Adobe Test Dome: 4' Diameter

Thought I'd see what a little adobe can do.  Just finished testing this dome today.

...take a look here if you want the whole thing:

http://twobirdstone.blogspot.com/

I learned a few things and I'll do my best to answer if I've got one 

twobirdstone wrote:
Thought I'd see what a little adobe can do.  Just finished testing this dome today.

...take a look here if you want the whole thing:

http://twobirdstone.blogspot.com/

I learned a few things and I'll do my best to answer if I've got one 

What happens if you build a fire for a while before the water test?

Len wrote:
What happens if you build a fire for a while before the water test?

I take it you've read Nader Khalili's Ceramic Houses and Earth Architecture !

If you haven't, Nader fires adobe structures for 17 to 25 hours to turn them into ceramic objects impervious to rain... 

...here's me weighing two things:  ......many gallons of kerosene/a tall tower/welding a specialized kerosene torch/a very long fuel hose/temporarily sealing the building

versus

three 80lb bags of cement mixed with adobe

....hmmmmm..... for me, the bags of cement win out -but just barely.

if anyone knows of a mixture I can create from desert land materials to stabilze the adobe and mortar, I'm listening (no, I'm not interested in commercial products like asphalt, commercial lime etc... -but, anything I can make from juniper, ashes, etc WHICH YOU HAVE ACTUALLY TRIED AND SUCCESSFULLY TEST -I'm very interested )

small domes like this are extremely stable, but if you made a 20 ft one, it would fall down.

You could make a 4ft dome out of almost anything (even paper, literally) and it would hold up to impressive weight tests.

Around here, folks use lime and prickly pear juice to seal adobe....

kool test

spystyle wrote:
kool test

Thanks for taking the time to comment here Velacreations  -I'm a fan of your website: it has some great info on it.

...interesting you state that a 20' diameter dome would fall down.  What shape of dome are you assuming would fall down? 

Are you familiar with Auroville Earth Institute's ( in India) dome building theories and practices?  Are you aware of the "middle one third" theory of thrust at the base of the wall?  Have you tried them?

Please elaborate on your statement that a 20' diameter dome would fall down with in the context of shape and horizontal thrust.  Without this kinda of discussion, your statement, by itself, "falls down" unsupported of any context or explanation.  Aurovlile's site has standing buildings of much larger diameters which disprove your unqualified statement  -since your work is good, I await a more qualified statement from you.

What interests me more than your "fall down" statement was your mention of prickly pear slime: 

-could you spell out how this slime is used? 
-is it mixed with the adobe bricks and mortar?
-or is adobe mixed with it and applied like a stucco?

again, I appreciate the work you've done in the past and I eagerly await your reply!

Ooops!  quoted the wrong person in my first reply  -I repeat this reply in order to trigger a response from Velacreations , should they be so gracious to do so.

velacreations wrote:
small domes like this are extremely stable, but if you made a 20 ft one, it would fall down.

You could make a 4ft dome out of almost anything (even paper, literally) and it would hold up to impressive weight tests.

Around here, folks use lime and prickly pear juice to seal adobe....

Thanks for taking the time to comment here Velacreations  -I'm a fan of your website: it has some great info on it.

...interesting you state that a 20' diameter dome would fall down.  What shape of dome are you assuming would fall down?

Are you familiar with Auroville Earth Institute's ( in India) dome building theories and practices?  Are you aware of the "middle one third" theory of thrust at the base of the wall?  Have you tried them?

Please elaborate on your statement that a 20' diameter dome would fall down with in the context of shape and horizontal thrust.  Without this kinda of discussion, your statement, by itself, "falls down" unsupported of any context or explanation.  Aurovlile's site has standing buildings of much larger diameters which disprove your unqualified statement  -since your work is good, I await a more qualified statement from you.

What interests me more than your "fall down" statement was your mention of prickly pear slime:

-could you spell out how this slime is used?
-is it mixed with the adobe bricks and mortar?
-or is adobe mixed with it and applied like a stucco?

again, I appreciate the work you've done in the past and I eagerly await your reply!

velacreations wrote:
small domes like this are extremely stable, but if you made a 20 ft one, it would fall down....

really?  these pics are taken directly from Auroville Earth Institute's website:

{one is a dome and the other is a vault}

http://www.earth-auroville.com/?nav=menu&pg=vault&id1=2&lang_code=en

one is 10.35 meters and the other is 22.16 meters

that translates into:  33.96 feet for the valut and 72.70 feet for the dome

please qualify what you meant when you said a dome of 20' would fall down.

Twobirds: I appreciate your sharing of the dome and test, but some of your other posts are more aggressive than Paul likes

please read the be nice and name preference threads below

https://permies.com/bb/index.php?topic=2296.0
https://permies.com/bb/index.php?topic=1621.0

oh, I'm not saying that it isn't possibly to build a 20 ft diameter earthen dome, I know it is completely possible.

But the style that you built, it wouldn't go past 8 feet diameter, probably.

Those Auroville domes are awesome, and I'm a big fans of theirs, but there are a couple of things that differ from your design.  They are using compressed earth blocks, which makes a huge difference, as the earth is in compression on a dome, so it is like it is "pre-stressed" with a compressed block.  They are also using specific techniques to make it work, including making the base extremely thick to compensate for the diameter.  Their bricks are also different shapes, making it easier to lay, thicker ones at the bottom, and gradually decreasing towards the top.

My statement wasn't meant as an attack on you, your work, or earthen construction.  I was merely illustrating the fact than small domes are easy to make, even without much thought. You can make small domes out of just about anything, including paper, and they will hold several people, but if you take that same technique and try to scale it, it won't work.  Larger domes have specific considerations. Hassan Fathy recommends than domes not exceed 3-4 meters in diameter if the bricks are not compressed.

So, don't try to build a large dome using the same techniques that you used to make your 4' dome.  Use 20' dome techniques for a 20' dome....

As for the prickly pear/lime "putty":
Folks take prickly pear pads, chop them up, then soak them in some water overnight.  Most of the juice from the pads flows out into the water.  The next day, they drain the water/juice out, mix it with lime and make a putty than they apply in several thin coats over adobe.  You apply a coat kinda like a thick paint, then let it dry, then apply another coat.  This makes a very good waterproofing agent, even on roofs.  Most folks do this every 5 years or so, adding layers of this paint.  I've had the chance to look at several adobe buildings than are 300 years old or more in the area, and the paint layer has grown to be 1/2" or more thick, just with many, many applications over the centuries.

one more thing that I forgot to mention, Auroville often uses stabilized compressed earth blocks, blocks that have some lime or cement in them.  Although it s not much, it does add to the compressive strength of the block vs plain adobe.

Good luck with your work!

velacreations wrote:
oh, I'm not saying that it isn't possibly to build a 20 ft diameter earthen dome, I know it is completely possible.

But the style that you built, it wouldn't go past 8 feet diameter, probably.
.....

Velacreations  -thanks for your thoughtful qualification and the information regarding the prickly pear putty/paint!

From your quality work on your website, I knew you wouldn't disappoint me with your reply.

...and thank you for warning me and others about the complexity of a large dome versus a smaller dome  -I failed to do so both on my blog and on this forum.

I intend to use a completely different style of adobe brick than the one I used for the small test dome.  -I've never built ANY domes at all before I built the one I posted. 

My goal with this test was to understand and gain the mechanical techniques of using the compass method Auroville has listed in their downloadable pdfs.   ...and to see: how a dome falls down under water erosion if not protected/stabilized, how quickly it does so, and if my technique was good enough to support weight on top of the dome.

...you're right, if an uniformed person didn't read Auroville's information carefully, have some concept of vertical, circular, and horizontal thrust, and then tried to build a large dome, someone could get hurt!

...so qualifications were needed from both of us, I'm glad you did too (just hope this doesn't get me banned from permies.com for aggressively asking for your qualification to the fall down statement).

Thanks again on your prickly pear info  -I'll be doing test using it along with some compression test and tensile tests on the type of brick I intend to use on a larger dome.

Just for the record, I didn't think you were aggressive or attacking in any way.  I know I have been so in the past, and I'm not banned (yet), so I think you're ok.

