Using an ADU for Multigenerational Living in San Diego

I look at an ADU, an accessory dwelling unit, as a way to house family on land you already own. Separate entrances and windows above eye level can give each household privacy, and the space can serve a different purpose as your family changes.

Watch on YouTube

Key Takeaways

  • In my November 2025 hypothetical San Diego comparison, a 750 sq ft ADU at about $400 per sq ft came to $300,000 in construction before soft costs.
  • At our completed Bancroft ADU and Garage, the front house uses the street driveway and the rear home uses alley parking.
  • At Bancroft, we placed backyard-facing windows above eye level to keep the ADU's occupants from looking into the main home's yard.
  • I recommend deciding how close you can comfortably live to family or friends before planning more homes on your lot.

Regulations Cited

  • SDMC 141.0302
  • Gov. Code 66323
  • SDMC 113.0103
  • DSD Information Bulletin 400 (January 2026)

Checked against these sources as of November 2026.

Full Transcript

00:00BaileyHousing in California has become very expensive. So much so that the traditional model of everyone in the family owning their own separate home has unfortunately become less and less realistic. So because of these economic factors, today on the podcast, we are going to be discussing multi-generational living.

Not just as a reaction to these high costs, but as an intentional design strategy so that you can create privacy, flexibility, and long-term value on your property. So Sean, I know you've been working on several multi-generational living projects. What are you seeing with clients who are exploring these multi-generational options?

00:43Sean CanningYeah. Well good morning Bailey. Thanks for setting this up again. you used the term reaction and I think that kind of sets the stage for exactly what we're seeing here. One way to look at this is the building department, or in this case with ADUs, the state establishes the rules of the game, but then the way the strategy that you play the game is more of a function of what the market allows. So.

When ADUs became a thing about five years ago of course driven by the state, I think the intent was for people to build ADUs that would be used for rent and then people would be renting these to people outside of their family. I think that was ultimately the goal. But because of the way the market economics have shifted with construction costs being high right now, and interest rates still being high, I think the ADU now becomes the perfect solution for multi-generational living. I think the general public has picked up on this because we've seen a few more clients come in the door asking for this.

In fact, I think the first client who asked for this was about three years ago, right? About that tipping point where you started to see interest rates spike. So I think for a lot of this conversation, it might be interesting to use you as an example. at some point, Bailey, you'd probably like to get into the housing market.

I know you're in Colorado, which also has a challenging market. Maybe for the sake of this conversation, we can use you as an example if you were trying to get into a home in Southern California.

02:11BaileyOkay, so I'll be the 28-year-old, older. I think I'm actually Gen Z technically, so I'm like the oldest possible Gen Z, so that makes sense. Do you want to go deeper into that or do you wanna move on to the next question I had here?

02:27Sean CanningYeah, let's pause here for a minute. So let's just set the stage here. Let's say you wanted to get a home in San Diego or Los Angeles. I own a home here and I have a backyard. You would be trying to buy a home. The average cost for a home is a million dollars. might be lucky enough to find something around 600,000, maybe $700,000. But it doesn't get too much cheaper than that out here, to be honest with you. your generation, unless you're you know, incredibly wealthy or inherit some money or have a very, very high paying job, you're essentially priced out of the real estate market here in Southern California. here I am with a large backyard We have about 70 by 25 feet of buildable area. So it would actually be more cost effective for you to invest in a new home in my backyard. And then at the conclusion of the project, it would be the same exact situation as if we both had homes. On smaller lots, let's just do some math here. Let's say we were gonna build market rate right now for rental property, that'd be about $400 a square foot. if we were to build you something that was like a two bedroom, one and a half bath, which would be a pretty nice starter home, that'd be about 750 square feet. So you're talking about $300,000 to get in that type of home. Versus probably closer to 600 or $700,000 to buy that type of home. it's like a 50% discount if I'm willing to give up some of this land and make an accommodation for you to live here.

Now this works perfectly, not only just for family, but also for friends too.

And that was the first instance I saw of a client saying, Hey, I'm gonna have my best friends move into my lot. We're gonna build a new ADU for them. So do you see the major advantage here because of that high cost of housing,

04:16BaileyI do. Well, essentially you're getting rid of the land cost in this scenario, so that's obviously gonna have a dramatic impact. And then all you need to worry about is a construction, of course, right.

