Want to build ADU in Bayarea CA

[Vipul Parikh]

Hi

I am planning on building a ADU in Union City, CA . I have 8750 sq ft lot and I can build upto 800 sqft of ADU. Here are some of the questions

1. I spoke to the city and got confused on how city permit works. Not sure , if I need to hire a Architect and structural engineer or either will work?

2. regular construction / modular /prefab or premade panels?

3. My property is not square or rectangle shape . It is longer on one side and shorter on other side. Can I still go to modular constructions ? 

4. Is $225 /sq ft norma for modular ?

5. Should I get a architect /structural engineer (atleast 3k) , get a plan made and then get some quotes for regular build ?

6. Any idea on how is prefab / sq ft?

Thanks

[David Song]

I am building one in San Mateo and planning one in Hayward.

Spending about 20k on soft cost in San Mateo, for 640 sf ADU. Close to getting final approval, about 4 revisions, involving architect, civil engineer, arborist, gas line designer, and some other folks. Each city gives you different headaches, forcing you to shed money like crazy.

Plan about $200k for site built, expect rent of around $2500/month, plus appreciation of about $400k, just estimate.

For Hayward, doing a main house expansion (900 to 2000 sf) and an ADU (1000 sf) at the same time. Expect similar soft cost. Architect is talking to city for initial planning and floor plan, etc.