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California allows "granny flats" in backyard of any single family house: would you build one?

Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
The state of California has just passed a law that will allow a homeowner to stick an Accessory Dwelling Unit (ADU, granny flat, in-law unit, casita) in the backyard of their single family house, provided it is no more than 800 square feet, with 4 foot setbacks side and rear, and no more than 16 feet high. It has to follow the normal building code, e.g. plumbing, electrical, fire rules. The city has to approve/deny the permit within 60 days, "ministerially," which means with no discretionary decisions like design approval meetings.

In addition, a homeowner can now turn an existing structure like an attached or detached garage or storage unit into a second ADU.

You could build an ADU for an office, for your aging parents, for your adult kid, to rent out for income, for your guests, for your care-giver, for yourself as you age and can't live in a house with stairs. Would you build one, if you could? California homeowners, will you build one (or two)? Would you/do you live in an ADU, or does your child?
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Replies to: California allows "granny flats" in backyard of any single family house: would you build one?

  • bluebayoubluebayou 26882 replies175 threads Senior Member
    my D lived in one for a couple of years while she was working at Stanford.
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  • sushirittosushiritto 4130 replies12 threads Senior Member
    Thanks for the news. Yes to all your questions, except no garage conversion. A garage is for cars, in my household at least. :smile:
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  • lookingforwardlookingforward 34480 replies382 threads Senior Member
    But there have been many "casitas" in CA for some time, what's different about this ruling? Or was it previously a city by city policy? Think of all the "guest houses" behind the main home, in LA County, rented, not just for occasional use.
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    Previous recent legislation had liberalized the ADU rules, though not nearly this much. In response, businesses have sprung up that will build an ADU or convert a garage and find a tenant for it, with the costs and the rent shared between the builder and the homeowner.

    Also, some builders now have ADU plans and prefab ADUs, so an ADU can quickly and (for California) cheaply be erected. Eight hundred square feet is enough for a compact 2 BR house with a full kitchen, with dishwasher and four burner stove, and a stackable washer/dryer.
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  • WayOutWestMomWayOutWestMom 10244 replies206 threads Senior Member
    edited October 18
    Not in CA, but I was going to build one for my mother when it became unsafe for her to live alone in her isolate rural area. I have a 3/4 acre lot so there was plenty of space.

    (In the end I didn't build because my mother decided she didn't like the conditions I imposed--namely she had to give up her car. Mom was a dangerous driver because she macular denigration. Her license had a bunch of driving restriction which she routinely ignored. I finally called the DMV in her home state and had her license revoked.)

    My older D (also not in CA, in fact not in the US) is buying a house with a separate studio/1 bedroom apartment on the property for me to move into when I get tired of taking care of my big house. She says that co-living is very common where she lives now.
    edited October 18
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  • momsquadmomsquad 1111 replies64 threads Senior Member
    This is a timely question, I have been thinking about this since I heard of the new law. The previous owner of our home liked to tinker with cars, and he built a large detached garage out back. The home was built with a 2 car attached garage, so through the years the detached garage has been known as "the clubhouse", "grandma's room" (joke), and now the "junk room". It has a nice tile roof and electricity but is otherwise unfinished. A contractor once told me it is easier and cheaper to do new construction than try to bring a detached garage up to code in California, so I haven't pursued it.

    Any estimates on what it costs to convert a garage in California? We would need to run a sewer line extension for a bathroom and add climate control.

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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    But there have been many "casitas" in CA for some time, what's different about this ruling?

    A lot. A four foot setback side and rear is much, much more permissive than what was previously allowed in most areas. Also, provided the plans follow the city's listed rules, the city can't say no: previously they could disallow for floor area ratio, architectural review, landscaping, lot coverage or historical resource review, but now they can't. Cities are also prohibited from charging certain high fees that they previously charged.

    So now, it is much easier, cheaper and quicker to get your plans approved.

    For example, this ruling would allow me to stick an ADU in my back yard. (I don't want to.) Previously, the setbacks for my lot were 10 feet on the side and 25 feet on the rear. But now, with 4 foot setbacks side and rear, there's plenty of room for a second little house back there.

    When I tried to remodel my house, my architects spent a year negotiating with the city, where they kept submitting seemingly conforming plans and the city kept saying we couldn't build them. But now, if I submitted conforming plans for an ADU in my back yard, my city would have to approve them within 60 days.
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  • TatinGTatinG 6470 replies114 threads Senior Member
    Defintely, no and I don't think our HOA would approve it. At least, i hope not. Parking would still be an issue. I like my area because it is not dense and overcrowded.
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    I don't think our HOA would approve it.

    They have no say in the matter.

