Backyard Cottages & ADUs

Related Pages: Building Permits ... Prefab Houses

Parent Q&A

ADU — where and how to start? Jul 31, 2021 (7 responses below)
New Berkeley ADU, landlord, Airbnb, pros / cons Jun 15, 2021 (3 responses below)
Wi fi extender or mesh network for ADU? May 8, 2021 (6 responses below)
Pre-fab ADUs Apr 19, 2021 (3 responses below)
What are the steps for ADU Mar 11, 2021 (3 responses below)
Berkeley Home Expansion for Dummies Feb 2, 2021 (8 responses below)
ADU without kitchen? Jan 8, 2021 (5 responses below)
True cost of ADU? Nov 23, 2020 (6 responses below)
Building a small, L-shaped ADU? Nov 23, 2020 (2 responses below)
Architect to help plan an ADU May 6, 2020 (7 responses below)
Experience with pre-fab ADU Oct 9, 2019 (1 responses below)
ADU Project -- Contractor Selection and Negotiations Jul 5, 2019 (4 responses below)
Tax implications of building an ADU in Berkeley Oct 9, 2018 (6 responses below)
Prefab for ADU? Sep 20, 2018 (1 responses below)
Converted Horse Trailer in Back Yard in Berkeley? Sep 6, 2018 (1 responses below)
Accessory Dwelling Unit designers/architects Aug 12, 2018 (8 responses below)
Small shed in backyard, now Berkeley wants to call it habitable Dec 6, 2017 (4 responses below)
Pre-fab in law Jul 19, 2017 (1 responses below)
  • ADU — where and how to start?

    (7 replies)

    We have a dilapidated “garage” which turns out it was never a garage but a carport that the previous owner put up a wall to enclose it. concrete slab is torn up and in a bad shape. Water seeps in from the uphill neighbor. It’s where things go in to become garbage. I am afraid to go in because of rat poop and dust. Dark, dingy, dusty and a real mental drag.  I dream of turning this into a bright and usable space. An enclosed and weather protected storage would be fine but it would be amazing to have a flexible space for working from home, guest bedroom or dare I dream, a family play space. As we are cramped in our small 2 bedroom house with no storage space and small backyard, I look at this wasted space and get frustrated that it isn’t more useful.

    I have no idea where to start to make my dream a reality. I don’t want to start meeting with architects when I don’t even know how much I need to budget. I don’t have hundreds of thousands of dollars just sitting in the bank, so I would like to have an idea of how much something like this costs so that I can start saving for it and figure out how to come up with the funds. Do people just borrow against their current equity?

    Moving to a bigger place will be easier but I think that might be more expensive. We are in Oakland and I don’t think we want to move to Antioch/Clayton or beyond to get a house we want within our budget.  But I don’t know.

    I think I need a designer / manager who will guide us through the entire process (land survey, permit, etc) But I don’t even know what I dream of is possible. 

    Any tips on where to start would be very much appreciated. 

    If you want to ball park, I would apply a cost per sf calculation to your garage size. So if you have 500 square ft at $600/sf its a $300 job. I'm not sure what current prices are per square ft but I wouldn't be surprised with the current environment if its around $600. Also if your garage isn't a permitted garage, you may have issues getting an official ADU permit and will have to go the much harder route (aka more $ and time). 

    Hi there. I live in Oakland and had a similar situation - a garage that was too small to park in, filled with junk and also rats. The floor was sound and so was the roof etc, so the structure was ok. I converted the space to a “bonus room” - really a family room which we badly needed. I used a structural engineer, a licensed contractor and myself. No architect. I wanted it to be permitted but the ceiling slopes too much and I needed to keep my WD up there, which would not have passed the permitting. So we just did everything rigorously to code, took pix of the process (for a future buyer). Btw I’ll give you 2 pieces of advice. I wanted to add a duct to heat the space from our main heater, but I spoke with several heater guys and they said that will not be approved bc Oak fears you’ll make it into a multi family dwelling. So we installed amazing little wall heaters that look and work great. We had to add a new circuit. Due to the slopes ceiling we also stumbled with insulation - code is confusing. In fact much of what you read online is wrong for alameda county. I consulted about 6 insulation companies and went with foam in the correct R that meets code. I recommend foam if you raise the ceiling. Also btw before even starting this I spoke to several local realtors to get their take re resale, which is what will eventually matter. All said go for it. I kept the space easy to convert back to a garage (just change the door), and right now we are very happy with this decision. The total cost has been about $22k for a playroom with around 180 sq ft. It might have cost $27k if we’d done it with permits. 

    East Baker Construction does just that. They came to our house and had incredible suggestions and forethought. We aren’t ready to do everything yet since our toddler is giving us a run for our money. East Baker is new so their availability is good and they’re competitive in costs. 

  • I'd love to hear experiences from people who have a relatively new-construction ADU (2018 or later, that is banned from 'short-term' rentals), as we are considering a detached (or attached) ADU on our large, primary residence. SFU lot (in addition to a small home addition). My understanding right now is that

    - we would not need to register as landlords (2021 update)

    - we would be exempt from rent control

    - we would not be required to provide an additional parking space

    My questions are

    - Berkeley ADU law says can't be rented out short-term. OK. But ADU 2021 Guidance says not for less than 30 days ("ADUs and JADUs shall not be utilized as
    commercial short-term rentals (i.e. rentals less than 30 consecutive days)", and short-term rental regulation talks about short-term rentals being less than 14 days ("If you rent your Dwelling Unit, authorized Accessory Dwelling Unit, or Accessory Building, for 13 days or less, you are considered a Short Term Rental and are required to register with the City based on Berkeley Municipal Code (BMC) Section 23C.22"). Which is currently being enforced? How are you implementing this? (We were told by an architect that we could, for example, rent through Airbnb as long as our rental was set to 14 days or more.)

