I'm looking at this concept illustration with a bunch of little houses and gardens across the roof of a shopping mall and I'm wondering how deep the homeowners can dig in their gardens before becoming a roof membrane problem. #housing Developer wants to build 500 modular homes on roof of struggling Sask. mall | CBC News https://www.cbc.ca/news/canada/saskatchewan/prince-albert-gateway-mall-500-modular-homes-9.7392495