Sofati? Superadobe OFATI

Hey there!

Im sorry for any grammar/punctuation/capital mistakes and laziness. i am writing this from my mobile phone on a 6 hour boat journey between two greek islands. there is a big chance i will settle land in greece, and as i traveled around for the past week or so i observed and noted many of the features in the landscape. I will need a house, and would like to build a wofati. the cheapest and easiest way to build a wofati would indeed be using pine, but greece has too little forest cover to have a properly functioning watershed as it is. there is no excess to build with, at least on the islands. i am following the wofati builds closely, but until now as a lurker :p

Taking a lesson from the local style, before the concrete boom, would lead me to build with rock. but drystone walling is expensive in all three dimensions of the project triangle (material cost, labour, time). good natural stone is still more costly than gravel.

Ive done some research into this field before and believe that perhaps superadobe might be the solution here.
the domes and arches should have the structural integrity i am looking for, the sand/gravel is local and freaky cheap. quite possibly 90% of material is onsite like in the wofati, if i would have a way to seperate sand and rock easily after excavation.

Another thought has been to use gabions for the main structural walls. A lot of the manual labour involved in the superadobe could be avoided like that. fencing and filling the gabion cages could be limited to 2 people. these walls would then be the basis from which to build the arches to span hallways or square rooms. or in case of round spaces, the domes.

the wofati concept of layering would still apply except that the earth layer between the first and second layer of poly is variable. because the domes are curvy rather than the flat gable roof of the wofati, the dry/ATI earth layer would be thin (the minimum 4in) in some places and rather thick in others (some meters). i dont really see a problem in this, the umbrella will still cover all and create the thermal mass. ofcourse the wet earth layer will still cover the umbrella.

one thing that comes to me as i write this... normal superadobe structures are notoriously hard to seal properly against weather. imagine using any kind of plaster on your roof, the tiny crack that means nothing on a wall, spells doom for an arch or dome roof. using superadobe this way would circumvent that problem completely. correct?

the only problem i see now is the F in wofati. superadobe is cheap, but its not freaky cheap. the cheapest roll i have found so far is 1500$, for a 3 bedroom home. i cannot imagine uv proof(ish) polypropyleen is that expansive. am i paying for a brand here?

so, any thoughts? i have build with superadobe before, so know its pros and cons. it seems like i at least evade some cons (weatherproofing, what to do with the stones you excavate, rainwater pooling around the foot of the house) and utilize all of the pros (structural integrity of domes and arches, ease of construction, local materials, etc).

please, pick it apart! would the domes stand up to the weight? is superadobe the right choice? what do i overlook? any flaws picked out now will improve the general design!

With warm regards and looking forward to your feedback,
Berry

Hi Berry,

It's been a few years since your post, but I just came across it now. This sounds like a very interesting and practical way to build in Greece without using the concrete that is so common there. What ever happened? Did you buy land and build something? I think that your gabion idea has lots of promise, but I'm still researching that avenue myself.

Cheers!

Tom

Thanks for bumping the thread. Berry makes some interesting proposals.

I like the idea of using gabions for the walls. If you lined them with a geotextile, you could make superduper adobes (just use the dirt as is -- no need to separate out the stones).

I think that a superadobe dome would have sufficient mass to forego the need for much more dirt above the waterproof layer -- no more than what is needed to sustain a green roof, and that could be very lightweight with soil amendments like expanded clay or shale, charcoal, perlite or vermiculite.

My father made a simple screen out of two by sixes and hardware cloth to separate small stones and gravel from the silt, clay and sand, then he washed the sand to make grout and used the gravel and sand in his concrete mix. You can also make a frame to hang the screen to make it easier to shake (my dad just used shovel to move the dirt). If you look at video of archeology or paleontology worksites you will see different designs to give some ideas.

What would be used for the insulation layer? Expanded/foamed glass? Perlite? Straw, sawdust or wood chips? EPS or closed cell foam?

Hi Andrew,

Thanks for keeping the thread going. Adding a geotextile inside the gabions so that they can be filled with soil is exactly what I had in mind too. I agree that these would be super duper adobes. I'm curious if anyone has any reasons why these would not make suitable building elements? I'm aware that tall walls may need internal bracing posts. Also, that if they're used as a retaining wall in an underground building, a geogrid should placed between each layer and then imbedded hozontally in the embanked wall (as a deadman brace). Other than these caveats, I can't see why these wouldn't be amazing to build with. I do intend to experiment with these ideas after my land purchase in April.

I'm a huge fan of domed and vaulted structures. I'm not sure how gabions could be used to make them safely without using a Lot of cement. You could make a stair step arch/vault by offsetting them slightly towards the center as you placed each layer in two parallel rows. Is that what you had in mind?

I've sifted a lot of dirt with screens, such as the ones you describe. You sound like you were lucky to be raised by a clever and resourceful father.

That's a good question about insulation. My thought was that if the super duper soil gabion adobes were three feet thick and had tough clay and/or lime plasters protecting them from wind and water, then they wouldn't need any insulation. They would have enough thermal mass to resist swings in external temperatures. I live in the fairly mild climate of the central Texas Hill Country, though. If insulation was required, for a particular climate, then I would be drawn to an all natural insulation, such as perlite , rock wool or pumice.

Great Questions! Keep 'em coming

Tom,

I think the OP's intention was for the gabion to serve as the wall only, then put the super adobe dome or vault on top of that. I think he intended to use rocks, separated by picking and screening, to fill the gabions and the screened dirt would fill the tube or bags. A gabion would not make a good vault or dome without some clever engineering and expense.

Gabion walls could be used by themselves, but, within the context of wofati design, the gabion becomes a structural element within the insulated mass, forming a retaining wall to protect/define the interior space. I just noticed that you were the OP on the House Dam discussion. I never was good at remembering names. Anyway, as I mentioned in your thread, gabions could be used to provide the vertical wall on the living space side. A quick review of gabion walls showed internal supports for tall thin walls. A thick wall may not need those supports, but the size of the cells may need to be played with to minimize distortion, as the dividing partitions apply tension. If properly tied into a larger mass, as you described, a thin gabion wall would need no further support.

A discussion of gabions should mention that, like superadobe and earthbags, while dirt is cheap, there is an expense in purchasing/acquiring the fabric/mesh you are putting the dirt in.

Hi Andrew,

Thanks for the clarification and your diplomacy. I just went back and read the original post and realize that the original poster suggested domes that were made of superadobe. I get it now. That would make sense and even seems workable. As the OP mentions, waterproofing them and cost are the two biggest factors.

My partners and I are currrently making vaulted roofs and domes (bovadas) in Texas using compressed earth blocks that are extremely strong. They're not dirt cheap either, but very beautiful.

I'm still learning about wofati design and how the insulation integrates with it. I'll read up more about it to see how best to integrate insulation.

I'm not the OP for House Dam post. That was a different Tom (Tom Harner). I just watched the video on it and I'm not impressed with that design. It seems dangerous, unless the walls are shored up with posts or gabions. I agree with your suggestion in that post that the interior walls should be sloped to an appropriate angle for safety.

I'm working on some gabion wall systems designs in Sketchup now. I'll create a new thread to display them and ask for critical feedback.

Thanks!

Tom

Wow, I really am bad at names. Are you using any of Gernot Minke's techniques in your domes and vaults? I know he says his compressed block domes are earthquake resistant, but I still have a hard time believing it. Do you use anything in your blocks to lighten them, like vermiculite or expanded clay?

Minke designed a really nice straw bale dome (needs a proprietary bale trimmer), but he doesn't seem to be too keen on straw anymore because of moisture issues. I don't know as moisture would be a problem in arid or semi-arid climates, but Northern Europe certainly could be problematic.

Hay bale vaults came to mind when you mentioned vaulting the gabions, as some bale vault designs use reinforcement mesh as their compression matrix, so, it may still be possible, but again, you need to get the engineering right.

Hi Andrew,

Gernot Minke is a distinguished leader in our field and we certainly are a fan of his. My partner has had the occasion to meet Mr. Minke at an earthen construction conference several years ago.

My partner has built numerous compressed earth block structures in earthquake prone areas, such as Haiti, but he has avoided domed and vaulted roofs in those regions. The wall system is rock solid in earthquake zones, if built well.

The blocks are heavy and we like them that way. They have more thermal mass and perform a key climate control feature, breathability of the wall. A 10in x 14in x 3.75in block is typically 35 lbs (US). Adding vermiculite or expanded clay would likely have a detrimental effect on their strength.

We've seen numerous issues with straw bale structures, such as mold, rodents and cracked plaster, just to name a few. We try to steer people away from them, but understand that they have a big following in the sustainable building movement.

I'm really enjoying this thread and am glad to have found a kindred spirit that is knowledgeable in numerous alternative building techniques.

Cheers!

Tom

Getting back to gabions and liners, here are some questions:

What is the expected life of a geotextile liner?

Would the gabion and liner stand up to the soil being compacted?

Could you use foamed loam in a lined gabion arch or dome?