    - What are the pros / cons of renting (for either >14 OR >30 days) your ADU? What is it like to be a Berkeley landlord of new-er construction? Do you use Airbnb? Other more or less traditional ways of connecting with renters? I'm familiar with Airbnb as I'm helping host a property for my mother (not in Berkeley), and I like the idea of renting through them. But am open to all the options...

    - We would likely need to use a HELOC to (help) fund the ADU construction. What are your experiences with ADU rentals and income covering costs. In other words, what are your net profits like? Ours would likely be a studio (or maybe one-bedroom) in South Berkeley. What should we expect or be wary of?

    - What do you wish you knew before you decided to build a new ADU? Would you do it again? Why or why not? Other thoughts?

    Thank you!

    Under Berkeley rent control laws you can't rent to anyone for under 14 days because that's a short-term rental. But as soon as someone living in your ADU (or even your own residence) has stayed past 14 consecutive days they have the rights of tenants. 

    There is no way to rent anything out in Berkeley for any number of days without either breaking the law or putting your property rights at risk. You can't even let a good friend or family member stay with you for a month rent-free without inadvertently turning yourself into a landlord who is now unable to move that person back out.

    This is how our rent control board has destroyed the city. Their efforts to "protect" housing for renters causes everyone to remove their units from the market leaving us each year with fewer available rentals.

    Hi, hope some of this will help.  You would be fully exempt from both rent control, and eviction protection, and do not need to register your unit with the Rent Board.  When we built our ADU in 2018, we had to sign a form saying we would never rent it via AirBnB or the like - I’m pretty sure this is still a requirement (though not 100% positive on that one.  I think only older ADU’s can be rented short-term, not newly constructed). I’d suggest including a washer/dryer, and a one bedroom rather than studio if space allows. Pre-COVID, renting in Berkeley was good (for those of us exempt from Rent Board regulations); it has become harder just like all of the Bay Area has.  Highly recommend joining BPOA - Berkeley Property Owners Association. Good luck to you. 

    What is it like to be a Berkeley landlord of new-er construction?  IT SUCKS!

    As you are figuring out, this is complicated.  According to the CoB web site:

    You cannot use a unit as a short-term rental if it:
      is an accessory dwelling unit that:
        was built after April 1, 2017

    Have you read about str on the CoB website?I don't think you can do it.

    City of Berkeley is cracking down on this. They are actively searching through AIRbnb's listing looking for non-permitted/non-registered units issuing fines.

    The political powers at the City right now are all about catering to the homeless and renters.  If you build an ADU they want to make sure it will be a long term rental for lower income/homeless.  Are you preparing for the new laws the city is about to pass which are NOT favorable for property owners?

    Read up on HELOCs, If interest rates increase you could lose your home.  Be very careful about the terms of the loan.

    AIRbnb is not as easy or trouble free as people say and think.  Yes you have the potential to make more money, but it also takes a lot more of your time to manage.  Depending on time of year and location, you might have long periods where you might not have guests.  For Berkeley budget/expect a 50% vacancy rate.

    Something else you need to consider is rents in Berkeley are 20-25% below pre-COVID rates.  If you rent now the Rent Control Board limit's the amount you can raise the rent every year.  If rents recover it will take you 25-30 years just to get to pre-covid rental prices.  Berkeley Rent Control laws are why people in Berkeley have a 2 bdrm apt for $750 per month.

    With COVID everything is out of wack.  No one knows if things will get back to normal or if one of the new variants are going to shut things down again.

    Best of luck

  • Wi fi extender or mesh network for ADU?

    (6 replies)

    Hi all, Wondering if anyone has recommendations for a device that would allow us to share wifi with the cottage in our backyard. Seems like these extenders are designed for larger houses rather than separate structures but wondering if anyone has experience with it working in a backyard cottage. Lot is only about 4500 sq feet total, so the distance from house to cottage is pretty short. Thanks! 

    Hi, when the pandemic started it became immediately clear that our  WIFI system wasn't going to work. I invested in the Amplify system

    it extends from the middle room of my 1300 sqft house to my driveway where i have a trailer as my office. There I am able to Zoom with perfect clarity! I bought the whole system and a new modem at Best Buy.

    We used Eero Pro 6s for this type of thing and they worked well. You may need to buy extra in order to place one at the closest point of each building.

    Not exactly what you asked, but we were in a similar situation, switched to Sonic (without an extender), and the issue went away. We were originally using Comcast. 

  • Pre-fab ADUs

    (3 replies)

    Hi everyone, 

    My mother is looking to build an ADU in her backyard in East Richmond Heights. Does anyone have experience with pre-fab ADU companies such as Habitat ADU? It seems attractive that they take care of everything but we do not know anyone in the East Bay who has utilized such a service. Any personal experiences or advice would be appreciated. Thanks!

    RE: Pre-fab ADUs ()

    We looked into Connect Homes for a while. Seems a good operation, they do operate in the Bay Area. We toured a sample home in Orinda and it was pretty nice.

    RE: Pre-fab ADUs ()

    We talked to habitat adu, they build in east bay. Unfortunately, they weren’t able to crane in our property because of tree and electrical lines. We also talked to abodu but they quoted about 80,000 over they’re starting price of 199,000. 

    RE: Pre-fab ADUs ()

    Please contact Contra Costa County DCD for current permitting information.

  • What are the steps for ADU

    (3 replies)

    I looked at the city website and found a prepared PDF file explaining REGULATIONS regarding the ADU.

