00:00Baileyif you've looked into building an ADU in San Diego, you've probably noticed that the rules. Don't always make sense. That's because the state has its own ADU law and the city has its own code and they don't always match. In fact, sometimes they actually contradict each other. So today we're gonna be going side by side to hopefully clear up the confusion.
Sean, to kick us off, can you give us a high level overview on the key differences between the city of San Diego Code and the state ADU law before we dive into some more specific development scenarios?
00:36Sean CanningOkay, no problem Billy. So let me just lay some groundwork first. ADUs are a state initiative. it didn't like originate at the local level of San Diego, although we did have something called companion units before ADUs were a thing in 2020, but basically the state makes the rules. The city needs to adopt those same exact rules and they cannot like minimize what the state requirements are. cities. Each have the ability to expand upon the ADU regulations, and in some cases they have done that. And City of San Diego is a fairly good example of that. So, to kick off this conversation, I wanna ask you a question. The question is, how many multiple dwelling units can you fit in a multiple dwelling unit structure?
01:25BaileyWell, I'm not gonna be able to give you a good answer on this. My guess would be two though.
01:31Sean CanningI mean, you'd have to, if you had a a, a 10 unit, multiple dwelling unit structure, how many multiple dwelling units are in that structure?
01:43BaileyIn multiple dwelling, I don't know, 20 perhaps. My initial thought was two duplexes. That's where I got the two from.
01:51Sean CanningSo. This question is impossible to answer, and that's the whole point of this podcast, the way the city has written their municipal code. It is impossible to come to a conclusion on what you can build in certain circumstances. So let me share my screen and then we'll dive into the city's written code. We'll compare it with the state's written code, and then we'll come to some consensus about what you can actually build regardless of how clear the city of San Diego's municipal code is.
Got it. Would you say at a high level, this is intentionally done to be confusion, or is it more just incompetence as per usual? Well this is a very poorly written code and it's a, this should never have made it into the municipal code the way it's written right now. So I don't want to chalk up incompetence to this, but I also don't think it was intentionally done. I think it's just really bad writing. and then whoever's proofreading this before it gets published basically was on vacation.
So, okay. Can you see my.
02:59BaileyYeah. So what are we looking at between the left hand and the right hand side?
03:04Sean CanningThe left hand side is the state ADU regulations, and the right hand side is the most updated city of San Diego regulations. let's jump into this. It starts off kind of straightforward, but by the time we get down here to subsection three B, you're gonna see exactly what I'm talking about. Okay? So right off the bat, the first question, what can you build if you have an existing single dwelling unit? So over here, we'll start with the city regulations. So it says, on a premises with an existing. Or proposed. And these two terms are very important to understand this. let's say you have an existing single dwelling unit. the way, before I go any further here, I just wanna stop and make one more important point here. Previously, we would have to dive into the zoning regulations to determine what you can build. You still have to do that a little bit, in terms of ADU development, 99% of your answers can be determined by what is existing on the property. So basically, this makes it very convenient for real estate agents and I just gave a pretty in depth presentation to a group of real estate agents to explain this. And it also makes it very accessible to homeowners, with the exception of the. Written language here. So, okay, back to this. On a premises with an existing or proposed single dwelling unit, the following is permitted and then you have subsection A here. we can do one ADU, that is with an existing or proposed single dwelling unit or within an existing accessory structure. And then they give some some minor footnotes here, which we don't have to get into right now. that's option one. And then we can combine this with option two here, which is one attached or detached, ADU. So, so far, I think this is fairly clear. If you have an existing home or if you have a vacant lot and you're proposing to build an existing home, you could essentially get two ADUs. One would have to be what they call here within the proposed single dwelling unit. Or if you have an existing dwelling unit, you can split that in half, essentially make half an ADU, half a dwelling unit, or if you have an existing garage or accessory structure, that could become an ADU. And then in addition to that, we could also do one attached or detached. Now let's compare that with the first section here of the state code and the second section of the state code. So it says, one ADU per lot is permitted within the converted space of a proposed or existing. Dwelling or accessory structure.
And this type of ADU must have exterior access and setbacks, et cetera, et cetera. and but then also it says ADUs converted from an accessory structure are eligible for 150 square foot edition. So that's the same thing that it's saying here. And then it goes into J adu. Here we're gonna ignore J ADUs for the purpose of podcast.