04:26Sean Canningyou may have to take out a construction loan, which you may not qualify for as a, 28-year-old, but it could be something that, you know, with my name on the loan, we could probably do something like that. So all of a sudden, what was. a solution for the housing crisis and maybe to increase rental properties becomes the perfect scenario for people in your generation who have friends or family that live in this area already and own homes to really. become your first starter home. there's probably some challenges with this. You know, what would be, could you resell the, the ADU in some scenarios now you would be able to, so you could actually, probably, on different criteria and what city and what zoning you have, is now an avenue where you could. Own the ADU and I could own the dwelling unit. And if you decided at some point you wanted to sell the ADU, you could potentially do that depending on some very like narrow criteria. But that is becoming an opportunity because the other solution, the other scenario would be probably me as property owner would own. The ADU and then you'd either have to be added to the, to the deed of my property, or you would essentially be, become just a renter, which would not really be true ownership.

05:43BaileyDefinitely, and I think it's worth just highlighting for the sake of the conversation here, how I believe. That the average age of a new home buyer at the time we're recording this. A first time home buyer is now 38 years old. So you know, going back to like the late nineties, early two thousands, they probably would've been my age, late twenties.

Now it's pushed back a decade, and I think in general the average age of a home buyer, so all home buyers is something like 56, 57. So that just kind of goes to show the age range of people actually buying homes in today's market.

But moving on to exactly how you would fit these types of multi-generational living units on a lot, can you walk us through some different scenarios in terms of how you can leverage ADUs, J ADUs, all the different housing options available to actually set it up where a family can live together, albeit in separate units.

06:37Sean CanningAnd then eventually we're gonna have to get into the conversation of privacy because I know a lot of people here, oh, my in-laws are gonna be moving here. I need privacy. before everybody tunes out thinking that they can't live on the same property as their in-laws, we're gonna get to the privacy conversation. But if you own a home in California, and that home is classified as a dwelling unit, which basically all homes are, so it would exclude a condo. But if you have a, a dwelling unit, you could build an ADU, on your property as long as you have space to do it. So this works way better if you have a backyard, it works. Less good if you have to build a second floor, although it still works, but it certainly complicates things. So any property that has a home can build an ADU and then you can do this now in certain scenarios. If it's a single family home, you could. Build an ADU detached, you couldconvert your garage to an ADU, so that would actually give you two ADUs plus the single family home. then you can also build a junior accessory unit, A-J-A-D-U. So that would actually give you four independent living. Spaces a lot that previously had a single family home it's zoned single family. if you live in a multi-family zone you have a single family home built, you could build a second dwelling unit, which may actually be the best angle here, but those are gonna be rare cases where you're in a multifamily zone and have a single family home. But if you're in that multifamily zone, you could build a second dwelling unit and then you could build two more. ADUs. So that's a way where you could, in theory, get four detached units or maybe two detached duplexes. of course, the more detached these structures are, the more privacy everybody has and everything I've mentioned to you now. Goes throughout the entire state of California. So you can do this in San Diego where I work. You could do this in Los Angeles, you do in San Francisco or Sacramento. And none of these require affordable housing. So it's all market rate housing.

08:39Baileyo

nto the privacy concerns then. So obviously no one wants to feel like they're living on top of each other, and certainly people don't want their neighbors looking through their windows. So what are some design strategies you deploy in these types of situations so that while yes, it's a tight lot with multiple people and units living on them, how can you still maintain that level of privacy people expect from a, you know, single family home?

09:04Sean CanningAnd this is everybody's concern, right? Because you know, you don't want your parents or your in-laws impeding on your private life. So a couple different ways you can do this. First, let's just phrase this again in the context of the cost of lots and. The size of lots. So the smallest lot you can buy here with the cheapest home is probably $600,000.

And this is gonna be probably like a 2000 square foot lot or less Now that's 1.2 million to buy two of those super inexpensive lots.

09:38BaileyWait, you said, so it's 600 K per lot.

09:41Sean Canning$600,000 will get you into the smallest home on the market. that home is gonna come with a hostage stamp lot, like the smallest lot you can find with no backyard. Now,

09:52Baileyabout you? What about utilities you think? Would that include utilities?