    1) I was wondering if I should get a permit with City of Berkeley, before I build/design the ADU

    2) What is the contact information in the city of Berkeley who can guide/approve me through the process.

    Thank you

    RE: What are the steps for ADU ()

    You need to have a design to submit in order to get the building permit. So you should do that first. Find an architect or a design/build firm with experience doing ADUs in Berkeley (so that they know the regs). They should be able to guide you through the permitting process. 

    RE: What are the steps for ADU ()

    Yes, you need a permit no question (unless you are considering building illegally, which of course introduces problems you probably don’t want...) The permit process is a bit complicated; sometimes described as a nightmare actually. This has changed a bit since they are supposed to be encouraging ADU’s to be built. You can certainly file the permits yourself, but I think the norm is that the contractor will file them, and then of course the contractor deals with them on each step of the process where the permits are required (scheduling the inspections at the job site; corrections or changes after inspections, etc.). So the “guiding” is not really on you; it’s on the contractor, who knows it like the back of their hand. Try to hire an ADU builder who has experience building in the City of Berkeley. Two other unrelated suggestions - join BPOA, and familiarize yourself with the Rent Board. Your unit will be exempt due to the passage of Measure Q (or if you happen to be a Golden Duplex), but the Rent Board attempts to steadily erode this exempt status - good to pay attention to it. Good luck!

    RE: What are the steps for ADU ()

    I went through the process about ten years ago, and built my accessory building. There were two stages then. Zoning stage followed by building permit stage. I managed the zoning stage by myself, but definitely needed architectural plans complete with engineering calculations, and lighting calculations to get approval for the building permit.  For the zoning permit I needed the footprint of the building, the height, lot coverage, etc. There have been many changes in ten years, however.

  • Berkeley Home Expansion for Dummies

    (8 replies)

    Hi all, we are contemplating expanding our Berkeley hillside home to add ground-level bedroom, bathroom and (attached or detached) plus room. The things driving this are very time-sensitive and I’m wondering what I should know about the process before we launch it so as to make it as speedy and efficient (for Berkeley) as possible. What we have so far: a basic set of plans by an architect relative not licensed in Berkeley. Aside from speed, I’m also curious about any local quirks or pitfalls of this process worth knowing about, and how it may have been affected by Covid and the economy.

    One further consideration: we have a difficult neighbor.

    I would welcome your thoughts and experience, especially if recent.


    Bursting At The Seams

    Hi I'm not an expert but from my experience with recent construction on my home, getting permits in Berkeley is an arduous and slow process. It is even slower now because of COVID-19. It can easily take 6 months +  just to get the permits to start construction (in my own experience and based on what I've heard from others). If you want to get things rolling, I suggest talking to a local architect who has plenty of experience with Berkeley permitting. They can review your plans to make sure comply with your home's zoning requirements and put together a plan set that complies as much as possible other berkeley requirements. They can also shepard it through the permitting process. Things that you might want to ask the architect about are getting a survey asap and any other consultants that are required such as structural engineers etc. Everyone in construction and construction-adjacent businesses is  busy right now - it can be hard to find people who have availability on your timeline so this can end up being another source of delay. Once you have a clear idea of the plan, it will be a good idea to get a contractor to get on their calendar well in advance to try to avoid delays in starting construction. Good luck! (And sounds like congratulations are also in order!?!)

    I have heard that getting permits for ADUs is really fast. You may want to add a tiny kitchen. 

    Hi there, we're almost finishing an addition in Berkeley. We used an architect with limited experience and it showed during the entire process. (I believe we interviewed 5 architects). It took longer (it was more affordable) and we had to submit revisions and further studies until it was ready to break ground. In summary, it took 2 years until we started the project. Covid has been hard because the planning office is not open, you cannot go and check with the inspectors, and you depend on the city employees to get back to you; however, we can't complain because they've been diligent and there have not been any delays because of them. Pitfalls: we had to hire a soil engineer and redesign the foundation. That cause a delay in the project when it was underway (we lived in the house during construction). My only tip, get a great contractor that knows Berkeley. That will be helpful. Take your time on this. We interviewed/contacted 7 or 8 contractors, and we couldn't be happier with our choice. Regarding the "difficult neighbor", people do not like changes. I had to ask for signatures from my neighbors, and all of them but one signed the "no objection" when I knocked at their doors. This one neighbor asked for a specific meeting and she made tons of "intrusive" questions, but I was able to understand her concern (new windows and eventual shade on her property) that were addressed in our meeting. Good luck!  

  • ADU without kitchen?

    (5 replies)

    I read in the Oakland zoning regulations that an ADU has to have a kitchen. Now, we want to build a detached little "cottage" in our backyard that only has a bedroom and a bathroom. It's just for when my mother or MIL visits for an extended time (new baby took over the guest room) and would not be rented out. Would that still be considered an ADU? Or does it have a different name? Does it have to be permitted as well? I mean, of course we could add a small kitchenette, but why invest in something that's not needed?

    RE: ADU without kitchen? ()

    We built one in Berkeley but the learnings are likely the same for Oakland. The ADU's process is more streamlined than regular building permits because cities are trying to encourage building of ADUs for Long Term housing. You'd need a kitchen if someone wanted to rent it as their home, so for your building to be streamlined through the ADU process it has to have all the bells and whistles required for a long term rental. Even if you never plan on renting it, if you want to get the streamlined ADU process you'll have to abide by the ADU rules. You can always do one without the Kitchen, but you will be put into the regular permitting process and have to abide by a lot of extra regs. 

