ADU conversion from recreation detached unit 950SQ


I am about to move in and consider ADU conversion. I am a newbie.

  • Exist recreation detached unit 950SQ with a permit construction
  • 950SQ
  • Half bath and air conditioner exist. heater(?)
  • Investigating permit rule. So far the home in 95124 in San Jose but it state “incorporated” R1-8 zone. I am not sure exactly the rule as incorporated. But the initial design contract told me your home does not qualify for San Jose city rule(removed limit 800SQ) because your home is an incorporated zone. Stated need to following Santa Clara Count rule.


  • What is the general floor plan design cost with submitting a permit, docs fee?
  • What is general conversion cost from the existing 950SQ unit. It has half bathroom so I believe the water pipeline already exists.
  • ADU will have separate water, electricity meter, and post office address? Tenants will directly pay all the utility fee or I pay and request them? Garbage can service will be separate or combine with our main home?
  • Better build the separation fence around the building for privacy? Separate entrance already plans.
  • What other things need to consider?

Any recommendation design or builder contractor is welcome.

Thank you

Just say no to ADUs

Anyone recently completed ADU project in Bay area? Looking for referral GC.

Thank you for the referal. Have you use this builder?

Yes, but this was pre-Covid. Detached ADU in Hayward. Good professional team, responsive, and hand-hold through the process. I believe it was high $200s or low $300s per sq ft costs but it was a while now. I’m sure the price is higher now given labor/material costs.

Good open, modern, clean designs. I want to say they are more middle to upper-mid end but I just needed mid or lower for my situation (average tenants in average areas).

With that said, I would definitely put them in the running among your other referrals.

I just need regular home addition builder not groud breaking build from scratch. Thank you.

Didn’t even realize you were the original starter of this thread. Welcome back…
Is this the same situation from March 2020?

I stopped at that time and now I am seriois doing this.

Do you have plans already? I have a good contractor to build. But if you’re just step 1, he’s not the right guy for the job.

Mostly interior remodeling since the existing unit. I am finalizing my floor plan and will find the contractor and get bid.

Are you considering one of those prefab adu outfits too or only stick build firms?

Where is your contractor located?

He is based in Alameda but does work from Santa Rosa to the South Bay and everything in between if that’s what you’re getting at.

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I have an existing detached unit already. So no exterior change.

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Like I said/ years ago, stay away from ADUs. Cost too much to build…. you will end up with an adversarial tenant in your back yard that will sue you with free legal aid, supported by a government that wants to confiscate your property. Good luck.

I have opposite approach and been actively adding ADU’s to all my properties, when possible. I already assumed everything favoring tenants with rent control, just cause eviction, and etc.

Same shit , just more units. :man_shrugging:t2:

I have ADU at my primary residence. First set of tenants had to break lease when the bf was arrested. :flushed: 2nd set did not renew after 1 year. Current tenants have been with me for over 3 years and pay rent a week early.

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Yup, that was my MO at my Sunset home. Original maid’s quarters unit that was built with original house (you can tell it is legal or original) and then I added the legal rooms in the ground back (separate unit accessible from the side fence door from sidewalk. Those two units alone paid for my mortgage (I lived for free). Sweet 2.5% mortgage is almost paid off in oh 4-5 years. Why pay it off faster right? 2M US dollars should go velly velly far in Malaysia…

The OP waited 2 years to build. Meanwhile the cost of construction has doubled. I doubt if rents have. There are plenty of better ways to spend your money. Do the analysis. Figure out the cap rate and ROI on your ADU. Also figure in the hassle factor. Do you really want a potential criminal, con artist or dead beat on your property in your face?
The sate of CA if sincere about fixing the housing shortage should bend over backwards for home owners that build ADUs. No cause evictions. No rent control. No fees or permits required. No tenant rights. Then maybe and only then would home owners feel safe building ADUs. In reality very few are being built… and mostly by very experienced landlords. I have an existing one on my farm, cost me nothing. Finally got a good tenant after 4 years. The other 3 before were not. One burned down his previous house and was a drug dealer. One bitched at me for a year and a half. And one never paid rent and broke a lot of stuff plus getting the HOA pissed off at me. 1 out 4… go for it if you feel lucky.

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:smile: :rofl: