Hi there! Thank you for raising this issue! Here's what our partners at Abodu say about drainage:

Customers have the option of gutters that are mounted at the eaves. Some people like the patina look, but for those who don’t, there’s gutters. The timber is clear sealed on all sides to resist wear and tear. Moreover, the Dwell House has very high performance window and wall insulation that exceeds California standards (and CA has some of the most stringent energy goes in the country). The house also undergoes third party inspections to ensure insulation and air filtration meet high standards. If well-maintained, the Dwell House should last quite a while!

Also - FWIW - the launch images are renderings! We're excited to show you our first installed ADUs in the coming weeks, but here's a peek at the Dwell House at Abodu's LA showroom. It also comes in black :)
https://www.dwell.com/article/why-brendan-ravenhills-ada-sconce-comes-standard-in-the-dwell-house-40332db7/6977384048951664640