    RE: ADU without kitchen? ()

    My understanding is that regulations try to encourage building ADUs because they can be used as permanent housing, which we sorely need more of. (Even if you don't use it that way, a future owner could.) Not sure if Oakland is the same, but in Berkeley you can build an accessory building (I think it's called) without a kitchen - the permitting process is harder, but it can then be short-term rented (which an ADU cannot, at least in Berkeley). You could put in the most minimal kitchen possible just so it will pass inspection, and then remove it. Probably just requires a sink and some cooking surface. 

    RE: ADU without kitchen? ()

    Hi, it’s written pretty clearly in the Regs that a newly built ADU must have a kitchenette; in fact, that’s the one requirement that crosses over all types of ADU construction. So I doubt you would be able to build one without it.  I’d suggest that it may not be a bad idea at all; your use of the cottage may change over the years. And I strongly suggest hiring a licensed contractor. Very strongly. More info here:

    Recently built ADU owner 

  • True cost of ADU?

    (6 replies)

    We've rented in Oakland for years and are now looking to buy a home here, with the plan that my parents would live with us in a second unit/ADU. True duplexes seem to be a little out of our price range, so we are looking at various types of set ups - houses with large flat lots but no second structure, houses with partial ADUs (garages converted to studios that could be expanded, etc), houses with large lower levels or extra rooms that could be walled off and a kitchen and bathroom added. We're having trouble figuring out what the true cost of an ADU will be and with such a fast-moving real estate market we can't really get actual estimates on a specific property or anything like that before buying. Whether or not we can afford any given home depends on how much adding the ADU would cost, so I would love to hear others experience on how much it cost for them to add one to their home. I'm particularly interested in garage conversions and also in pre-fab companies like Bay Modular which seems great on paper but wondering if costs can add up and how to avoid that. Contractor recommendations welcome but at this stage I'm really more looking for actual cost examples so I can get a sense. Thank you! 

    RE: True cost of ADU? ()

    Our garage conversion, about 600 sf with 400ish to be a studio apt, the rest storage, has been estimated at 200-300k. That's not including the architect and permit fees, on which we've spent a few thousand. The garage has a usable foundation and drainage system, so it would cost more if we needed to build those. (This is in Berkeley, but I'd guess Oakland costs are similar.)

    RE: True cost of ADU? ()

    I personally haven’t added an ADU to my own home, but we’ve done many renovations and I’ve worked on several projects adding units to properties in Oakland and Berkeley and am familiar with the budget.

    I haven’t used any modular construction, but took a quick look at Bay Modular. The $250/sf cost for the largest unit is about as good as it gets for construction costs. However, this doesn’t appear to include the foundation which can be a significant cost.

    Other expenses not accounted for as far as I can tell are a Survey, Geotechnical Report, Permitting Costs, EBMUD water meter and service, PG&E meter and service, sewer lateral, structural engineer for the foundation, etc. The sum of those costs can easily add up to $75-$100k. If you can get away with sharing utilities with the existing unit, you can save quite a bit, but in my experience the local jurisdictions won’t allow it. YMMV

    Chopping up an existing house or remodeling a garage area can result in some significant cost savings. But this scenario would rely on everything existing being in good condition and would be very location specific.

    I personally would budget at least $250k for a freestanding ADU. Possibly more. Which is why we haven’t built one.

    RE: True cost of ADU? ()

    I think this is dependent on the site. New construction or remodel, extent of work, location, grade, access, etc. I was looking for a house earlier this year with plans to live with a sister who is disabled.  Not the exact same situation but also a value-oriented home buyer willing to consider a project. What was most helpful was meeting up at the house with a contractor for his opinion. That contractor was a family friend so not his usual business but you might try calling around to see if someone would be willing to meet you at a property for a quick informal bid. This is obviously only for properties you have pre-screened to be of interest. Might be considerate to offer a consult fee.

    Another way to do it would be to video your walk-through and send it to the contractor for their opinion. Also your real estate agent should be able to give you a ballpark figure too and that info is useful when comparing properties.  Either way I think you will need to get quotes specific to the property. Good luck! 

  • Building a small, L-shaped ADU?

    (2 replies)


    I am toying with the idea of building a small ADU in our back yard. I want to build a 1 bedroom ADU with a kitchen and 3/4 bath, and it has to be L shaped for our lot.  I also want a loft above the bathroom/closet area to be additional space for kids to sleep.  With all those desires, it's hard to find a prefab that would work - but does anyone know a prefab company that might be able to customize this? Or have a firm they recommend to design/build one? I'm looking for something on a moderate budget. I've seen some designers that build ADUs for an average of $385K that is out of my range...

    That was my conclusion, too, that prefab wouldn't work. We are building it in the regular way, and it will be in the range you described. We plan to get a loan and do it!

    We've been getting bids to build an ADU during the past year. First of all, check the regulations for ADUs for your city so you know what you can and can't do. For example: ADUs must have a full bathroom;  you can't do a 3/4 bath.  There are strict height and square footage requirements too.

    Here is what we found out about pre-fab ADUs:  The reason they are cheaper is because one size fits all - economy of scale.  What they sell is what you get.  Some firms manufacture the pieces and deliver them to your site on a flatbed truck or with a crane.  Other firms sell you a "pattern" that you pay someone else to build. They might have network of contractors that they will recommend or you might need to find one yourself. A big expense will be site preparation, which is not included in the price of a pre-fab ADU. Creating a level spot for your ADU could cost a lot of money.  Also I found that pre-fab ADU companies seem to come and go.  Over the course of a year researching ADU's, I found that websites would suddenly disappear - even the ones I had read about in trustworthy articles and online reviews just a few months earlier.  So make sure you are dealing with a firm that has been in business for a while and has good recommendations, and that is experienced building ADUs in the Bay Area.  