09:56Sean Canningif you, no, that doesn't include utilities, but if you buy the home that's there, there's already utility hookups, but. account for you to, you know, pay the utilities every month. And we have like the highest electric per kilowatt hour in the United States right now in San Diego. Doesn't matter how you play this, like you're gonna be paying utilities. So it's almost like it's not part of the equation, but, okay, so here's the setup. you buy this 600 square foot lot and you buy this 600 square foot lot. You're now a 1.2 million between the two of us. I have my own lot. You have your own lot. But if you have somebody who's a friend or family who's, you know, close enough and willing to do this, the lot that I've purchased here, I bought it in like 2022. I only paid $400,000 for this lot, and it's got all that space in the backyard. So now instead of you buying the $600,000 tiny lot, you're gonna invest $300,000 into construction and we're gonna have the same exact scenario. So the price that I paid for the lot. the price you're gonna pay for construction. We're up to $700,000 we're not including like soft costs, but basically $700,000 instead of the $1.2 million. Lot situation. So bringing us back to privacy, so you're gonna say. Well, is it really private if we're building another unit for you in my backyard? Like can we still maintain privacy? And the whole point of that explanation is, well, it's the same exact scenario as if we had those two smaller lots. We're just doing it at a much more cost effective way to do it. Okay, so then getting a little bit more into the weeds of privacy. First thing I would recommend is you want to detach. ADU or the dwelling unit, whenever possible, if you can have two detached homes, it's far more private than if you share a wall. If the lot is big enough, there's an opportunity to do this. Now if you build an ADU, you're gonna get basically a separate electric bill. So you would pay your own electric, you'd get a separate gas bill. If you have gas, because it's all tied into San Diego Gas and electric, water bill would be shared.

So we'd split it at the end of the month, or you'd pay a flat fee or something like that. And there's a new trash fee in the city of San Diego, so we'd each pay our own trash fee. The trash fee appears on the property tax, so I'd basically have to bill you for what I'm paying on the property tax. Now. If you wanted to add another family member, so you're my cousin, but let's say my parents needed a spot to live, so we're gonna find another way to bring my parents here. Or sometimes maybe you have a, you know, a single parent and a single parent can be more difficult for them to make everything work financially.

So that's a fairly common scenario. now I could build a second day to you 'cause I'm. I'm in a multifamily zone. I can build a second ADU and have that family member live in that second ADU. If my lot is big enough, I can do this in three detached units and that would be the most private. If another way to do this would be if I had a single family zoned lot, I can build A-J-A-D-U, which has to be attached to the dwelling unit. And if I do that, then. My parents could live in part of my house, which would basically become ADUplex. On paper it'd be a single 'cause. A doesn't count as another unit, would function like ADUplex. And that would be less privacy than I would really want. Butthere's a clear avenue to have three different people here. And now, if I had a garage, which I don't, but if I did have a garage, I could convert the garage. And then if I had a deadbeat brother or something that needed a spot to live well, he could live in the garage. And now we have four people that designed correctly, all could live much cheaper than if they all bought their own homes or rented. ButIt also provides an avenue for people to live in the same lot. lemme just dive a little deeper into privacy. So the key thing you wanna consider is access. So you're going to have people accessing their units from where they park. You're gonna have people accessing their units from the sidewalk, because if you bring a guest over, they're coming from the sidewalk. some people have a driveway in the front, some people have an alley in the back. If you're lucky enough, you have both. And that really creates the best opportunity here. But you're always gonna have access from the sidewalk because if you have a guest come by, they're gonna come from the sidewalk. you have a solicitor, they're coming from the sidewalk. So all the units need access from the sidewalk, and then if you have a driveway, the front unit gets access from the driveway. If you have an alley like I do, the people who park in the alley would have access from the alley. So if you have a unit in the back of the property. They access from the alley parking, but they also need a pathway from the street, from the sidewalk where their guests would access. So the shortest distance between two points is a straight line. So ideally you wanna provide one entire side yard you can get cross access for the alley if you have it, and also from the sidewalk. That becomes the most efficient way to have this privacy. And then once you establish that path of access, you don't want your windows facing that path of access because you don't wanna be chilling in your living room. And then all of a sudden, you know, my brother comes home and. He's walking right past the window in your living room.

That would be like an awkward scenario, there's certainly solutions for this. If you did a two story, ADU would be a non consideration. You could do frosted windows, you could do clear story windows, which are above eye line, and then you'd never notice somebody was walking. So then it comes down to kind of like the smaller details of how you design these things. Once you Have established that path of access, so there's lots of strategies to maintain privacy, while increasing density on a property.

15:41BaileyTotally. That makes sense. And we definitely don't wanna recreate the whole living with your parents living situation just in reverse opposite stages of life. So definitely that is one reason why privacy would of course be very important. We've been talking a lot of theory and abstractly, I feel like so far.