What would be the best way to seal the surface of a stone filled gabion? I recognize that some would want to preserve the aesthetic of the stone face, but without grout or mortar, it makes a great hideout for vermin. I suppose you could do a kind of slipform stone masonry, using the gabion as a sacrificial form, or put a veneer over the gabion.

Hi Andrew,

I'm sorry I dropped our thread for awhile. Life gets in the way sometimes

I found that there's a wide range of weights and types of geotextiles. Some are woven and others are not. I ordered some non woven heavy duty geotextile and it's good, but the woven type seems much stronger. It also depends on how they are used (or abused). The article at this link says that they can last over a hundred years, in some circumstances:

http://www.infogeos.com/files/news/document/G37.575.pdf

The compaction of soils in gabions is something I'm going to start testing next month. I've already built my prototype.

I've never worked with Foamed Loam, but I know that Gernot Minke's talks about it in his book. It's really cool idea, but I would definitely want some steel or basalt reinforcement for arches and domes. Have you ever worked with it? How strong is it?

I'm looking into ways to seal the surfaces of gabions. I'm interested in trying to find a way to use bentonite clay plasters. These form a waterproof barrier that are self healing. I've found a few resources that talk about them, but I don't have direct experience with them yet.

Let me know your thoughts. They're always greatly appreciated.

Tom

Hi there!

My apologies for letting this horse die and then kicking it

It was indeed my idea to create the stuctural walls out of gabion meshing, then finish the roof off using superadobe domes or vaults. Because the cheapest and most widely available material that could become a gabion is a rebar wiremesh, the layouts I am playing with in my mind are using straight lines. I know rebar could in theory do curves, but my knowledge of structural integretity is too small to actually go into it and do domes/curved walls with confidence. I was thinking along the lines of a Hogan, an Oehler structure or a wofati shaped building. Keeping the wall sections to the standard size of wiremesh (what is it, 2 by 3 meters?) seems logical to me. If my research proves me right, you can do hectagonal and octagonal (sp?) domes using superadobe. Or transition from octagonal into a circle into a dome.

I have a few questions to answer and also to ask. First by Andrew Parker:

Getting back to gabions and liners, here are some questions:

What is the expected life of a geotextile liner?

Anything that is made out of polyethyleen or epdm can be expected to last indefinetely as long as it is not exposed to UV radiation. On the outside of the gabion this would be a minor problem as it would end up covered in dirt. On the inside it might create trouble for any kind of render to stick, it is a matter of what fabric is used and what kind of render you're trying to apply. My experience with lime plaster tells me that it could be alright to render a rough fabric, but anything close to earthbag/superadobe might need a basecoat of something else first (cob?). But to be honest, my experience comes from rendering cob and straw, not superadobe like fabrics.

Would the gabion and liner stand up to the soil being compacted?

As long as you're not trying to compact it with one of those compactors used in paving sidewalks I think you'd be fine. The video posted below is of someone making a compressed earth wall using one of those machines and they were using a system normally used to pour concrete to prevent the sides of the wall from buckling. So I assume that just using rebar mesh would allow too much play for more than regular compaction.

Could you use foamed loam in a lined gabion arch or dome?

To be honest, I have no idea about this exactly. The main reason for me to think without the use of foam insulation is that I expect to be too warm in Greece. Insulation might seem like something one would want in a colder climate, but with summer temps going up to 50C and winter temps staying around 5C I expect that we will need no insulation (Athens dipped 1 or 2 times below freezing this whole winter). The 17C underground temperatures that Oehler talks about seem like a perfectly adequate temperature for living year round.

What would be the best way to seal the surface of a stone filled gabion? I recognize that some would want to preserve the aesthetic of the stone face, but without grout or mortar, it makes a great hideout for vermin. I suppose you could do a kind of slipform stone masonry, using the gabion as a sacrificial form, or put a veneer over the gabion.

My first impulse is to go with Oehler's and Wheaton's design. Which is simply to leave the structural material to be exposed. I actually look forward to seeing the combination of rusty metal and raw stone. If one would choose to go for a smaller sized stone though, a fabric might be needed to contain it in the larger rebar mesh structure. If that's the case, a lime plaster seems in order. Grass or another kind of locally abundant material could be added as a layer between the geotextile and the rebar to provide a good hold for the plaster? I've also considered the use of carpet... carpet is one of those impossible to repurpose/recycle waste materials that might be around in copious amounts. If added between the rebar and the geotextile, it might make a nice baselayer for a plaster. It might also be a good candidate for protecting the polyethyleen from being punctured.