    After we paid an architect and started taking bids from contractors, the biggest shocker for us was the cost of preparing the site. Our backyard is not completely flat, and it's not super easy to access, so it was going to cost a lot of money to excavate it, haul away rock and debris, and put in retaining walls and drainage. The bids we got were in the $500K range for a 500sf ADU because of the site. In the end we decided not to go ahead with it.  I would recommend that you talk to an experienced local ADU designer, tell them what your budget is, and see what they recommend.

  • Architect to help plan an ADU

    (7 replies)

    We are looking to build an ADU on our property. We have a license contractor and have an idea of how it would look, but would like to hire an architect to draw up plans only.

    Can anyone recommend someone who could do this?

    I can recommend Jay Castle of Meshwork Planning and Design.  We are in Berkeley, working on ADU, and have hired Jay.  He's been a great communicator (even during quarantine), understands Berkeley codes, etc., and very open to collaboration with homeowners.

    We used the best architect for our ADU. He was professional, super reasonable and super experienced. He has done multiple ADU’s in the east bay already so it was helpful with someone who had experience and didn’t look clueless. Highly recommend. 
    his website is and he is located in Berkeley. 

    good luck! 

    I have worked with Erick from Innovative Construction & Design before and highly recommend him for your architectural needs. You may reach him at 510-289-5516 or email: archdrafter [at] Good luck on your project! You can let him know Elizabeth from El Cerrito referred you. 

  • Experience with pre-fab ADU

    (1 reply)

    We are considering "building" a pre-fab ADU in Berkeley and would love to hear from anyone who has done it. What are the pros (other than cheaper and speedier) and cons? Anyone have experience navigating the permitting process in Berkeley?

    Thank you!

    RE: Experience with pre-fab ADU ()

    I serve on the East Bay ADU Task Force and Nov. 9th is both a date to tour ADUs built in the East Bay (10am-1pm) along with an afternoon workshop at the Fruitvale Library. At first glance pre fab ADUs seem like a bargain and time saver. If you have a large flat lot with easy accessibility it may be an option. Trouble is most of us don't. SO a panelized prefab has a better chance of being able to get moved into a back yard than a fully built one.The cost of the approved foundation & utility connections are a significant portion of the expense. As of Jan 2020 you would need to be certain that the pre fab ADU meets NET Zero construction standards as well.   A number of builders explored pre fabs early on but walked away from them as the confines and shapes of our yards differ too greatly to make the same ADU work.  Overall the savings has not proven to be significant so best to go with something designed for your specific circumstance.  

    Best to start with imagining the various uses over the course of the next decade as ADUs are truly an amazing flexible use space for extended family, aging individuals (ADA friendly) , guest space, close friends, etc that can also provide significant income should this be a desired outcome.  Governor Newsom also just signed into law the ability to build 16ft high so now additional sleeping lofts can provide extra space. Hope that helps!  Rolf 510.540-1111

  • Dear community! I am about to embark on a basement ADU and attic development project that is going to be quite substantial in cost and complexities. Naturally, I would like to keep costs down. I am looking to learn from your experiences around sourcing and project management for this sort of undertakings.

    For example:

    • Searching and identifying (short listing) contractors -- Where did you search, and how did you go about evaluating qualifications to meet the needs of your project? Did you send out a questioner to contractors?
    • Negotiations -- Requesting / receiving bids and cost negotiating – what was your process? How many proposals did you solicit? How did you compare and analyzed the bids? Did you negotiate the cost? Why or why not? What was your approach / strategy? What was the contractor/s reaction (willing or unwilling to negotiate)? What were the biggest challenges and what were the end results of the negotiations (lowered by x%)?
    • Contracts and timelines – Did you negotiate the terms and timelines? Did you write a formal contract? Did you consult with a legal professional, used a template, or just worked with the documents provided by the contractor? In retrospect, do you feel a more binding/stronger contract could have spared you some headaches?
    • If you chose not to negotiate (costs and/or terms), what drove that decision and what were your concerns (harm future relationships, uncomfortable negotiating, no time, stressful, lack of expertise, lack of resources and tools, other)?
    • Project management – did you hire someone to manage the project? Did you do it yourself? What drove either decision? Are there any online tools you can recommend? What were your biggest lessons-learned?
    • At the end, are you satisfied with your process and the results of your project management and negotiations approach? Did you enjoy it and would you do it again? Why or why not? Did you use any online tools that you can recommend? If you had to do it over again, what would you change?
    • In general, where were your biggest challenges, and what would you do different next time? What tips and advice can you share.

    Any and all advise, tips and insights you are willing to share are GREATLY Appreciated!

    Thanks! Nervous First Timer

    Be very careful.  We went through this whole similar experience about this time last year.  Of course costs are always a concern, but what really put the kibosh on our project was the various and byzantine permitting process from the City of Berkeley.  They were in the process of changing their guidelines/etc., and each contractor we spoke to made it sound WAY TOO EASY or WAY TO DIFFICULT to navigate the process, which, apparently, could be costly AND THEN the application for the ADU could be rejected...It simply wasn't worth the aggravation.  Furthermore, in seeking someone to work with, we were disappointed by Design firms, building firms, and Design/build firms, which we thought would really offer the best option-- it turns out that even the Design/Build people were subcontracting out, and we were paying extra administrative fees right and left.  We finally decided it was NOT worth our while (or sanity) to continue this project.  Even professionals who came to us via friends' referrals, ended up being unacceptable. : (

    On March 9, 2019 at the Rockridge Library, we attended ADUs in Oakland presentation. 

    The Oakland Rent Board, Oakland Permit Department, City of Oakland representative plus two private facilitators (Loni Gray and one for Oakland and the other, for Berkeley [I believe]) and contractors, lender and architect who are familiar with the ADU process. 