    CIVIL CODE SECTION 4751. ACCESSORY DWELLING UNITS.
    Any covenant, restriction, or condition contained in any deed, contract, security instrument, or other instrument affecting the transfer or sale of any interest in a planned development, and any provision of a governing document, that either effectively prohibits or unreasonably restricts the construction or use of an accessory dwelling unit or junior accessory dwelling unit on a lot zoned for single-family residential use that meets the requirements of Section 65852.2 or 65852.22 of the Government Code, is void and unenforceable.
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  • Techno13Techno13 223 replies8 threads Junior Member
    I wonder how this will work with HOA rules?

    Most CA properties and back yards are not large enough to accommodate an ADU. Our neighborhood was planned such that a certain % of the detatched garages have ADUs above. I only know of one that is occupied. The rest are kids playrooms or man caves. I'm pretty sure that is not the intent of the new law. Second storey ADUs are useless for actual grannys in many cases.
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    As to parking, the city cannot require parking spaces for the new ADU if

    it's within half a mile walking of a transit stop;

    it's contained within the primary house or an accessory structure (e.g. converting an existing garage, attached or detached);

    it's in a historic district;

    it's within a block of a car share; or

    on-street parking permits are required but not offered to the occupant of the ADU.

    Also, cities can't require the homeowner to replace the parking spaces lost in a garage conversion.
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  • ProfessorPlum168ProfessorPlum168 4147 replies88 threads Senior Member
    Absolutely I would, if the cost was cheap enough. The price to extend my house is ridiculously high so I never pursued it.

    I have the space (15K square foot lot, much of it wasted with dead grass. Heck, I would get rid of the swimming pool if the ROI was worth it and I could build 2 of them lol. Anyone want to venture a guess as to how much a nice 800 square foot unit would cost to install in Silicon Valley out the door?
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    Any estimates on what it costs to convert a garage in California?

    I'm seeing ballparks in the $100,000 to $150,000 range, but obviously YMMV.
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    Most CA properties and back yards are not large enough to accommodate an ADU.

    They are now, because you can stick the ADU almost up to the property line. And you can convert an existing garage.
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    Techno13 observes correctly that a second story ADU is not ideal for an aging parent with mobility issues. However, it would be fine for an adult child, a caregiver, or to rent to a student, a young couple just starting out, or a working adult who is looking for less expensive housing.
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  • mathmommathmom 32458 replies159 threads Senior Member
    ADUs are a great way to get affordable housing for people you want to be there anyway, like your recent grad kid or your aging parent. I think they work best in neighborhoods that are walkable and have decent transportation, but generally they don't cause nearly as much extra traffic as the NIMBYs fear. For cities they are a way of generating extra tax revenue without their infrastructure costs going up - no new roads or sewer lines. Okay stepping off my soapbox...

    My BIL in Berkeley transformed a large shed/garage into an ADU a few years ago. They had thought they might use it as an air B&B, but they ended up loving it so much it really acts as an extra family room. It's gorgeous and must have cost an arm and a leg. Very mid-century modern if feel, lots of glass, lovely materials. They had never used it as a garage so they didn't change traffic patterns.

    ADUs are not allowed in our town. (Well if you are in a two-family zone with a one-family house I imagine it might be allowed, but might still need zoning variances as set backs for garages are less than for residences.) I've worked years ago on a project where we turned a garage into an "unheated workshop". We were allowed to fully insulate it and put in a steam shower. My client uses it as an accupuncture/massage studio space. They have portable electric heat in the winter. It's not an ADU because there is no kitchen. It didn't cost that much to run a plumbing line to the garage - there was already electricity.
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  • momsquadmomsquad 1111 replies64 threads Senior Member
    Wonder how Assessor's Office calculates new property tax, do they reassess the whole property or just add the value of the ADU? Same with insurance, does ADU have separate policy? We may just do incremental cosmetic improvements that won't trigger permit requirements.
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    Good question, @momsquad. I didn't know the answer, so I looked it up. It turns out that when the Assessor's Office assesses your new ADU for tax purposes, they add the assessed value of the new ADU to the existing base value of your house. Your whole house doesn't get re-assessed.

    https://maxablespace.com/granny-flat-tax-implications/
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  • sushirittosushiritto 4130 replies12 threads Senior Member
    edited October 18
    Anyone want to venture a guess as to how much a nice 800 square foot unit would cost to install in Silicon Valley out the door?

    If you hired a GC, then about $200-$500+/SF depending on how fancy your fixtures and finishes are. And don't forget to add soft costs like fees, permits, architectural, engineering, etc.
    edited October 18
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  • Cardinal FangCardinal Fang 18409 replies158 threads Senior Member
    Anyone want to venture a guess as to how much a nice 800 square foot unit would cost to install in Silicon Valley out the door?

    A quarter million or more? You could probably get by with less if you went for a prefab, and some of the prefabs look quite good to me.

    I know an architect...

    It's a whole lot cheaper than buying a second house!
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