Building the SUDU

SUDU completed!
June 4, 2011, 4:45 pm
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7 Comments so far
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I’ve been checking up on the SUDU project on the site and I have to say, I really love the building. I have heard that there have been two commissions to construct SUDUs. Can you please verify and expand on that? Also, how long does it take to build one SUDU and is it competetive compared to the speed of the condominium construction in Addis? Many thanks and keep up the great work!

Comment by mali

wow its really nice project and i appreciate your effort in making such affordable houses in ethiopia

Comment by biniam wondimu

Realy amazing, what u have done . So i have a question how much did it cost totally? and do u do any other houses or u just made only the sample one????

Comment by Dave

I have read the entire blog several times and think this is very exciting tech. I was wondering if there was an update on the livability of the structure now that it’s been in place for a while- would the people who live there change anything about it?

Comment by Seannon

Thanks, Seannon. The building is being used currently as an office space for the chair of appropriate building technology at the Ethiopian Institute of Architecture, Building Construction and City Development. I can’t speak for the chair-holder regarding livability – as an office, I think it works very well, but it has not been tested “in the field” with residential occupancy. For this, please reference the SRDU (Sustainable Rural Dwelling Unit) project, whose longer-term research is attempting precisely to address this question.

Otherwise, it is important to note that this particular design demands measurable improvements to respond more appropriately to the climate in Ethiopia.

Comment by limacon24

This is great stuff. Thank you for posting it. It’s fairly complete excepting a few details. The tiles used are??? The links say loam but if you look at the definition of loam it is rather foggy. Maybe a jar of water and “loam” shaken up and explaining the constitute members. Maybe a simple test to load the tile with so many gallons of water to show what you have to have strength wise before breaking’ Uhh…how do you make a loam brick/tile?
How big are the tiles? Were they made with a compressed earth “ram” machine? As I understand it they had no cement in them but I’m not sure in some places seems I read they used portland cement.

Looking at the pictures it seems you use three layers of alternating pattern tile but you don’t say so directly. Is this correct? The tiles are connected with plaster but after the first tile layer is done do they use portland cement to cover those or is it more plaster? On the second course of tile do they just lay a layer of cement or plaster then embed the tile? Do they use on of those square scraper trials that cuts square grooves in the cement or plaster to get the thickness the same? Same as is used in a normal ceramic tile laying. Exactly what is the fill in the second story floor? Would anything do or do you need “loam”, whatever that is.

Be nice if you had the same level of detail on the making of the roof.

Have you thought about using rope for the tensioning in the lower floor and the upper roof? They may not have a steel factory in the bush but they sure have some kind of grass or plant fiber for rope. Easy to make and cost zero.

You could make the rope as strong as needed then triple by using three separate ropes. That way you could could pull out old rope and pull in new without compromising the building. People could easily test the tension on the rope by plucking it and hearing it’s tone. If it gets too low replace or tighten the rope. The rope could be placed on top of the vault. Covered with a little grass, cardboard or other filler and plastered over to make a channel. That way it would be easy to replace the rope every couple of years or so. The rope should last a long time as it would be dry and inside. If you really wanted to be anal about the rope you could paint it with pine tar like the ship builders used to do with their rope and it would probably last the length of the building.

My apologies for seeming to be negative as I’m not. You’ve done a great deal of work and tied it together in a fabulous way. Thanks for the work.

Comment by Sam

Dear Sam,
Thanks for your for your comments. This blog was done about 5 years ago, and was not meant as a comprehensive technical overview of the project. For many of your questions, it would be be useful for you get a copy of the recently published book volumes: “SUDU Research” and ” SUDU Manual”, edited by Hebel et al., published by Ruby Press:

For specifications on earth as a building material and in particular for Compressed Stabilized Earth Block (CSEB), it is strongly advised that you refer to manuals produced by earth building specialists (e.g. Auroville Earth Institute, CRAterre, etc.). The CSEB produced for the first phase of this project was very poorly executed, and I would not recommend the SUDU manual publication above for such technical matters (e.g. in one place, it is mentioned to allow the CSEB to dry after production; which is a terrible mistake, as all cement stabilized materials must be cured with water for a period of 28 days to come to full strength).

The CSEB intended for the vault described in the blog were compressed stabilized earth block (8% cement stabization) produced with a hydraulic CSEB press.
However, these blocks did not have an appropriate soil grain size distribution, were not produced well, not properly cured and not produced in time. Consequently, the first layer of tiles are of trachyte stone (not compressed earth), and the second layer are of low quality terrazo tiles (which was also a replacement for the CSEB which were not properly produced).

The “foggy definition of loam” is correctly observed. Again, you can check the SUDU manual for more specific information, but the documented consituent components of the soil are not reliable for this project. Please refer to other technical resources for specifications on CSEB. There is a lot of published literature/ practical manuals on this; one is the “Production and Use of Compressed Stabilised Earth Blocks” by the Auroville Earth Institute:
Whichever technical manual you use, it is advisable to have proper training in CSEB production (like that provided at the Auroville Earth Institute) and to consult with the most appropriate local building codes for CSEB/CEB (if existing).

Yes, correct, three layers of alternating pattern tile; first layer set with specialized rapid setting gypsum mortar, subsequent layers and all bedding laid with portland cement mortar. Basic best-practice in masonry requires that the bedding layer is not pre-compressed before laying block or tile. Scrapers can be used but it is not needed if the masons have any basic skill. If the gypsum course is mortared roughly on the extrados (as is commonly the case), scrapers would not work very well.

Fill of second story floor: Refer to document above. I was never sent reliable specifications on this fill material, although it was some variation of a lightweight volcanic material in a stabilized lime matrix). Note that the proper density of the fill material (according to the actual mix ratios) should always be incorporated into engineering calculations for vaults.

Tension ties of hand-spun rope are not reliable for engineered structures like this (although there is beautiful work on traditional hand-spun rope tension bridges). Even steel in resource-constrained contexts can be insufficient if not properly sized and detailed (as in the case of the SUDU). There are however plenty of engineered alternatives for tension ties in development now (e.g. engineered bamboo, basalt, fiberglass reinforcement).

Comment by limacon24

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