    After this 2 hour meeting, our family will be making appointments with architects and contractors who have done this sort of work to get estimates - basement, small cottage or modular?   We will also make multiple trips to Oakland and Berkeley to find out what the permitting process is and whether or not our ADU will be rent controlled [we'd like to rent it out until we actually need to use it]  Loni Gray led the ADU Seminar last November and intends to have more --  On March 25, Loni and her group held an ADUs in Berkeley presentation.  The name of Loni Gray's group is ADU Task Force.  They are a volunteer organization, but well informed.  

    I am not going to be able to answer all those questions, but I will provide my thoughts/opinions on a few. I asked friends and neighbors for suggestions. If I saw a contractor in the neighborhood, I asked for his/her business card. Get at least three bids. The lowest is not necessarily the best choice. Contractors are very busy; the good ones are booked out several years. You are probably just going to have to accept any bid they provide and be thankful you found someone to do the job. No negotiations. Whether to manage or not depends on your comfort level and your knowledge. Can't give advice on that. But no matter what, you have to keep an eye on the job and make sure that the work is done to your specs. Contractors and subs do stupid stuff to cut corners. Watch out! I love using the space after the project is done. I enjoy it everyday. So, yes, I would do it again. Be aware, that some contractors and subs will take the job and start on time, but they are working three jobs, so are only on yours part-time. Very frustrating! Also, don't pay too much upfront. There are laws about that. Google it. Some contractors take the money and run. 

  • Does anyone know whether building an ADU in Berkeley triggers a re-appraisal of the home/consequent tax increase? To the best of my googling abilities it appears the answer is "no" and it seems like not many people would build one if it did, but I would love some corroborating information! Thanks!

    I'm curious what the other replies are. Last time we pulled a permit for a kitchen remodel, I got a questionare from the Assessor about the improvements. I would think building an ADU would least require the value of the ADU is added to your assessment. (<- note that New Construction triggers something, but did the ADU ordinance exclude supplemental assessments?)

    This is what I was suggesting - phrased better from a Santa Cruz guide to ADUs

    " The base value of the land and existing improvements will remain unchanged, and an increment
    representing the change in property value because of the new ADU will be added via
    a supplemental assessment. (See your property tax bill for information on the current
    assessed value of your property.)"

    I built a 1BR/1BA ADU in Oakland (Alameda County is responsible for assessments, so your experience in Berkeley should be similar) and had my property assessment increase by about $125k.  The ADU replaced the detached garage that had been on the site (same square footage) and was done with permits, which triggered the county sending me a form to describe the project.  I spoke with the assessor's office after receiving the increase, and the person handling my file stated that they use a formula to determine the increased value of the property and that my increase was consistent with adding an additional bedroom and bathroom.  Considering the cost of building the ADU and my perception of the ADU's effect on the value of my property, it seemed like a fair assessment and I didn't challenge it.  Prop. 13 limits the county's ability to reassess, so they are not allowed to undertake a full re-appraisal of the home just because you build an ADU.

  • Prefab for ADU?

    (1 reply)

    We’d like to build an ADU in our yard in Berkeley as economical as possible. We spoke to an architect and by her rough estimate, we could no where near approach paying for it.  But I’ve read the archives and it sounds like a few people have opted to do a prefab with a contractors help as a more affordable option.  Has anyone had experience doing this and if so could you give me some details on which prefab you used, which contractor, the budget, and how you navigated the permitting process in Berkeley?  I understand they are making it easier but after speaking with the architect the process still sounded pretty involved and complicated.  

    RE: Prefab for ADU? ()

    Both connect homes and plant prefab are good prefab options. 

  • Hello,

    I'm new to BPN and have a question to ask about parking a converted horse trailer in my back yard.

    I live in Berkeley and am a mum to three kids, and have a cousin's trailer I would love to use in the backyard for a work studio.

    There is no plumbing or electricity (although I could hook it up to our house via an extension cord) and the trailer is 6 ft wide, 19 ft long and 10 ft high.

    Does anyone know about what rules and permits there are for Berkeley on this matter? 

    I've looked on the city website and can't seem to make much sense out of it, am wondering if anyone has experience with this sort of thing that they can share?

    Thanks for your time

    A quick google search shows: 

    Any structure greater than 120 square feet requires a building permit. Accessory structures, including storage sheds, workshops, gazebos, cabanas, garages, carports, wheelchair ramps and similar structures, may be exempted from building permit requirements if the structure does not exceed a floor area of 120 square feet and is not more than one story.

    Even though a building permit may not be required, all structures must meet zoning requirements for use, placement on the parcel, height and size, and building code requirements.  If the structure meets all zoning requirements no zoning permit is required. If a zoning permit is required, talk to a planner at the Permit Service Center or call 981-7410.

  • We are interested in turning our old shed into a living space for a family member. We are looking for an architect who has strong experience with accessory dwelling units (ADUs). If the firm is connected with a construction team, even better. Please let us know if you have any suggestions. Thanks!

    We met with HDR Remodeling and really liked them. 

    However, we didn't end up going through with them because we decided to go another route with our ADU.

    Hi, I highly recommend Levitch Associates. They are a family company based out of Berkeley since the early 1960s. They are a design/build company so they can do design and construction or one or the other. They do beautiful work with meticulous attention to detail. I'm happy to talk about them in more detail, please feel free to contact me.

    I am about to break ground on an ADU in Oakland. I have been using Nathaniel Muhler as my architect, and I would recommend him. (510)295-7092 We are pleased with the design. He has done a few ADUs, I believe. It's a long and complicated process, and he has been helpful navigating all the ins and outs with the city. Good luck!

