Aircrete and earth-berming

  • One of the things I read frequently about aircrete domes is that they resemble hobbit homes. But Bilbo (and Frodo) Baggins lived in a hole in the ground. Earth sheltered homes offer some significant advantages.

    My point? Anyone have any experience with using aerocrete blocks in conjunction with earthberming, to create a mostly-earthsheltered dome or elongated arch structure?

  • Workshop Instructor

    I've been researching it and it seems the perfect material being that it has insulator qualities but lacks the thermal mass that earth has. A complimentary relationship to build with. I intend to try it....

  • Little Dragon Tamer

    I have not seen or heard of this being done yet, but this is exactly what my parents want me to build for them so I am particularly interested in this conversation.

  • Do keep us apraised, Ignachos.

    My concern is with loading. How will the aircrete hold up under the pressures of being buried?

  • Workshop Instructor

    i wouldn't bury it. My intention would be to berm the house. I want to berm the periphery with earth bags first then french drain with shale in between home and bags. Berm using local earth leaving 1/3 or 1/2 the home exposed to plant a light earth dependent moss to the top of Dome for more shade. Water with a light timer and circular soaking hose at skylight and parimeter of berm.... Any recommendations?

  • Little Dragon Tamer


    My concern is with loading. How will the aircrete hold up?

    The aircrete dome of the common Domegaia design may hold up just fine buried. Consider that while there would be additional weight on top, there would also be additional support on the outside. We can increase the ability of the dome structure to withstand downward force (weight of the dirt from above) in three ways that I can think of. 1. Use thicker blocks (we normally use 3.5" thickness). 2. Place the equator of the dome at ground level instead of at 3' high. 3. Use a catenary or oval dome shape instead of a simple circular dome shape.

  • Workshop Instructor

    Thanks! I'll consider that... Good advice! I'm thinking that burying it partially would take allot of the downward weight out... The force would come from the sides which I feel a dome has plenty of strength. The point of the earthbags would be to reduce earth and dome contact also by acting as a retaining wall... the roof would have a succulent of sorts that requires little earth....

  • Workshop Instructor

    This post is deleted!

  • Workshop Instructor

    Anyone have an idea if the glued fabric cover on the exterior of the dome can be used as a waterproofing membrane for berming the dome? I would probably apply a sealer also before burying it, but would the fabric and glue alone be enough? Just curious?

  • Little Dragon Tamer

    The "Fabric Glue" recipe that we use is:

    6 parts cement
    2 parts water
    1 part concrete bonding agent

    It does create quite a water resistant shell on it's own. However, before burying or berming I'd want even more confidence. Have you heard of Impervizante roof paint. I hear it's very popular in Mexico.

  • @zander said in Aircrete and earth-berming:

    Impervizante roof paint

    I am googling and trying to find info on this product to no avail.
    Do you have another term or brand name?
    Thanks, this gringo is too far north to be familiar with such a product!

  • A topic after my own heart!
    I am not an engineer and have NO experience with Aircrete, Domes or Ferrocement
    In my head (which can be a dangerous place to visit)
    over the last month (which is when I discovered Aircrete)
    I have been thinking they would all work synergistically well to go underground!
    Build your Aircrete Dome then put a strong coat of Ferrocement over it.
    "Strong" is the operative term here to define.
    I am thinking that there are Ferrocement Underground Structures and some even in the shape of a dome.
    Aircrete would I guess just offer the insulative properties and ease of building the dome.

    For extra strength maybe build a dome first out of electrical conduit (or other struts of choice). Fashion a mold to build triangle blocks of Aircrete mortared together with Ferrocement supported first by the dome grid, then covered with a Ferrocement strong coating fabric, maybe even thicker than normal (whatever those Ferrocement Underground Dome builders have already calculated). You could also have the gaps in the blocks large enough to tie all the gaps together with rebar.

    Ok, thanks for letting this neophyte get all this off his chest!
    Comments are anxiously anticipated!

  • Little Dragon Tamer

    @jwboing I imagine that an aircrete dome would provide a lot more than insulation even if underground. The way I figure it, the pressure of the soil would work together on all sides to hold the dome in place. The aircrete dome would be the form around which one could build an earth dome. In other words, the soil itself would merely add to the strength.

    I am no engineer, and have no experience building anything underground. This is merely what feels correct to me.

  • Workshop Instructor

    Your spot on Zander! Yes, the structure would get stronger...

  • I built an earthbag home with intersecting vaults of ferrocement as a roof. I’m still experimenting with aircrete- did not want to use foam because it’s been implicated in the deaths of firemen and occupants due to the hydrogen cyanide gas that’s released when the stuff burns. I’ve been going for fireproof as opposed to flame resistant. No fire district where I live.
    I’m on well water and the water is hard which seems to be causing my attempts at aircrete to fail so far...
    In terms of a hobbit house that can actually heat and cook itself with the sun and earth, something resembling an earthship would be good- greenhouse for food and to heat the home without other inputs even in harsh winters. But tire wall construction is very laborious and I’ve found with earthbags I need to cover the bare bags so in effect attach stucco wire to both faces. It would be far easier to build two ferrocement walls with a gap and backfill / tamp earth into place. Or simply start with a ferrocement shell and bury it- ferrocement is famously strong. I would insert photos but that feature isn’t working with my phone. I’ve got many photos of the construction process at my non commercial, personal blog:

  • Great info and blog. Looking forward to following along!

  • @zander

    Has there been any sort of engineering report on aircrete? I’m getting my general contractor license and I know that I will have to objectively show the load bearing capability of this material. I will be building my houses underground. Thanks.

  • My guess is that u can do it with the right waterproofing plastic, u can look for green roofs materials.

  • @ignacio-dhome THANKS FOR THE REPLY!!!

  • Workshop Instructor

    @jwboing I know that alasteritameric paints are very flexible for roof waterproofing. They are commonly used for porches, roofs, and marine application. My main goal is to create an impermeable skin over the dome that will not crack, mold, or absorb. I have used this product several times which have held up over ten years. Granted, these are water shedding applications like roofs and decks. I would apply a fungicide as a preventative to the mixture to prevent mold if I am to bury it. I am currently on a project that I intend to use it on. It may be a while so if anyone has any experience below grade with this product please share.

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