@Kira Hipull ++: While working on rectangular cobbins with Miguel, he told me that rectangular are often MUCH faster and easier to build than "round" cobbins, which makes sense with all the added steps we see, especially for roofing, when doing 8, 10, or 12-side cobbins that look round. Also, building into earth can be easy if you have a slope, digging out only part of what you need, and using what you dig out to fill in around when making-filling in a living roof that blends into the surrounding land. He used various kinds of quite thick pond liner and other similar materials that I can't name by memory, but are in more of his recent (early summer) course videos of the many cobbins he made in spring-summer 2026. Hope that helps add more info. and @Ursa Shapla : I wish I had a good imagining of what you mean, 1. (I don't have time to look up what a zome roof is at the moment), and once that is known, 2. how you seek to add an overhang? plus 3. How that could like like a huge ice cream cone. Did you draw up your plans at all? Have you started so you can share photos??