In addition to Auroville, do read up on Hassan Fathy and Persian dome construction, and also nubian vaults.  There are ways of doing it with simple adobe bricks (not more than 4 meters diameter), but you have to be careful with your techniques.

I would also consider compressed earth vs adobe.  I have built using both, and I'll never do adobe again.  Compressed earth saves a ton of time, labor, and water.  Plus, it is a lot stronger in compression (think pre-stressed).

Also, if you are really into domes, check out earthbags.  They are considerably faster and don't depend so much on clay/sand ratios.  I've seen several 16ft domes built with them, even by novices.

That brings up another point about domes.  Cone-shaped domes (like the earthbag beehive shape) are actually more stable than hemispherical domes.  The reason is they are closer to a catenary shape (everything in pure compression).  The advantage with this design is that your ceiling is much higher, so you can put in a loft, and increase usable space.  Persian domes take advantage of this, and are easier to build with basic adobe bricks.

Attached are images from Gernot Minke's Build with Earth showing Persian and Nubian dome techniques.

by the way, when I say compressed earth, I am meaning compressed earth blocks.  I have never used rammed earth and consider it less than ideal (except in the case of earthbags)

velacreations wrote:
...
In addition to Auroville, do read up on Hassan Fathy and Persian dome construction, and also nubian vaults.
...
Compressed earth saves a ton of time, labor, and water.  Plus, it is a lot stronger in compression (think pre-stressed).
....
Also, if you are really into domes, check out earthbags.  They are considerably faster and don't depend so much on clay/sand ratios. 
....

The reason is they are closer to a catenary shape (everything in pure compression).  ...Persian domes take advantage of this, and are easier to build with basic adobe bricks.

Attached are images from Gernot Minke's Build with Earth showing Persian and Nubian dome techniques.

I'll definitely check out  Hassan Fathy and Persian dome construction (one of us is trying the Nubian Vault method currently).

I'm a little crazy in that I like to ask my self, "if someone stole my tools and stripped me bare naked, could I build it" and then go upwards (technology-wise) from there. Obviously, I still want my shovel, a level, 5 gallon buckets, and a wheelbarrow.

The earth bag method I'm slightly prejudiced against because I don't like encouraging the manufacture of plastics and the bags cost money (now, if you know a way a poor person could manufacture bags...maybe I'd weight this against my prejudice).

I liked compress earth bricks but the price of the machine, for the poorest of us, is pretty steep, and would get stolen once people realised the value of it.

Does the use of a compressed earth machine really save time and labor?  That's not a rhetorical question  -I watched OpenSource Farm (now OpenSource Ecology) run a test on their first CEB machine... it took a lot of people to feed the machine and their conclusion, or should I say, Marcin's conclusion, was that it was no faster than building a cord wood wall.  Of course, Marcin is geared towards fast machine production. (Now OpenSource Ecology says they have an automated CEB press, fed by a tractor, which meets their high production goal).

I'm not sure how you could use words to explain how using a CEB press saves time and labor (other than the drying time which CEB has none if I remember correctly). But I'd listen if you're so inclined.

The catenary shape is the final shape I'm actually looking for, because, as you mentioned, all of it's members are in compression in such a way that the horizontal thrust is in the middle third of the base of the wall.  -I just haven't figured an easy way to do it (easy as using the compass for the hemispheric domes).

Awesome images, by the way, from Gernot Minke's Build with Earth!

twobirdstone wrote:

The catenary shape is the final shape I'm actually looking for, because, as you mentioned, all of it's members are in compression in such a way that the horizontal thrust is in the middle third of the base of the wall.   -I just haven't figured an easy way to do it (easy as using the compass for the hemispheric domes).

Awesome images, by the way, from Gernot Minke's Build with Earth!

According to this article:

http://www.asl.uni-kassel.de/%7Efeb/wissenswertes/manual_engl.pdf

The catenory curve is not the best curve either. He gets into domes at about page 42 or so, but the whole article is about earthquake proofing and deals with adobe as a building material as well. In fact the whole thing is about earthquake resistant earth homes.

I found this on the MHA website. I guess they build brick ovens as well and thought this info might be useful. There are a few more links on there to dome construction (bigger than an oven), but I can't find them just now...