  • We built a shed with a deck off one corner in our yard last year under the requirements for appropriate shed size (under 120 Sq foot). We did not get it permitted because the code in Berkeley says if it is under that size and under 12 foot average height, you do not need to permit it. The shed was then painted with some windows and a large door. Now the city of Berkeley says we can't have a shed be "nonhabitable" if it has windows and a deck. They are considering it "habitable" because of this and want a building permit. There is nothing in the code that says this (if it has a deck or windows it is considered habitable) ANYWHERE. literally nothing. the shed is exactly that, something where our crap is stored, no one sleeps or stays in there, we do not rent it out, we do not spend time in it. But the city wants it permitted as a "habitable" structure because it looks nice and because there is a deck with windows. It is bogus. When we built it we asked all our adjacent neighbors if they were ok with it and everyone said yes.

    The shed will not stand up to building code, it is not built to live in! It would have to be completely remodeled for tens of thousands of dollars if we wanted to do that. Has anyone else dealt with this? We are at a loss. 

    I am not sure who is telling you this since you didn't go through the permit process - an inspector making a spot house call? Weird, and that means yes one of your neighbors reported you. I would contact your councilmember's office for assistance, and include the code section that says under 120 sf is exempt.

    Hi, I'm a GC in Berkeley, build outdoor structures, treehouses, some sheds, decks, etc. I don't know if I can help you right off, I've never heard of the building department (in berkeley or anywhere) come up with such requirements, ie no windows. If I may ask, how did they recome aware of the situation? If you don't know, it sounds like it could have been a neighbor complaining. I build treehouses with windows, as long as they're less than 120sf and not over 12 ft high, I don't worry about it. Very interested in knowing more.

    I'd send them a copy of their own building code and notate that there is nothing in the code about a shed having windows and deck around it, it must be permitted.  Seems unfortunate that the CoB is going to lengths like this to harass people who have tool sheds.

    Wish I were an attorney to give you a more concrete strategy, but like you said, this is bogus.

  • Pre-fab in law

    (1 reply)

    Does anyone have experience with installation of pre-fab units? We are interested in installing a unit in our yard with a studio and bathroom. Hoping someone has recommendations for a company or any other insight which would also be appreciated.

    RE: Pre-fab in law ()

    Hi, we asked a similar (ish) question on BPN several years ago, and someone responded that they had used a backyard shed (by I don't recall the company name) and hired a contractor to "upgrade" it, and liked it - you might look for that older question and replies. Would have been asking about ADU's, backyard cottages, or granny flats. 

    We've now started down that road, but are hiring a contractor to do a design/build for us (so not a fancy shed). Just at the beginning of the process, so no real insight to give. There are a couple of pretty high priced companies that specialize in the burgeoning ADU scene; we found one who charges less; the proof will be in the pudding of course once the unit is built. 

    I recall we found a company or two that specialized in the "prebuilt"; the name Summerwood comes to mind. But it was hard to figure out where we might see their models, visit an already-built structure, and determine whether savings would actually accrue by going prebuilt. We are happy to be using a design more of our choosing. At the time, googling prebuilt backyard cottages found quite a few options; fewer that worked in California 

    Best of luck in determining which way to go. You are joining LOTS of families doing the same thing in Berkeley now.  

  • Hi, we're considering building a backyard cottage in Berkeley,  and are seeking information regarding if and how rent control might impact this decision. Does anyone know for sure?  We've heard all types of conflicting information, and can't get a response from the rent control board. Can anyone help?  Have you recently built and rented an ADU, and did anyone set limits on the rent you could charge?  Any recommendations for groups or organizations that can help new landlords?  Appreciate your thoughts, recommendations, and information. 

    When I looked into it in the last couple of years, ADUs in Berkeley are not rent controlled. There are a lot of requirements about who is allowed to build them and how they're built (off-street parking, set back from property lines, etc.), so definitely look into that. Also, the rent control board always seemed to respond pretty promptly to any questions we had. Have you tried calling them?

    New construction is exempt from rent control but no eviction control. You can't give the tenant 30 or 60 days notice to move without good cause, but you can raise the rent so high that they decide to move. Here is a list of "Partially Exempt" rentals:

    New construction must be COMPLETELY new, from the foundation to the roof. Do not convert a garage if you want to be able to raise the rent. In addition, you are free to charge whatever you want at the beginning of each tenancy. Rent control only applies to sitting tenants. 

    I suggest you join Berkeley Property Owners Association. You may also want to contact Michael St John for advice.

    I am working with a client on the same issue. It is my understanding that you will need to register the ADU with the rent board but it will not be under rent control regulation. You are not supposed to use it as an AirB&B or short-term rental but can charge any rent you want.

Archived Q&A and Reviews


Have you researched or built a backyard cottage?

Jan 2014

Hi, we're considering building a backyard cottage (ADU), in Berkeley. This would be both an income-generating prospect (hopefully), and possibly a home for either the grown children, or a caretaker depending on how health goes. Have you done this recently? Which design/build (or other) company did you use? Seems like the one we hear most about is 'new avenue', but then we've also heard they were a spin-off from an original company, who we can't seem to find. Any company recommendations? I'd assume you had 3 bids, but again we're not finding multiple companies who do this.

I understand this can be a loaded question, but approx how much did you end up spending? (We're in Berkeley). Any recommendations for 'where to start' the process?

Thanks for any recommendations, advice, warnings, etc. Hopeful backyard cottage rental unit owners

I researched and built a backyard cottaage about 6 years ago. Strongly suggest first going to the planning office to learn what regulations you'll need to pay attention to. And find someone proficient in Berkeley rental law to understand that too.

