Natural Building Blog

Earthbag Building & Other Natural Building Methods

Earthbag Fortresses and Castles

Baku Fortress

Baku Fortress


Alnwick Castle

Alnwick Castle

No one has built an earthbag fortress or fortified castle yet to my knowledge. I’m just throwing it out there as a possibility. Building something like this out of earthbags would be much faster than working with stone, and certainly less expensive.

If this seems like just a fanciful thought, go back through some previous blog posts for background information. Tamped earthbags are comparable to rammed earth, which can last thousands of years, as explained in my blog post Ancient Rammed Earth Structures.

One good option for extremely durable and/or fortified structures is building with geopolymer. Geopolymer is man-made stone consisting of low cost natural materials such as loose limestone, diatomaceous earth, fly ash or rice hull ash, and low cost binders. This is how many scientists now believe the pyramids in Egypt and many other ancient structures were built. You could use geopolymer in earthbags, cast in place with forms, or make geopolymer bricks or blocks. About 20 geopolymer products are already on the market if you prefer off-the-shelf solutions. All these options are discussed on my Geopolymer House Blog. If you’re short on time, here’s a brief Geopolymer Summary that provides a brief overview of some options.

Baku Fortress
Alnwick Castle

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15 Responses to “Earthbag Fortresses and Castles”

  1. Steve says:

    We posted some sandbag towers and designs from real ones over at

    http://www.utopiasprings.com/gallery.html Nader and I discussed this at some length. A 2 in 10 batten is required for real stability, wind and seismic loads.
    So a 12 foot diameter tower base, tapers to 10 feet diameter at 10 ft high, 8ft diameter at 20 feet high, enough for a large water tank, like used with aeromotor windmills. These towers can then be corners or central to designs, like spirals.

    I see all sorts of attempts to make sandbags into regular freemasonry, which they were never designed for, all that plumb-level-square stuff. Really solid natural looking walls etc have waves in all three dimensions, from seashells to national monuments in Utah. Sandbags are ideal for building in full biomorphic styles.

    See pics of Utah sandstone monuments to see the “waves” and arches that give sandstone enormous biomorphic strengths. In fact, seashells have even more ridges and corrugations when in high surf zones. These also allow for easier growth of plants, vines etc to complete the structure in harmony with the gardens around it.

    For really extreme corrugations, see Termite Mounds !
    these earth builders are so sophisticated scientists are still studying the details, like interior convection, air flow, micro environmental shading effects etc.

    Some of my favorite biomorphic designs are Foraminifera and Radiolarians.
    Forams create wonderful homes by adding on a larger roon part way around,
    and these have been discovered in earliest stone homes in S. Africa now.
    http://www.bibliotecapleyades.net/sumer_anunnaki/esp_sumer_annunaki35.htm Im not a big fan of his explanations, but the pics are great !

    Good Building

    Keep Diggin !

    Steve

  2. My kids have been asking for a castle so we can have lots of kids at our child rescue center we are building with earthbags next year….if we could make an earthbag castle that would be awesome! Let me know when you have some workable plans…also offer to be testing site for putting one up here in Honduras :)

    • Owen Geiger says:

      My castle design is huge — about 80′x100′ with four structures. But reader’s could study the plans and create something similar on a much smaller scale. This could include a tiny castle for kids (like a play fort).

      • We are looking to build 2 houses that are around a 50″ by 50″ footprints, each to house 11 children and a Tia. So its not out of the question…looking forward to seeing your design.
        A kid fort would be really fun also. We have quite a few very large rocks on the property we want to build around.
        Do you have plans to actually build the castle?

  3. Peasant says:

    I would really like to know how well an earthbag fortress will hold up against a boulder flung by a trebuchet.

    • Owen Geiger says:

      And the risk of that happening is…. what? (Just kidding.)

    • Kat says:

      Depends on the trebuchet! :-) No, seriously- the trebuchet design is quite scalable, from tabletop tennis-ball throwers to Philip II’s “Bad Neighbor” and Edward Longshanks’ “Warwolf”.

      That said, I don’t see any manmade, aboveground structure doing that well against 1500kg stones being hurled at it… I think that’s where the active defenses come into play.

  4. Lisa Jarhead says:

    Ha this is a great idea! Before you know it there’ll be 20 earthbag castles in the works all over the world! Seriously….awesome. I’m going to have to read up some more on geopolymer; that sounds interesting.

  5. Kat says:

    When I first saw the Gothic pointed arches for window and door openings, that’s where I immediately went. I’ve been having trouble designing something that keeps the castle-ish feel and yet is only one or 2 stories high.

  6. weezul says:

    In truth, I plan to build a tower in the next couple years, using a mix of geopolymer blocks and earthbags. Just need to find some land and save up a bit more. Thank you for all the great information you provide on the topic!

  7. Okay, so we turn a CORGANIX Hybrid home (ISBUs combined with Earthbags) into “Gulag Geiger…”

    All we need to do is determine the height of the turrets and figure out where all the lasers and landmines will go… ;)

    … because Amway salesmen can be very persistent.

    I already figured that building a CORGANIX Home would entail an additional hard look at it’s anti-ballistic properties. It’s actually for that reason that I’m considering actually running the earthbags across the (previously) exposed ends of the container, to “negate the perceived weak spot” in that 14 gauge corrugation.

    While it will stop most weather driven events, it won’t stop an AR-15 round. The earthbag walls however… that’s another story entirely.

    We can call this project “The Bubba Bunker Project”.

    • Owen Geiger says:

      First of all, it’s NOT a gulag. You see, the good guys are on the inside.

      I’m sure you could scale down the idea and create an appealing fortified home with a tower or two. Mmmm, I’ll have to think this over some more.

      Plugging in an ISBU pre-built core is another great option.

      Maybe put my Survival Shelter underneath. http://earthbagplans.wordpress.com/2010/09/20/earthbag-survival-shelter/ (if it’s not a flood zone)

      Add some escape tunnels, crocodile filled moat and a few other goodies and those pesky Amway salesmen will think twice before bothering you.

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