I have worked in building maintenance and repair. One thing that is extremely hazardous to a concrete building is too much water. I have seen many concrete planters that crack and result in water leaks for lower levels. Standing water in concrete structures is a huge no no. I do not have a lot of experience in engineering on this matter, but whenever I see a solar punk sky scraper with vegetation on its exterior, I think “cool, but maintenance and inspection must be horrible! Repairs must cost a fortune when those roots and moisture degree the concrete.”
What engineering controls does one need to create a durable structure while exposed to constant moisture needed for vegetation, and the vegetation itself? I know there are green sky scrapers with gardens all over. What is the maintenance of those structures? Do they hold up\last as long as bare concrete structures?
Isn’t this one of the big reasons why the Florida apartment complex collapsed?
I started thinking about this yesterday too, after watching the Ask This Old House guys remove moss from a roof, explaining that it will retain water and shorten the life of the shingles. As some houses are prone to moss, you’d think we’d just figure out how to make a bio-roof. That seems like your step one to a veg-roof.