Do you have maybe an example from the portfolio of the studio we can look at to illustrate what this would mean for. Prospective clients considering this type of a project?

Okay, so this is a project we recently finished. This is called the Bancroft, ADU and Garage. We did some cool things on this project, since it's one of our newer finished projects. I thought this would be a good one to show you some examples. So these are some photos of the project.

Let me just orientate you. here's an existing dwelling unit. Lemme see if we have a photo. Okay, so. Do we have a street photo? Okay, so here's the existing home. It's kind of a quasi historic craftsman home. And behind that we built this ADU. So I wanna point out a couple things here. There is a driveway in the front, which you could see in this rendering. So the person who is my client who lives in the front house, they access their property through the driveway in the front, and the front door is like kind of right over here. Let me see if I have a better image of this. So here's the driveway that comes from the street, and then here's their home, and they'll enter through the front. And the person who lives here also has access to this backyard. Now here's the new ADU we built, and the new ADU enters the home from here and they have alley access here. So we've provided one parallel parking space here. So they'll park here and enter their home here while the property owner parks here and enters their home at the front. in this scenario. We actually don't need really any of that cross lot access. So we do have a clear pathway here, but they're so close to the corner. This is one of the rare exceptions where any guests that this tenant has will come from the corner and then down the alley and they'll enter here. by creating two distinctly separate formal entries, which is where you. Enter the home as a guest and informal entries, which is where you park and then enter the home as a homeowner. no overlap here. They have complete privacy. Now. You may say, well, what about this backyard? Isn't this ADU looking down at the backyard, creating less privacy for the homeowner in the backyard? Well, that was one of the concerns we took into consideration as we went through the design phase. So I wanna see if I have a good image here, which shows you how much privacy they would have in the backyard. So is maybe the best photo I have to show this. But you see we've lifted the windows here above eye line. the backyard is kind of down here, and the tenants in this unit are not tall enough. They're just like, they're standard height, but you'd have to be like seven feet tall to get. Your eyes up here and then see down into the backyard. So by lifting the windows in the area where we do not want the view, we're able to establish that privacy. These windows look towards the alley, so there's plenty of, plenty of privacy in that direction. And then here we have a balcony, which is on the front of the house you can kind of see here. So they do have a view towards the driveway and this is just an AI. Turf. The driveway was not completed when the photos were taken, but there is a driveway here. So the only like conflict of privacy here is if the tenants up here are looking down at the driveway, which is really kind of a non-issue. also a garage here, so the homeowner has access to the garage and when they enter the garage, they exit. towards their backyard, and then they can enter through, the back of their house right over here back through that like exterior space. We even took this one step further and on the ground floor of this two story, ADU, there's a second bedroom, and that bedroom was designed to be potentially rented by the tenants. Also have the flexibility to be used as a home office space by the homeowner. So we've kind of set up this floor plan where that one room on the ground floor could be used either way. So I guess that's a good example. This is the, this is the window of that office space. And again, it's above eye level.

So even if you're a tenant renting that office space, you do not have a line of sight into the backyard. So maybe that's a good example of how to establish privacy. Here's that parking space, through having non conflicting points of access for the home.

20:18BaileyI agree. I think that's a very solid example.

Now, obviously people might be hesitant to get into this sort of a situation out of fear that they might be locked into it forever. So they're always gonna have their in-laws on their lot. For example, how can you design these multi-generational units so that in the short to medium term, of course, you can have different family members and maybe even close friends live in the lot.

But then long term, in order to future-proof the investment, you could set it up so that these separate structures could be used in a variety of different ways.

20:53Sean Canningthat's kind of the beauty of the use of the ADU and I, I think a lot of people don't realize this because they think about it in kind of like a, a black and white scenario, but. Let's say I had my parents move into the ADU my backyard because you know, they didn't save for retirement, so now they need a place to live.

So we build the ADU. My parents move in there now, later on in life, maybe I have kids. My parents are no longer in the ADU and now. Kids need to go to college, they're gonna stay local. But you know, that dormitory is very expensive. So now my kids can move into this ADU let's say, you know, my kids were to, go to an out-of-state school and commuting was not an option.

