After several small span Catalan roofs we decided to roof this room using our new skills. This method is referred to by many names: Catalan, timbrel, cohesive tile. I will use Catalan.
First we built end walls to draw the catenary shape templates, run strings to control the shape, and "glue" the tiles.
I bought handmade floor tiles for the first course for aesthetic reasons.
Butter two sides of a tile with gypsum plaster.
And then move on to the next one. It is a bit tricky as the first one has to be "set" so better to build in two places or use gypsum that is almost set.
Building on each side .
Conduit pipe for ceiling light.
From above 3/4 done with first course of tiles. Sometimes extra gypsum plaster applied to help hold until an arch is completed. gypsum gives no strength to the vault, it is just to hold until an arch is finished.
About to close the first layer. We were excited about how good it looks.
After finishing the first course. We had disagreement on whether to do the other 2 laminate layers as we went along or finish one course at a time.
It did bring and issue .
Before I talk about the hole. This shows the 2nd and third courses with different bonds, first at 45* then at right angle to original bond. After 24 hours you can stand on the 3 layers. Mortar is cement - lime - sand 1-1-6.
Mason Dickson preferred to finish first course then sit on the end wall and lay 50cm of other courses, next day sit on the first 50 cm and lay another 50cm. Worked okay until someone put something heavy on current days work and it collapsed!
As it dried out efflorescence occurred on the beautiful tiles but i figured it would dry and fall off like our bricks. It is a year and still ugly like this. I just tried washing it off and that looks like it will work.