And then, so this section here, number one, almost directly corresponds with section one over here of the city regulations. So, so far we're right on course now, number two here, single family detached ADUs. So it says one detached new construction, ADU that does not exceed four foot. Side and rear yard setbacks is permitted on a lots with an existing or proposed single family dwelling unit. And that basically corresponds with B here, although in the city of San Diego, they're allowing it to be attached. And then in addition to that some of these setbacks that are listed here do not always apply in the city of San Diego.
So let's jump over to the diagrams here. So in these diagrams, I'm going to use to explain this. Anything that's white is an existing dwelling unit, and anything that's charcoal gray is an existing garage or accessory structure. let's say you're in this scenario here. You have an existing dwelling unit and you have an existing garage. Well, here's a couple options of what you can do. We know we can build one attached or detached dwelling unit. Sorry, ADU. So that's what we could build here. And in this context, this would be considered a detached because it's detached from the dwelling unit. But we also could attach this to the dwelling unit here, and then we can leave the garage. So that's certainly an option for you. Another option would be you could convert the garage.
So here was our existing garage. our garage conversion to an ADU, and then we still have that other ADU on the table so we can get the two ADUs on a lot that has an existing or proposed single dwelling unit. Now, it doesn't matter if it's a multifamily zone or single family zone, these are your options. Okay? Here's another scenario. And I just want to use this to kind of explain some of the challenges that come up with the permitting process and how that kind of conflicts with what you're allowed to do here. So in this scenario, you have an existing single family dwelling unit. Doesn't matter what zone it is, but there's no garage or accessory structure on this lot. So one option would be you could just build a detached. ADU and leave the existing single family dwelling unit. And that's totally cool. Like I mentioned earlier, you could also just attach this over here, and that is permitted in the city of San Diego. Now, what you could also do is because there's no garage structure, we're allowed to build the ADU. Quote, unquote, within the dwelling unit. So existing dwelling unit, which we can recall from back here. And now we can split that dwelling unit in half without adding any square footage. And now we have half dwelling unit, half ADU, essentially ADUplex. Technically, we're also allowed to add an additional 150 square feet for ingress into this structure if we wanted to.
But that's not really, we don't have to get into that level of detail here. So you're allowed to convert the dwelling unit into half ADU or a third ADU, whatever makes sense. And then you can still build that detached ADU. here's another scenario. You start with the existing dwelling unit over here. We now propose we build one detached, ADU, which is this pink mass here. And in the same permit we're also gonna propose to build a garage, which is this orange mass. after the project is complete, you sign final, you get final inspection signed off. We could now come and that. Garage into another ADU and that's how we go from one existing single family dwelling unit to two ADUs. by the end of the project it just requires two permits.
Okay, so here's where it's gonna get a little complicated. So here in the city ADU regulations, we now are going to. We're now going to start with a premises with a proposed multiple dwelling unit structure. So it says, the maximum number of ADUs on a premises with a proposed multiple dwelling unit structure shall not exceed two detached ADUs. And now we can go over here and let's take a look at how this compares to the state regulations. ADUs may be created within the portions of existing multifamily structures that are not used as livable space. Local agencies shall allow at least one ADU within an existing multiple family dwelling unit up to 25% of the existing.
Okay, so I'm just gonna cut to the chase here. Subsection three in the ADU code is actually referring to subsection three A in the local code. And subsection four in the state code is a little bit of subsection two in the city code and subsection B. Three B in the local San Diego code. Okay, so let's just kind of dive into this and out what it says.
So first we'll go through this, we'll go through the city code again. Okay. So if you're proposing a multiple dwelling unit structure, which means two dwelling units in a single structure. You could then build two detached ADUs. So a nutshell, that's this scenario here. Now here you would be proposing to two dwelling units.
So actually let me paint these a different color to make that super clear. these are being proposed. And we could basically propose this and then on the same permit, we could propose an additional ADU, or we could propose two ADUs. Basically, to boil this down, you can match the number of dwelling units with ADUs, and you're gonna see in the next section how we can do this up to eight Aus. So proposing two dwelling units. You can also get up to two ADUs. That's pretty simple. Here's where it kind of all falls apart, this section here. Okay, so on a premises with an existing multiple dwelling unit structure. Now this is a quintessential difference from proposed to existing, so. You could do this with a second permit, you could propose a multiple dwelling unit structure and then with a second permit.
