Bill it's nice,. but to have a supporting vehicle [arch/dome] it needs to be wedging into a non-moveable, or an opposing side.No, it's mortared. It is a corbeled vault though, which is a first.
The Galloway I found is only 10' wide and was lime mortared. It has 3' thick walls and when you add the two walls it deducts 6' from the span.Yes they lable it a corbelled valt but when looking at the walls they are really practically built like two leaning stone walls, especially the exterior. and very steep! When those two leaning 36'' walls [or so called corbelled walls ] meet at the middel of the 10ft.building 1/3 of of eadc 36'' wall is actually plumb over the spring point.Francis, I don't mind the criticism, but it is not warranted this time. Corbeled vaults are actually traditional. One very famous example is the Galloway oratory, an early Irish church that also happens to be dry laid.
My little building does not really compare, but there is almost four tons of stone in the roof. I think it would have collapsed during construction if it was going to.
The stones wouldn't need to be tight to lock without mortar, just have 2 points on each edge touching so it's more than just a pivot. Mortar is better in the short term (the next 70 years or so in his climate)Bill you pitched it then they can't settle forward as it actually locks.
The thin rocks are best being cemented as I'm sure the edges aren't all square to lock against each other if they were butted tight.