of the roof). It's a very small hemlock house. Small is good! I want to install a half globe so it jutts out of the wall, and the top half gets high quality corrugated greenhouse plexy so I am very interested in your project.

I like this idea.

The Monolithic people say there is a dome near the Rio Grande that has been buried under 28 feet of dirt.

https://monolithicdome.com/invisible-dome-home

That's an amazing dome!