Well, now that ADU can become a rental unit and I can rent it and monetize it. So right there, I've already had three different. Huge uses for that. ADU. Then let's say now I'm retired the the ADU is smaller than my house and I want to downsize my lifestyle. Well now I can move into the ADU and I could rent the home because my house would be set up larger and I could command more rent. So there's another use. And let's say my retirement plan kicks in and I have lots of extra income. Well. Now I can keep both for my use and the ADU could become a guest house for when guests come in and they could start to use that and stay over so they don't have to stay inside my house. maybe partially retired and that ADU can now become a home office or maybe a home gym or maybe a home studio because I wanna invest some time into my guitar playing. So I think I've just rattled off like. Over a half dozen key uses for an ADU where I think a lotof people think the ADU is really just for one thing.

22:42BaileyYeah, there's multiple ways to set it up.

One quick thing I think we should address though, what exactly are the current regulations in regards to Airbnb style vacation rentals? I believe it's pretty regulated. So just in case someone is thinking about having one of these units being Airbnb, what's the feasibility of that right now?

23:02Sean CanningSo you

23:02BaileySo you can't.

23:03Sean Canningfor short term. Which is I think under 30 days, or 30 days or less, one of the other, so that's considered short-term rental. They're not available for short-term rental unless you get an Airbnb license. the way the city set up the Airbnb license, they said there was gonna be a maximum cap of Airbnbs, which was gonna be 1% of housing, and the Airbnbs were gonna pay fees. And these Airbnb licenses are stilleasy to get in most communities because the city overestimated the amount of people who would be Airbnb, their units. There was just another, policy that ran past city council where they were gonna charge an additional, $1,000 per bedroom per ADU, to increase more fees on ADUs to supplement the difference of the amount of Airbnbs that are actually rented versus the ones that the city expected to be rented.

And I think that was shot down. would've basically put a lot of Airbnbs outta business. You can rent your ADU. Out as a midterm rental. So that works good for a nanny. and actually that's another great use for an Airbnb. You can put a nanny in there. I have another client who wants to put a caregiver in there because they're getting to that point of life where you. They're gonna need home care so that the caregiver can live right on site in the Airbnb. But this would be a good midterm rental or long-term rental solution. But it probably doesn't make sense as a short-term Airbnb rental solution with the current setup that the city has established for fees for short term rentals.

24:30BaileyYeah, there. It sounds like you're trying to make it as difficult as possible to have an Airbnb.

24:34Sean CanningYeah.

24:35BaileyLast two questions here. First, is there any common mistakes or pitfalls you see clients getting in as they start to take on these multi-generational living type development projects? Is there anything, any common mistake you think they should be aware of to avoid replicating?

That's a good question. Yeah, there's probably a lot of things that I would do as an architect that I noticed that some of my clients are less concerned about. And you know, I always wonder how these things affect them after the home is already built. So if you're going to build ADUplex structure. to support your family or your friends. There are minimum requirements for fire rating, which is, pretty simple to achieve. You need a one hour fire rating. there's also minimum sound transmission class and impact isolation class levels. So if I was to build ADUplex where one unit was over the other unit, that floor has to meet certain sound requirements so that if I. Drop something on the floor. You don't hear it below in the apartment. Like you live in an apartment complex right now, right?

I do, but I'm on the top floor, so that's helpful for soundproofing, you know?

25:43Sean CanningDo you know the tenants below you?

25:45BaileyNo, I don't really hear much, honestly, fortunately.

25:48Sean Canningsound U the sound usually goes the other way because if you have on like hard sold shoes or if you have a friend over that has high heels on, that sound is usually transmitting. and also we hear a lot of, like, the tenant above us has not, not above me, but my tenant, my clients tell me the tenant above them has a dog, you know, and the dog is running across.

They get Zoomies in the apartment, they run across and you hear that. Or they have kids and the kids are running around and

26:16BaileyYeah.

26:17Sean Canningtransmits down.

26:18BaileyNo, I had, my one neighbor had like a crying baby, which was a disaster as you could imagine. The high pitched just goes right through the walls. But no, I was, honestly, I probably make the most noise out of anyone. You'll find this funny. Yesterday I was blasting in the middle of the afternoon, the Guns N Roses song right next door to hell.

And I thought it was pretty ironic. But back to the soundproofing, what are some things, or just in general, the common pitfalls people need to know about?

26:45Sean CanningYeah, so the code establishes minimum sound transmission but you can always go beyond that and oftentimes it doesn't take too much more money to go beyond that. if you choose not to do this when you're building the home, it's almost impossible to like retrofit this later. One thing I would say is you wanna make sure that your floor, if you're on top of another unit, or your wall, if you're adjacent like horizontally to another unit, are built at probably a higher level than the code would allow.

