posted 3 hours ago
The biggest complaint I read about domes is that they leak, if not right away, eventually. Thus, I think I would suggest you consider a multi-layer approach. If there was a way to make a top layer with a gap to the lower layer, designed in a way that any water that made it through the top, would be directed towards the edges, that would be brilliant.
Yes, it would be lovely to do a really permie option, but domes are tricky. I think the best option I've read about uses fiberglass screen attached to the frame and then painted with Latexcrete. Started thin to make sure it penetrates well, then multiple layers "painted" on in different directions, possibly adding a second layer of fiberglass fabric or screen, and then more layers.
One of the things about roofs, is that the flatter the roof, the better sealed it has to be to prevent water getting in. The top of the dome is very much like a flat or low slope roof. In my wet climate, low slope roofs are often covered with a heavy rubber roofing material professionally sealed anywhere it joins. In a dome, there will be a *lot* of joins. That said, I am unaware of any permie law which says you can't use rubber on the low-slope parts at the top, and a different material further down once your slopes are steeper. My son was working on a project and wanted a metal roof for rainwater harvesting. They had to change the design so that the roof slope was steeper because metal roofs are sensitive to this problem.
I'm really glad that you're building a knee wall for your dome. Essentially, that is how a yurt is constructed and the difference in the functional space will be noticeable. If I'd seen this earlier, I would have suggested you dig out an area under the deck that will be covered by the dome, and frame it in as a "cool cellar", or at least a storage spot that isn't easily noticeable from outside.
It looks great so far - happy building.