We built an ADU in San Diego a year ago and we hired a drafter who specialized in ADU designs. His total fee was approximately $6.5K and the permit fees were $2.7K. I made the mistake of assuming a cost of $150/SF for construction and we originally had a 2 story design (1,200 SF). Once I began getting price quotes from contractors, the cost was $275-$350 per SF. Eventually, we ended up paying $300 per SF for construction. We also reduced the SF of the ADU to 499 SF. We paid cash for the construction and the 499 SF was b/c we would not have to pay additional fees to the city (ie. sewer cap, school, etc).
I'd like to do it again, but this time, I'd do the following:
1. Use one of the pre-approved designs that are available from local cities and make sure that my city will approve their pre-designs.
2. Pay a contractor for his/her time to review the plans and provide a more accurate estimate. I noticed that when I asked for quotes, many contractors didn't want to take the time to provide a detailed line item estimate and I understood why.
3. I should have done more research from the City on how their fees are determined and what fees are triggered based on the size of the ADU.
If you'd like to know more, you can send me a message.