The earth bag method I'm slightly prejudiced against because I don't like encouraging the manufacture of plastics and the bags cost money (now, if you know a way a poor person could manufacture bags...maybe I'd weight this against my prejudice).

Used bags usually go to the landfill, but would be fine for construction.  Creating a use is a good way to avoid the environmental costs of these bags sitting in a landfill.

People report about 10-15 square feet of wall per person per hour with earthbags.  That is a considerable time savings, which also not needing water or mixing materials.  That's like 60-90 sf a day per person.  You won't get that with adobe or CEBs.  A little waste plastic is a decent tradeoff for significant time and labor savings.

Does the use of a compressed earth machine really save time and labor?  ....
I'm not sure how you could use words to explain how using a CEB press saves time and labor (other than the drying time which CEB has none if I remember correctly). But I'd listen if you're so inclined.

Yes, it does save considerable time and labor.  It took me months to build a 16ft by 25ft room with adobe blocks, and a matter of days to build a 30ft by 12ft room with CEBs.  The uniformity of the brick, the weight, the reduced or eliminated mixing time, the reduced curing time (28 days for adobe vs a week for CEB) all contribute to the speed.  CEBs also use a fraction of the water than adobe requires.  If you make interlocking bricks, you can even stack them without mortar, saving more time and money. 

With adobe, you have to mix your material, and that takes a long time. I was never able to make 500 adobe bricks a day, but people often report such rates with manual CEB machines.  Mixing adobe for a test is easy, but for a real house, it is a lot of hard work, and then you have to wait a month before you can use the bricks. 

That's not a rhetorical question  -I watched OpenSource Farm (now OpenSource Ecology) run a test on their first CEB machine... it took a lot of people to feed the machine and their conclusion, or should I say, Marcin's conclusion, was that it was no faster than building a cord wood wall.  Of course, Marcin is geared towards fast machine production. (Now OpenSource Ecology says they have an automated CEB press, fed by a tractor, which meets their high production goal).

While I am a fan of OSE, I do not think they take the most appropriate routes all the time.  No one over there is an expert at construction, and they have very little experience with building materials. I haven't even seen a competent brick layer (just look at the walls in the photos).  They also laid their CEBs across the wall to increase the thickness, which requires a lot more bricks and increases the labor.  Their mortar joints were very thick, like 3/4", which also increases time and cost.

Manual CEB machines can be efficiently run by 2-3 people and produce 400-600 bricks a day.

for catenary jigs, take a look at some of the ones used by earthbag folks.  They basically have 2 points of reference instead of a center point.

Alternatively, you can make a guide with rebar or something stiff, and rotated it around a central point.

The Persian/Afgan domes in Minke's book follow end arches that are catenary.  The follow that shape and form a larger catenary dome.

Corbeled domes are a bit easier (that's actually what an earthbag dome is), and although not true catenary, you can get pretty close with this method.

Great thread.  I've thought about domes, but figure that's too fancy for my needs.

To velacreations, have you any experience using a wet-pour method of adobe construction?

I've come across a website/book from a guy who has developed such a system, basically using a wet-ish adobe mix and pouring into a keyed-two-block wooden form preset into place.  Once the new pour is set, the form is removed, placed next to the new blocks, and another pour is made.

http://www.cheapasscurmudgeon.com/

He used to have a short ebook describing the process.  I see he's moved up to full color printed books, and, unfortunately, the website provides no details at all, but I hope you'll get the idea.

I'm wanting to use this method here in the Colorado plains, for a smallish four-sided house, so any comments are welcome.  Thanks.

And, to the OP, good luck with that dome.

yeah, he has a system similar to what we developed to make adobe faster.  I'm not going to say he stole our idea, cause I think he came up with it independently, but he didn't "invent" the process.

http://www.velacreations.com/adobe.html

It is super simple to do, just make some forms and place the wet adobe right on the wall.  You can pull the form off in like 5-10 minutes.  We made several forms, made a big mix, and by the time we were filling the last form, the first form could come off and move to the front of the line.  We called it "caterpilling"

Ah, now you mention it, I seem to recall looking at your site awhile back, which jogged my memory of this other system.

I doubt he stole the idea from anyone.  It seems like a natural progression from individual solid blocks to a poured wall similar to concrete.  I've never worked with any of it, though.