'cause the code establishes a minimum requirement. for sound transmission. And then there's another requirement for impact isolation kicks in on a floor where you're above another unit. So that covers like, you know, your high heels, your dog, your kids, if you ever drop like some silverware on the floor that. Tenant below you is hearing that. impact isolation is actually harder to achieve, but same thing as sound transmission, you can go above and beyond. I would say that would be one thing that I would certainly consider. And the other thing, you know, this is something that comes up quite a bit. I always recommend a detached A to U whenever possible because just staying on the same subject of sound transmission. If you have six feet between your structures, that's great sound isolation. So I know I have some clients that are saying, Hey, I want it attached my recommendation. As long as space allows, always do this detached.

28:07BaileyYeah, I agree with that. But what would be the key pricing considerations people would need to think about? So if possible, imagine same structure attached detached. What's the price difference?

28:18Sean CanningDetached actually is potentially less expensive. There's less issues once you start working around an existing home and like doing a remodel or an addition. As soon as you open up the wall of, or the walls or the ceiling or the floor, you're gonna find issues. And then you have to marry a new construction standard with whatever is there.

So you're maybe working with like a home that was built in the twenties. are gonna just be completely different. So every time you're gonna do an attached structure, you open yourself up to the risk of what is actually happening in that. existing structure. And a lot of times you may not want to know what, what is inside those walls. So I would say a detached structure, even though you're gonna pay for probably one extra wall because you're not sharing the wall, I think the detached structure would be probably more cost effective. And I think a contractor would be more comfortable giving you a quote for something that's detached rather than giving you a quote for something that's attached.

In fact, we work with contractors that will only do detached and they don't wanna do attached structures. But now to your point. One common attached structure is the garage conversion. have an attached garage, this is usually your lowest price point to get a unit built for. As an ADU or A-J-A-D-U, if you can convert that garage, you already got, you know, four walls and a roof and a floor. So that's your lowest price point. So in that scenario, I would probably invest extra money into sound soundproofing that garage.

29:48BaileyYeah, I'd say the soundproofing is the one thing you would wanna splurge on because it's this type of thing where if you don't, you're gonna probably regret it later. So, last question here.

Say someone is interested in this type of a project. it doesn't even need to be multi-generational necessarily.

It could just be that they wanna start building multiple units on their lot for all the benefits we've discussed. What would they need to research, would you say? Or just think about before setting up a consultation with an architect such as yourself.

30:18Sean CanningWell, I think the first thing they should do is really think about this at a high level. You know, can you live, if you had the privacy, but how close can you live to your family and friends, I've had some good friends that I would not probably be able to live that close to. I have some family members that I probably would not be able to live that close to. So you have to really consider if this is the right solution for you. You may be helping out a family or friend, but you also could be seriously compromising your own lifestyle, so benefit to them. Possible downscaling of your lifestyle for you.

So you have to make sure you're comfortable with that. In terms of like planning for. The whole project. I think that's something that I can help people with. So the first thing I would do is reach out to an architect and go through all of the considerations that come with something like this. Like, let me give you an example. I do consultations for potential clients all the time. One of the first things that I like to look at is can the existing utilities support the new. project, whether that's an ADUJ, ADU two ADUs, can the existing utilities support that? Most of the time they can, but if you're talking about two ADUs, if you're talking about, you know, adding three bathrooms, four bathrooms, some point your existing water meter is not gonna be able to support this, and you're gonna end up with about a $50,000 utility upgrade. You need to know about these things upfront, especially if you're on a limited budget. You also want to get a good understanding of all the soft costs, so you want know generally what fees you're gonna pay and how much those fees are. So, I was to tell you, okay, the building permit's gonna cost $15,000 or maybe you're calling the DSD and they're saying, yeah, it's gonna be about $15,000. and they kind of ballpark their permits on their website. So you may be going into this thing thinking you're gonna pay $15,000 for a permit, but you don't know you're gonna pay $4,800 for a sewer and water fee and you don't know you're gonna pay $5 and 17 cents for school fees. Et cetera, et cetera.