Another option I have considered, provided there is adequate natural light in the house, is to grow Ivy (Hedra Helix) on the walls. Or any other kind of shadeloving evergreen that is. The nice thing would be that you end up living in a completely leafy nest. The nasty thing is that a plant covering your walls and roof might make quite a mess inside. Airquallity inside the house should be amazing!


About the vermin. I expect to live with vermin, it is simply a fact of life in my opinion... keeping apropriate colleagues (pets) around and making sure there is no food exposed, should reduce their nuisance level to a minimum. Walls of any kind are a niche that is utilized as living quarters, I don't presume layers and layers of mortar will stop anyone from living there.... But that's my two cents. Also, I'm not bothered too much by mice or birds or bats, I think of it as a blessing to have other creatures joining me in 'my' house. Right now there's a Robin nesting in my strawbale walls

My own questions come down to these:
Tom Taber, in your post you speak about a geogrid being placed between layers... what do you mean with that? And on a related note... what is a deadman brace?

Also, considering superadobe and its related forms might make the strucure deviate too much from the original wofati design. What about just using gabions for the walls and then finishing the roof off with regular woodland materials?
OR, if you were to have access to copious amounts of other materials, some other kind of roofing material. I've been thinking of shipping containers. I know that in large parts of the world shipping containers are simply left and sold off for scrap metal prices (sometimes even given away, though that might be changing). I could imagine stripping the corrogated metal sides from the containers and using them as a roofing material. And perhaps the beams that are left over as horizontal roof supports? Like I said, my knowledge of engineering is limited, but I can imagine that it is a very easily recycled building material and if properly supported it should last generations. It would not need to be watertight, just able to support the weight of some soil (I believe 18 inches is what I've heard mention).
http://www.panamashippingcontainerhouse.com/cutting-metal-making-a-wall

Your thoughts?

Hey Berry,

Thanks so much for rejoining your original conversation and for all of your great information. I feel lucky for having met original thinkers and inventors like yourself on Permies.com

A deadman is an anchor that extends into the back fill and has a flat surface that's parallel to the retained wall at it's end. They can be formed from a cable that has something like a shovle blade on it's end, or it can be made from wood or concrete. Whenever you build a retaining wall, these types of anchors must be incorporated to resist hydrostatic and other lateral forces on the wall. I've include some photos below to make it more clear.

Another alternative, when building with gabions, is to place a sturdy geo grid mat between each layer of gabions and bury it into the retained soil as you back-fill it.

Hopefully this helps clarify it.

I really like your ideas about using carpet at a backing for stucco and using shipping containers for spanning roofs. I've looked into building with shipping containers quite a bit and they have lots of drawbacks, but this is an idea worth investigating more. When I've looked into buying them they have typically run $5,000 - $8,000 USD, but I'm sure they're much cheaper in large port cities. They do loose significant structural integrity once they're cut apart, but the corrugated sides could make sturdy paneling for roofs.

Just returning to using gabions for the walls. Rather than using geotextiles or similar have you considered combining cob with the rock fill? This is similar to a technique used in the mountainous parts of the Indian sub continent called dhajji dwari. http://www.world-housing.net/tutorials/other/dhajji-dewari

The cob holds the rock, provides infill to prevent "guests " and drafts and would add mass. Depending on whats available onsite this could be extremely cheap. They would be very safe from quakes as well.

The big question is how long will the gabions last?? If you rendered the gabions with cob, thus keeping them from the atmosphere and water, I would imagine they would last a long time.

Berry,

Sorry I missed your response. The notification system here is not the most consistent.

I did a quick online search on foamed loam and found a copy of correspondence from Gernot Minke, dated 2006, in which he states that foamed loam was not working, in practice, so I guess we can eliminate that from the list of possibilities, for now.

I like your hexagon idea. You should be able to make the transition from polygon to circle fairly simply with superadobe. If you can combine some arches with the hexagon, you can build a cathedral. I am trying to envision how to make a gabion arch, using mostly the same material. I don't think I would trust superadobe or earth bags to make the transition from barrel vault to dome.

If you attach chicken wire to the gabions, you could apply any number of finishes to it. Carpet will rot out, eventually, but it might be worth a try, if you don't mind the possibility of rebuilding after five or ten years. Perhaps if you soaked it well with a clay slip, then allowed it to get almost dry before installing it in the gabion? If that worked, it might act as a geotextile, by itself, and any clay-based facing would more easily adhere to it.

If you use a moving form during compaction, you could get a lot more vigorous (pneumatic ram) and perhaps forego use of geotextile. You would end up with a kind of reinforced tamped earth. It may be sufficient to attach the form to the interior cross panels. If your fill had the consistency of road base it would compact well.