Would you recommend "poured adobe" for a smallish rectangular house?  How does it hold to stresses, bearing loads, etc., if you have any insights.  Thanks again.

yeah, poured adobe works fine.  It is labor intensive, and I would never do it again (I prefer earthbags), but it works, and it's cheap.

As far as stresses and loads, it works just as well as regular adobe.  I would make your walls at least 9" thick, and pay attention to design and window/door placement.  We used a stone foundation for our house, but I'm sure any standard foundation would work.

Poured adobe is actually similar to cob, just using a form to make it go faster.  It will take a while to dry out.  We built the roof structure first, and the walls underneath, so that we could work in the shade.

Wow.  You just changed by plans for the better in several ways.  Simple stuff, too, which I like.

I gather you favor earthbags.     I like the idea, but I really don't want to spend money on the materials.  When/if this project happens, I'll have time and labor (mine) at my disposal for defined lengths.  Money, probably not so much.

If I can pour/erect a fraction of the wall system each time, and can simply wet down the old and pour the new and keep on muddin' on, then all the better.  It can wait on me.

Building the roof first had only just begun to occur to me.  I'd been curious about ramadas a few weeks ago, did some googling, and have just perused the manual you linked to earlier, noted the detached roofing system, and now you mention doing it, too.

Great!  I had been concerned about the walls carrying the roof load, the building of the roof itself, etc., but now I could essentially build a pole barn over the building site and just close in the space I want, and use adobe for the top of the box, so to say, as well.  Yes?

Did you later join the roof and house, or not? 

Sorry to hijack the thread.  It'll get split if need be, no doubt.

Thanks again!

yes, we made a pole barn first, and then the adobe absorbed (for lack of a better word) the poles as we built the walls. You could make the poles out of earth or concrete, and that would make it cheaper and stronger.  Check out fabric forms:
http://www.flickr.com/photos/velacreations/sets/72157621856458153/
http://www.flickr.com/photos/velacreations/sets/72157614563674020/
http://velacreations.blogspot.com/2009/02/fabric-forming-posts.html

I'm not a big fan of metal roofing, though.  I prefer concrete and/or earthen domes/vaults. 

You might consider latex concrete for the roof, it is lightweight and as fast to put up as metal. Check out this for a bit of info: http://velacreations.blogspot.com/search/label/latex%20concrete

Do you have a decent deposit of adobe near the house?  Do yourself a favor, spend a bit of money on lime.  Add 5% lime to your adobe blocks.  It really makes a difference, and it is a minimal cost.

Yes, you are right, I do favor earthbags.  I have been building for over a decade, and I've tried a lot of different things. I am continuously looking for easier, cheaper, better.

This is how I would rate earthen methods:
rock/stone > cob > adobe > t-brick adobe > CEBs > earthbag

But in a few years, I'll probably discover something faster, cheaper, better than earthbags....

Interesting stuff there.  Thanks.

I'm not sure yet of my soil conditions on site, except for generalities of the area.  I'm confident there will be enough dirt, clay, sand, chaff, etc. on 40 acres of High Plains to build at least one small cabin.  An assumption, to be sure, but adobe building is long known and used in this area.

And, if the dirt won't work, I'll just build the thing as a panelized system using standard dimensional lumber.  One way or another, I plan to live there.

I was leaning toward a metal roof, for the relative simplicity of buying the materials and fasteners locally, and it being lightweight.  No fancy roof hips or valleys or other fluff.

I don't intend to build more than a few small structures, of less than 200 sqft, perhaps a small house (650 sqft) much later (if I must).  It's only me, so I don't and won't need much.

Thanks again, and good luck with your projects.

The results are impressive.
What do you propose would be the best way to water proof it?

I have thought these proof of concept designs would be good for animal enclosures.

Campy in Nashville, Tennessee, USA wrote:
The results are impressive.
What do you propose would be the best way to water proof it?
I have thought these proof of concept designs would be good for animal enclosures.

uh, well, I asked that question and velacreations responded above with some good methods...  I'd rehash them but velacreations did a great job of answering -if you scroll up and read his post, you'll find other interesting info about domes too.