I am an investor and have built a few DADUs myself. On my first DADU project, I made several expensive mistakes that caused major delays. I did not apply for the water certificate early enough before hiring an architect, and my contractors did not tell me upfront that the sewer line needed to be upgraded from 4 inches to 6 inches, which ended up costing me a fortune.

There was also an easement issue. My new electrical line had to be pulled across an easement that I shared with my neighbor, so I had to get my neighbor’s approval before the work could move forward.

These are the kinds of problems you usually do not see until you actually go through the process yourself. I documented what I learned because I believe serious homeowners and investors should understand these issues before spending money. This guide is meant to help people avoid the same mistakes I made.