The Magnificent Earthbag Semi Dome of Istanbul

Istanbul is famous for its spectacular domes, many of them commissioned by a well-known Sultan called Suleiman (The Magnificent)*, and realised by his favourite architect Mimar Sinan. None of them were earthbag of course. Until now.
 
Get ready folks, this is probably one of the most technically interesting earthbag structures I’ve seen, with some pioneering design features such as an oculus skylight and a slipstraw insulation envelope. Woohoo! Yes it’s ambitious, even so there’s a lot for everyone to learn from this project.
 
But first let me introduce you to Xavier Allard, the quiet French/Belgian chap with plenty of attention to detail who managed this project. Luckily for us he documented it extremely well too. But who is he? And why is he in Turkey?
 
“I discovered Turkey while traveling and decided to stay”, says Xavier. He’s not giving much away here eh? So I shall interpret this as meaning he rather liked the place, possibly because the food is fab, and the people are friendly? Anyway ten years on he’s still in there.

The Magnificent Semi Dome.

How did Xavier become the Mimar Sinan of natural building?
 “No no, I’m not Sinan, that’s Matthieu Pedergnana**”, explains Xavier. “I’m the builder. It all began when I met Matthieu in Ankara. He’s a French architect who was teaching architecture at Yaşar University...I learned everything on site both from him as a building mentor and on my own, first volunteering on alternative building projects, then organizing workshops myself. Eventually I specialized in woodworking”.
 
The Koluba Team
After a lot of natural building experience, Xavier set up his own natural building organisation called Koluba. The Koluba team have been making plenty of mud beauty over at the Sihirli Tohumlar*** permie farm about 130km from Istanbul. And it warms my heart to see earthen structures once again sprouting on Turkish soil. As you’ll no doubt remember when I built my earthbag house back in 2011, most people thought it was a pile of poop, that it would melt in the rain, and that concrete was God. Sigh.
 
Xavier also has a valuable partner in Koluba, Okan Demirbaş, a structural engineer specialising in plasters and stonework. “Okan is gifted with both a sharp practical mind, the ability to work fast and well, and a deep interest in true craftsmanship, a combination so uncommon that finding new team members is one of our main struggles these days”, says Xavier. Oh and I hear you!
 
So as you can see, we have a very well qualified and experienced team here. Good job too! This build is not for the faint of heart.

Xavier in action.

The Magnificent Earthbag Semi Dome
This stunning structure is 80m2, and it’s unusual because it’s an earthbag semi dome built within a wood/slipstraw structure. It has a reciprocal green roof, and comprises three rooms, two storage bays and a terrace. If you’re a beginner to earthbag, don’t try anything as ambitious or large as this. Koluba had a big team and a lot of expertise on their side.

The slipstraw envelope.

The Foundations (A New Method)
Koluba did something unconventional with the foundations. Instead of the traditional rubble trench, they just used tamped gravel bags laid below grade as a foundation. “We did this a lot on small buildings”, said Xavier, “But this time it had to carry a lot of weight (the roof is 45tons+), and it managed successfully”.
 
This is very interesting news, and it makes sense, because the gravel bags act like a rubble trench anyway, and if they’re laid below grade, they should serve as footings just as well.
 
Post and Beam Structure
Next the team attached twenty 10 X 20cm posts onto the earthbags to carry the roof. How did they do that? The posts have anchors, or feet, on the bottom to increase the contact size, and then they were locked in by another layer of bags laid over the top.
 
The large roof beams that create the roof mandala rest on the posts, and they meet at the centre of the building to form a heptagon over the oculus of the dome. This is the awesome skylight, and it’s beautifully reminiscent to me of the Blue Mosque roof.

To see all this more clearly, watch the timelapse video.

The oculus.

The Slipstraw Insulating Envelope
For me this is one of the most brilliant parts of this building. We always hear how you can’t build earthbag in cold climates. But if you are in a cooler climate, and want to do earthbag, here’s a fantastic way to insulate your structure.
 
First, a series of wall panels were installed between the posts. Then they were filled with 20cm of slipstraw (straw with a small amount of liquid clay, compressed into temporary frameworks). Finally, the earthbag semi dome was built in the centre of that structure. Neat huh?

The plan. Designed by Matthieu Pedergnana, built by Koluba.

The Semi Dome
“The earthbag semi dome in the centre is 4m in diameter, 3m in height. It has 5 openings and is quite flat so we had to add buttresses in the rooms”, explains Xavier. Which brings up a point I’m eager to highlight. Plans always have to shift if you’re a pioneer builder, and you may have to add things you didn’t want to initially. But I tell you what, they always end up being some mighty useful or beautiful feature at some point, as you’ll see at the end.
 