It's very hard to kind of like itemize all of these fees. then, you know, to make it even more difficult, the city has switched to this dynamic pricing, which we're still trying to figure out how this is all working and you're gonna pay these fees at the time you get the permit. So all of the fees will be higher by the time you're ready to permit. the city increased their fees four times last year, so they're going to continue to increase their fees, if you start the project now and you end up issuing the permit a year from now. a good chance they will be increased four times by the time you're ready to go. So you also have to have like a little bit of a contingency. Okay. Just to answer your question, reach out to an architect like myself. I'm always available for consultations. We'll go through the procedures. I can give you a ballpark estimate of my fees and the engineer's fees that are gonna be. Generally we need a structural engineer. Sometimes we need a civil engineer. Sometimes we need an MEP engineer. get a good understanding of the real prices that you're gonna pay. Get a good understanding of how much the construction's gonna cost. the timeframes and what that's gonna mean. You know, if I have to move outta my house so we can build a second story addition for you. There's a huge cost that comes with my living condition for that period of the project. and then lastly, I would say understand the process that you're.

Buying as part of those fees from the architects. So in our process we're gonna have three to four meetings generally, depending on, you know, what's right for the project, and that's what's included in the fixed fees that we're offering. If you do a discretionary permit, those are gonna be additional fees.

If you have an HOA, that's probably gonna result in additional fees. So your first step is really to reach out to an architect and have this discussion.

33:59BaileyYeah, it is not something you can wing, let's put it that way for sure. It's not something you can improvise your way through.

34:05Sean CanningNo, if you were to live in a very low cost area where permits were easy to achieve and construction was reasonable, you're handy, like you could probably wing this and do it as a owner builder, and maybe even do a little bit of the work yourself and reduce the fees. But in California it's, it's like the big leagues here. It's not easy to get a permit. Construction cost is expensive, labor's expensive. Material is expensive. Land is expensive. Basically everything's expensive. So you really wanna have your ducks in a row.

34:33BaileyTotally, and based on everything you mentioned there, we've made videos on that in the past. So I will link as many helpful resources as I can if people want to go a bit deeper into the different subtopics. That we mentioned here today. 'cause that would be a great starting point for sure, if they're researching a potential project.

But anyway, Sean, whether they're looking to schedule a consultation in hopes of developing a full scale, full scope type of a project, or maybe they just need a couple hours of assistance and help in the research phase, what are some different ways they can get in touch with you and your studio directly?

35:07Sean CanningWell go to 10 70 architecture.com. There's a section there where you can book an appointment for a consultation if you already own a property. I also have appointments for on demand. Architectural consultations. If you need a little bit more advice on which property to buy or where to consider buying, you could also check out our portfolio right on the website, but you can also go to our Instagram, which is at 1 0 7 0 architecture and make sure you like our portfolio before you reach out to us, because we're generally designing projects in that similar style. And I'd be happy to help you with your project if you're considering doing anything like this.

Can an ADU Make Multigenerational Living More Affordable in San Diego?

Yes. As of November 2025, my hypothetical San Diego comparison put a 750 sq ft, two-bedroom ADU, an accessory dwelling unit, at $300,000 in construction. That assumes about $400 per sq ft on land a friend or family member already owns, with soft costs, expenses outside construction, still to add.

That’s where the opportunity comes from: someone already has a backyard and is willing to share it. You’re putting money into another place to live on that property.

Part of my comparisonMy example
Construction rateAbout $400 per sq ft
Starter-home layout750 sq ft, two bedrooms, one and a half bathrooms
Construction total$300,000
Buying a separate home$600,000 to $700,000 if you’re lucky

The construction total comes from multiplying 750 sq ft by about $400 per sq ft. I’d still budget for permit fees and engineering, along with any utility work the project needs.

How Many Separate Living Spaces Could Fit on My San Diego Property?

Four living spaces may fit on an eligible San Diego single-family lot: the existing house, a detached ADU, an existing garage converted into an ADU, and a JADU, a junior accessory dwelling unit of up to 500 square feet inside the main home. State law requires cities to allow that combination, and I check the property before designing for it.

San Diego’s ADU bulletin lists the same combination. Because the JADU sits inside the main home, I’d weigh that loss of separation against the convenience of housing another family member there.

Space for separate buildings is part of the decision. A backyard layout gives me more freedom to separate households than a second-floor addition above the main home.

How Do I Keep an ADU Private From the Main House?

I start ADU privacy with the routes people take from the street and their parking spaces to each front door. On a lot with an alley, that can mean a side-yard path connecting the sidewalk to the rear home. I keep living-room windows away from that route.

The awkward moment is simple: you’re sitting in your living room and someone walks right past your window. I want to solve that while we’re laying out the homes.

A resident may arrive from an alley parking space while a guest arrives from the sidewalk. I work through both trips before placing the windows. Where a window needs to face a path, frosted glass or a window above eye level can protect the room’s privacy.