Now you have an existing multiple dwelling unit structure, but you gotta jump through a lot of hoops for that. So let's just read through what this says on a premises with an existing multiple dwelling unit structure. The following applies and we have two options. The first one I think is less important than the second, so I'm just gonna skip here. A maximum number, a maximum of eight detached ADUs may be permitted on a premises, provided that the number of detached ADUs shall not exceed the number of existing multiple dwelling units in the multiple dwelling unit structure. This is the most poorly written section in the entire municipal code in the city of San Diego because this is that riddle that we started. The conversation with, there's no way to determine how many ADUs you can build in this context without going back to the state regulations so you can really understand what they meant by this. let's read this section here to two detached ADUs are allowed on a lot that has a proposed multiple dwelling U multiple dwelling. Multifamily dwelling. Okay, so that was the first section we talked about number two, but then it says, or up to eight, detached ADUs are allowed on a lot with an existing multifamily dwelling. Not to exceed the number of existing units on the lot. So you see here, they use number of existing units and if the city changed their terminology here, it would make sense.
So it should really be be updated so people can understand what this means.
So here's what this means in a nutshell. If you were to have. An existing multiple dwelling unit structure, which has in this scenario, four units, you can kind of see here how I'm trying to represent four units. That's an existing condition. Well, now we can build four ADUs. And you can do this up to eight Aus. So if this was an plex, you could, if you had the space for it, you could build eight detached ADUs. What another thing that should be updated is when it says detached, it should be made clear that this means detached from the. Multiple dwelling unit structure, but it does not necessarily mean detached from other ADUs. That's a very important clarification that should be really made here. if we had, if this was eight, we'd be able to build eight. If this was 10, we'd still only be able to build eight a Ds. Okay, now let's just dive into the last section of this, which is kind of this like little quirk. here it says, on a premises with an existing multiple dwelling unit structure, following applies. The maximum number of ADUs that may be permitted within the existing non livable space of an existing multiple dwelling unit structure shall not exceed 25% of the total number of multiple dwelling units in the structure then et cetera, et cetera. But the, it never drops below one.
So th this scenario here, we have a fourplex, existing existing garage. You can divide the four by so you get one, and we could convert that garage into one ADU. the scenario where this was, let's say, an eight-plex, could divide that by 25% and we can convert this existing garage into two ADUs. So. extremely complicated the way this is written and the state reg, the state ADU regulations kind of clarifies it a little bit. But is this making sense so far, Billy?
16:31BaileyIt is a little complex. I mean, for people who are not as familiar with the ADU code as you are, of course. How would you just like, quickly summarize the issues that you've just laid out?
16:43Sean CanningOkay, well it's the obligation of the city to tell us what we can build and if the city's service department is, as busy as they make it out to be. Providing this clarification would help them be less busy because I'm sure they're fielding a million questions right now about what you can build because how unclear this code is written and I think the average person doesn't understand you can defer to the state regulations and the city cannot. Say you can't build those because the state regulations are basically gospel. So if you have an existing single family home, you could easily build one attached or detached ADU if you have. An existing or proposed single family home or like, let's say you bought a vacant lot and you're proposing single family home.
Well, you can do the same thing. you can build that first dwelling unit and you can attach an ADU to it. You could also build that first dwelling unit and build a detached ADU. So any single family residential zone lot you can automatically, easily get to if you have an existing. A dwelling unit an existing accessory structure, which could be a garage or it could be a mechanical space or something like that. you're able to convert those existing spaces into ADU spaces, don't forget about the loophole that you could always permit these accessory structures and then come back and make those ADUs, which is a pretty strong move. It's just a lot of paperwork and you know. California is like known for this. We just add paperwork on top of paperwork. I don't understand why the city can't just cut to the chase and say, Hey, listen, we know what the goal is here. Let's just do this in one permit and save everybody a bunch of headache. But for some reason we don't do this.