The Roof
The roof beams are connected with about a hundred 10 x 20cm purlins. Then about 20cm depth of hemp chips were poured around them. After that wooden roofing boards were laid, then an EPDM waterproof membrane, and finally 25cm of soil for the living roof.
 
For more details you can see exactly how they did all that in this short but informative video: https://www.youtube.com/watch?v=AlgFqNyno6w

The attention to detail is impressive.

The Interior
There is a kitchen and a bathroom, and the dome serves as a living room.
 
The floors in the three rooms were insulated with hemp chips poured under a wooden floor. Everywhere else, the floor slabs were made with a mix of lime and LECAT (expanded clay) and those slabs were topped with stones.
 
The walls were rough plastered with an earth/sand/straw mix, then the interior walls were finished with clay plasters. The exterior was finished with a lime plaster. The bathroom is tadelakt. And all the furniture and trimming is handmade (beds, stairs, benches, shelves etc).

A pretty amazing place to sit.

A spotless interior.

​Challenges
I always like to mention challenges in building, because there is a naive idea floating around the minds of those who haven’t actually built anything, that if you just plan and research and think about it enough, you’ll avoid all difficulty. You don’t get natural builders and architects more qualified and better-prepped than the ones mentioned here. And yet when I asked Xavier about challenges, he was very transparent and offered a long list. For me, this is the ultimate test of confidence. If you have to pretend nothing ever goes wrong, you’re probably not a pro.
 
All the challenges Xavier mentioned were so familiar to me. And they’ll be familiar to everyone who builds. Plan changes, plaster, roofing, and volunteers, always guaranteed to make you sweat. Notice how Xavier deals with challenges, (namely flexibility, determination, and a good old prayer every now and again:))
 
1. Roofing stress. “The roof was very complicated with difficult angles and large parts to handle. There was very little space for error”, says Xavier, who had to organise the placement of beams weighing up to 300kg onto the roof. Yes it was stressful. And yes it’s a good job he’s a woodworking expert.
 
2. Dome moving outwards. “Another critical moment was when we noticed that the dome was moving outwards due to it having too many openings. We took the difficult decision to add several buttresses sticking out in the middle of the rooms, reducing their surface, but later these buttresses became nice features of the rooms giving support to the stairs or shelving”, explains Xavier.
 
3. Plaster troubles. I always say plaster is one of the trickiest parts of a build. It looks deceptively easy. It isn’t. “Exterior plasters were (and will be) a struggle. The building is very exposed to strong northern winter winds and lime plasters got badly damaged in some places. We repaired and reinforced this year but there might be much future maintenance needed at those sensitive points”.
 
4. Finishing that never finishes. “This actually took most of those 11 months”, laments Xavier. “Hundreds of details to care for, starting with the rough plaster phase”.
 
Yup brace yourselves. The structure is the easy part. The finishing phase is misnamed and should be called the punishing phase instead. It will demand every ounce of determination from you.

A perfect finish (eventually).

​5. What, no shower? “Another problem was the shower”, says Xavier. “That little room had been designed to house a toilet only, but the owner asked for a shower on the way”. He he he. Oh the joys of doing commission work. He continues, “Walls were there, a big wooden post in the middle of the only possible spot for that shower. So we embedded burlap mesh in the lime, waterproofed as much as we could, applied tadelakt over and prayed to whichever god deals with plaster cracks. A year later the shower plasters are intact”.
 
I love that they prayed to the plaster crack gods. And I love that it worked:))
 
6. Volunteers. “I can also add that having to work with volunteers is sometimes a major challenge in this type of project. Some people will be capable, learn quickly and turn out to be productive, others will be a burden whose work you’ll need to check constantly, perhaps even redo and waste even more time. It is a lottery”.
 
Oh preaching to the choir with that one Xavier! But despite the mixed experiences, Koluba are still bravely taking on new volunteers.
 
Want to Volunteer with Koluba?
Koluba are accepting volunteers with some woodworking experience this year. It will be a different location, in the beautiful Kazdağlar mountains near Çanakkale. For more details contact Xavier/Koluba at the address below.

Volunteering at Koluba.

​Contact Koluba (and see a stack more stunning photos) at:
Instagram/Facebook @kolubakolektifi
Website: www.koluba.org
 
Other related links:
**Architect: Matthieu Pedergnana @dogalmimar
***Location: @sihirlitohumlar
 
What is slipstraw? https://strawclaywood.com/natural-building-techniques/straw-clay-or-slipstraw/
 
* And if you want to catch up on a glittery piece of Turkish history (albeit glammed up to the hilt), then grab some popcorn and indulge in the historical romp that is Magnificent Century, one of Turkey’s best-selling media exports.
https://www.youtube.com/watch?v=N2ZlLE4z__4

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