How Did You Give the Bancroft ADU Its Own Privacy?

At our completed Bancroft ADU and Garage project, we separated access to the front house and the rear ADU. The homeowner uses the street driveway, while the ADU has an alley parking space and its own entry. We raised windows above eye level where they face the main home’s backyard.

The property’s location near a corner also helps guests reach the rear unit through the alley. We could use that corner route for guests as well as the alley parking route for residents.

The upstairs balcony overlooks the driveway. The windows facing the backyard sit high enough to keep occupants from looking down into the homeowner’s outdoor space.

We also designed a ground-floor second bedroom that could serve the ADU’s tenants or become an office for the homeowner. That room’s window is above eye level too, so the flexible use preserves the backyard privacy.

Should I Attach an ADU to My House or Build It Separately?

I generally recommend a detached ADU when the lot has room, because physical separation helps with sound. If homes share a wall or a floor, I’d put extra attention into sound isolation during construction. I want the dog getting the zoomies upstairs to stay an upstairs problem.

Sound coming through a shared wall and footsteps coming through a ceiling are different problems, and I’d address both during design, because improving those walls and floors later can be extremely difficult.

For that same November 2025 construction comparison, a detached new build was potentially more cost effective than attaching to an older house. Opening existing walls can uncover problems, and the new work has to connect to what’s already there.

A garage conversion was the possible lower-cost exception: its walls, roof and floor were already there. If I were converting an attached garage into living space, I’d put extra attention into sound isolation at the shared wall.

Can My ADU Serve Different Family Members Over Time?

A San Diego ADU can serve different people as a household changes. In a hypothetical family arrangement, my parents could live there first, followed by children attending a local college. If those children studied elsewhere, I could consider a longer-term tenant and keep the home useful.

If I eventually wanted to downsize, I could move into the smaller ADU and consider renting the larger house. I could also keep both spaces for my own use.

The ADU could become a guest house, a home office or a studio where I spend more time playing guitar. I want to think past the first occupant while we’re designing, so the next stage of life has a place in the plan.

What Should I Work Out Before Planning a Multigenerational ADU in San Diego?

I’d start a San Diego multigenerational project with an honest question: can you comfortably live this close to these particular people? I have good friends and family members I probably couldn’t share a lot with. Privacy helps, but the arrangement still has to suit your life.

Then I’d check whether the existing utilities can support the additional homes and bathrooms. A permit allowance alone leaves other project costs to work through, including engineering and any water or sewer work.

The construction plan also affects where you’ll live. If a second-floor addition means moving out, I’d account for the cost of living elsewhere during the work.

Trace the route from your sidewalk and parking area to the proposed home, and talk with the people who might live there about how much separation you each need. If you’d like help planning a home for family on your lot, we offer a complimentary consultation.

Questions You Might Still Have

Can Friends Share the Lot Instead of Family?

Yes. One of my first clients pursuing this wanted a new ADU for best friends. The personal question is whether you're comfortable sharing a lot with those particular people.

How Should We Think About Ownership If a Relative Pays to Build?

I'd settle the ownership question before committing construction money. My scenario leaves several possibilities to resolve: the homeowner owning the ADU, another person joining the property deed, or a condominium split that lets the ADU sell separately. San Diego's code has allowed that split since August 22, 2025, outside the Coastal Overlay Zone, the city's mapped coastal area, subject to conditions that include a condominium subdivision and written consent from each lienholder, such as a mortgage lender. I wouldn't promise separate ownership or resale without checking the specific property.

Can an ADU House a Caregiver?

That's one use a client wants to plan for. The goal is to have a caregiver living on the property as the client begins to need home care.

Would You Build Around Airbnb Income?

No. San Diego's municipal code bars renting an ADU for less than 31 consecutive days, so I plan around family or a longer-term tenant instead of vacation-rental income.

Should I Look at Your Portfolio Before Booking a Consultation?

Yes. We generally design projects in a similar style to the work in our portfolio. I want you to like that work before we discuss your project.

Episode
14
Published
Updated
Length
36 min

Got a project you'd like to discuss?

  • Talk through your vision for your project with an experienced architect
  • Receive honest guidance on feasibility, if the project is possible or if it makes sense
  • Understand general project costs and timelines so you can make an informed, responsible decision
  • Walk away with a clear picture of the process an architect will use to bring your project from where it is today to a reality
Instagram @1070architecture
Studio San Diego, California