After an architect took me to the cleaners (her fee almost 40% of the total project fee) I ended up getting a tuff shed garage and tricking it out on the interior. All told, $50K ish. Depends of course on your budget and what you're looking for.

The City of Berkeley was the most painful part of the entire thing - it was an endurance event of pain, waiting, obfuscation, and delays. Insane. Utterly. Loved my cottage in the end but the whole thing took years off my life. Good luck! Do your homework

First off, don't advertise that you expect to have income from the Cottage. It is easier to get approval for an 'In-Law Unit' than for a rental, or 'Secondary Unit', and sometimes neighbors can make life difficult if they think you are renting an 'In-Law'.

I have designed some ADU's and gotten them through the permitting process - others have built them. The last one cost around $135k, in 2009. It was about 400 sq. ft. Came out really nice, used by the grandma when she's in town, who is brave enough and agile enough to utilize the loft. The person who built it has moved on to bigger things, but I team up with Springwood Builders when I can.

I know this forum is not for us to talk up our businesses, but I also have some 'advice' that can be helpful to anyone who is considering this. I think the best way to start off is to go to the Planning Dept. with a sketch of the property with the approx. locations of the main house and the proposed cottage. You might be told by the planner that you can situate the cottage far back on the lot, b/c you are already getting a use permit. Careful on this, b/c it can lead to a requirement of automatic sprinklers, an expensive proposition. I could go on, but ...

I hope this helps. . Andus B

We used a company called Summerwood - highly recommend them. Great products, incredible customer service, great 'help' department. We built in Alameda and yes, planning department was the worst part of the experience. We also worked with an architect at first - he proposed us spending over $100k for about 400sf (which was $50k over budget). We purchased the 220 sf unit for about $11,000, and finished (electricity, sheetrock, lighting, painting, furnished came in around $18,000). The great thing about summerwood is you design the until - pick where the widows and door go, etc. We built what is typically a pool house but will tuck into a corner. We lived in our studio as much as the house, perhaps more. Its a great investment. good luck

Backyard Cottage/Tiny House - have you built one?

May 2012

Hi, We're considering building a 'Backyard Cottage' or 'Tiny House' in our backyard in the Berkeley flats. We're unsure how to proceed, and want to ask some locals about the pros and cons. We're thinking 400 sf or so, to use as a rental and/or when visitors come.

I understand that Berkeley is replete with such structures, and there's the one well-known one that got a lot of press last year (the UC Berkeley professor). But, have others built them recently? If you have, who did you get to do the construction, and did you buy a plan or have one firm do the design/build? What was the total cost, and what do you rent the cottage for? Would you recommend doing it? Pluses and minuses?

Thanks for any information, advice, recommendations, cautions... Hope to add small unit

Dear Hope-to-add-small-unit, I designed an In-Law Unit recently for a client in the flats of Berkeley. It is 450 square feet and cost about $130k, not including pre-construction costs. Eric Manou built it. In-Law Units are easier to permit than rentable units, which require a use permit with a public hearing, separate utilities, etc. I hope you enjoy the process.

I recently designed a small cottage in Alamo. It was 776 square feet and construction estimates came in at around $220K. You'll want to look at the zoning requirements for your lot and confirm setback distances and height limitations. You'll also want to look at parking requirements to determine if an additional parking space will be necessary. Lastly, talk to the city about permit fees for your project. The fees required for a project like this are often greater than clients expect.

I have to say that, in order to expand space potential for our tiny Albany house, we ordered up a backyard cottage from the Shed Shop in Fremont: This was probably nine years ago, but the cost came in at under $80,000, including the concrete slab foundation we put in, and the shed is still going strong. This was a one-room thing, however, with electricity and phone line. Not a mother-in-law unit. But worth looking at for extra space. spatially challenged

We went down the architect path for a small backyard cottage and it was a nightmare that cost us $7,000 in fees with nothing at the end as our $60,000 budget became an unfinished unit estimated at $110,000. Then we found Summerwood - and spent $12,000 for a 'pool cabana' that fit perfectly in the corner of our yard. It's 220 sq feet, and when you add Sheetrock, electricity, roof, lighting it was just about $20,000. We then re-did our yard and it all looked/s amazing - and was way, way better than the 400 sq foot planned structure. We could have easily added a sink, but for a toilet would have need to trench across the yard - do-able but we decided a second bathroom in the house made more sense. Happy to tell you details of our summerwood experience - amazing! No waste (all the wood is precut) - we love the windows and doors. Our house has been on a number of garden tours and people always ask about the structure. Love our cottage

Prefab backyard bungalow/cabin/in-law?

Jan 2011

Hello, We are considering the most inexpensive way to add a small 'bungalow' / cabin / in-law apartment to our Berkeley backyard. Has anyone used one of the pre- fab 'kits' for building such? Which company did you use, and how was it? How is it holding up? Other ideas for rather inexpensively adding a live-in 'apartment' to our backyard? Any recommendations/ suggestions welcome. Thank you! Need a little room

We had an estimate from an excellent contractor who specializes in prefab in law cottages. I have seen several that this contractor made and they were beautiful little homes. His price included all cabinetry and kitchen appliances. His name is Steve Vallejos and here's his email: Steve Vallejos stevevallejos [at] I can tell you more specifically if you want to call me: 529-6328. Micky

Not sure if this would meet your needs, but definitely worth checking out -- Tuff Shed. We built one several years ago to use as a workshop. Although ours is not plumbed or heated, I think you could add those things to the basic structure. Since it's on a slab, radiant heat would be ideal. We also added skylights (which are an option) and the space gets lots of natural light from them. We don't live in ours, but we know someone who does and it seems to work for him. Once you get all your permits in place, construction is super fast. Happy with Tuff Shed