Some considerations about domed and vaulted roofs

Each space in the house has an independent roof. So it is starting to look like if several domes, vaults, or combination of both, are placed against each other (picture at the bottom). Until now there is a reciprocal roof over the living room and 3 domed or vaulted roofs (or a mix of both).  One vault is over the entrance corridor and two domes cover each a room. The one I am making now is the dome over my room, which is quite irregular in form so as a consequence the dome is also irregular, you can see some info about it in the previous post here: Domed roof over an irregular shape.  The roof over the living room is a 12 beam wooden reciprocal roof, but I will probably replace it by a big dome.The reason is because I did it before I learned about domed roofs and how beautiful they were. Here are some pictures, from a facebook photo album, about the reciprocal roof: Reciprocal roof. The pictures document a bit what I was doing.

The domes have no supporting poles, they lie over thick (60 cm wide) walls. All the domes are also lying against each other in several sides (the internal walls of the house), that eliminates the horizontal forces there. In any case the walls are thick and rounded (the house is basically an hexagon), and the thickness of the domes so thin in comparison to the supporting walls, that there is no issue with horizontal forces pushing the walls. The thickness of the domed or vaulted roofs  is 10 cm corresponding by the width of the brick, plus more or less 3 cm stucco over that, so a total of 13 cm (which I just noticed that it is not a lucky number!). For the living room, the biggest space, the thickness for the bricks of the dome I plan to make, replacing the reciprocal roof, will probably be 15 to 20 cm in the lower part of the roof and 10cm in the higher part. But that could change because maybe I will stabilize the bricks with lime or fire them to make them harder without needing to make them thicker. I add to that the 3 cm of stucco.

The stucco to make the domes (or vaults or combination of both) water resistant is something similar to Tadelakt, that is lime with vegetable soap, like olive oil soap or coconut soap or soya based soap etc…. rubbed hard with a smooth river stone or steel trowel, except that in the inner part I also add clay. Lime is mostly pure with no clay in the exterior part of the stucco. Lime reacts with the soap and makes it hydrophobic, water resistant, but still breathable. Still a lot to work so I hope it will all workout OK :).

Roofing has been a challenge but very gratifying and where I have learned and enjoyed most. Those flat domes are a pleasure to work with. If you used unfired bricks 20x10x5 cm the domes and vaults should not have more than 8 meters wide, if they are fired bricks it could go up to 10, beyond that I should start using thicker bricks at least in the lower parts of the domes or stabilise them by compression and/or with lime.

Several options…. Seems complicated but less as I gain experience. Testing is important. I started with very small spaces and got each time bigger, to build confidence and experience. At the end it gets simpler and simpler and it is very pleasant to work with. I still consider myself a rookie and have had bad experiences on the way, but then again, those made me want to work harder to get it right, and it seems to be working.

 

Best wishes !

jrv

 

PD: This is an old picture when there were only 2 domes, there is now a 3rd and bigger dome on the back.  They are also without plastering in the picture (not anymore). It gives an idea of how the domes lie besides each other as well as how the final result will be when all the spaces will be covered: 12140083_10153349286778401_2409549385569915495_o

3 thoughts on “Some considerations about domed and vaulted roofs”

  1. great post.

    When you have two arches coming together at right angles do you cut the first brick in the groin? Maybe as you do nubian way and the bricks are not vertical you don’t have to. This was one of the most difficult for me to discover, the groin bricks.

    We have maybe 50 vaults / domes and i learned someting new in your post.

    1. Hi Erick ! You have made a lot of domes ! The horizontal forces that the domes exercise against the walls could be an issue if the wall is too thin or the roof is too heavy. So it is a possibility to have domes against each other to eliminate those forces. In such cases since the forces come on opposite senses they annulate themselves to a great extent, and most that remains are vertical forces well supported by the wall. The arches themselves are supported by the thick wall (one dome on the left side of the wall and the other on the right), and there yes I modify a bit the place where the brick and the side of the wall fit together so that the contact area is maximized and well anchored.

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