Now if you have an existing multiple dwelling unit structure, which means two or more dwelling units in one structure, well, that's where there's a lot of opportunity because you could immediately build two detached ADUs, and if you have an. Existing multiple dwelling unit structure where you have eight or 10, you could now build eight detached ADUs that could be attached to each other. These are much more complicated projects and you should have an architect involved in the project at this point because you bring up like issues, fire separation issues, a DA issues. et cetera, et cetera. It's gonna be fairly complicated. If you have a multifamily zoned lot, a lot, that would allow you to build a multifamily structure with two or more dwelling units. There's also a lot of opportunity here because you could build two. Dwelling units in a, in a multiple, multiple dwelling unit structure, and then also builds two ADUs. you could basically take almost any multiple, any, almost any residential multifamily zone and build four units, in two duplexes. That would be like a reasonable way to do it. The one big gray area that neither code really addresses. Is what happens in the scenario where you have two existing single family dwelling units on the same lot. Are those supposed to follow the code for existing single family dwelling units or can that follow the code for an existing multiple? Dwelling unit structure. If you go by the word of the city's code, a multiple dwelling unit structure by definition means the dwelling units need to be in the same structure. However, I have recently had a conversation with development services department and they say that's not the way they see it, even though that's the way their code is written. the way the city of San Diego is interpreting. Multiple dwelling unit structure is different than the written code, their own written code. So the, according to the DSD, if you have two single family dwelling units on the same lot, that's considered a multiple dwelling unit structure. So a lot of gray area here. Gray area means risk for a developer. You know, you can submit something by the written. word of the code and now the development services department can have a different interpretation of their own code. So it's disappointing that a code with this language makes it into the actual code. Like how does this language make it into the code? Somebody's asleep at the wheel. I'm not really sure how, it's there. We're working with it and we're hoping that it's gonna be revised. So it's, so it provides more clarity in the next iteration of the code
21:21BaileyYeah. Well, as we've talked about often on this podcast show, oftentimes what the code says is actually much different in practice in terms of how it's applied. So people should definitely be aware of that. Um, at a high level, I imagine, like what is your opinion between. You know, obviously the state sets the ADU regulations.
How do you think the city code should interplay with those existing regulations? As far as I understand, it's only to build upon, but not necessarily to restrict further. So I could see the point of there being ev you know, every city, not just big ones like San Diego or LA wanting to have. Specific regulations to the city in, in order to like, you know, have a better quality of life for its residents and maybe take advantage of certain things, but it seems like it just adds more unnecessary complication essentially.
22:19Sean CanningYeah, so the cities have to do what the state is saying, so they have to at least meet these minimum requirements, but. I guess you have to go back to the intent. So what is the intent? 'cause you know, the, the building department also goes back to intent and they say, well, we don't think that's the intent of the code, but luckily there is no denying what the intent of the ADU regulations are. The intent is to address the housing crisis and get more Units that people can live in built, that's like the most clear intent. It's unarguable. So what, what the city should do is find a way to make this crystal clear so that there's no confusion. 'cause confusion adds risk. It adds time. It adds cost to every project. And in the circumstances where there are these, I mean, I don't, I, I don't believe there are any loopholes in the municipal code. And I have taken this up with the directors of the development service department. I said, it seems like I could get one permit to build a garage. And then get a second permit to build, to convert that garage to an ADU.
And they said, yeah, absolutely you can. what I would like to see from the city of San Diego is to say, okay, if that is permittable, let's just streamline that process. Let's just rewrite the code and you know, rewrite the municipal code to say, hey. You actually could just build two ADUs instead of going through all of this process to permit a garage, because that's just adding cost and fees and process.
It's wasting homeowners time, it's wasting development services, department's time. So let's just cut to the chase. That's what I would like to see the city do now. I think you were probably gonna ask this question as a follow up. The city of San Diego has done a good job of adding to the code with their ADU home density bonus program.
Used to be called the ADU Bonus Program. that is a great addition. There's a lot of opportunity that has been met with. Incredible opposition from NIMBY groups. and we should do another podcast about the mental gymnastics that you have to do to say you cannot build density, but also be also believe in personal property rights because the two just do not correlate. So I would like the city to simplify things. I would like the city to streamline things. I appreciate that the city has gone above and beyond with the ADU Home Density Bonus Program. But there's still a lot of work to be done here.
24:47BaileyYeah. Well, I definitely don't think it should be like an equation to figure out how many.
24:52Sean CanningMm-hmm.
24:53BaileyUnits you can build on your lot. I feel like it should be very, very straightforward. Just like a simple diagram, if this, then that sort of a deal. So, yeah. Especially 'cause when you, going back to the intents, like you just mentioned, the real intent is that any, you know, normal homeowner should be able to interpret the code and then determine what they want to build.
Not necessarily an architect with like 15 years of experience like you.
25:18Sean CanningAnd you know, before this code update, which was August of 2025. I mean, I probably had the most understanding of the previous ADU regulations in anybody in the city because how many conversations I had to have with the development service department about the previous code, and then they changed it all and you know, I've. Also been having these conversations, but you just can't get past the written language of this because ultimately it doesn't matter what anybody says when you talk to them. What matters is what they say when you submit the project. And if you submit the project and they say, no, no, no, this is what the code says, and you don't meet. requirements, you're dead in the water and you've just wasted a whole bunch of your client's time and money. So it's just gotta be updated. It's in my opinion, it's like very unacceptable that it was published this way. I.
26:11BaileyDefinitely. Are there any, um, things you wanna mention before we look to wrap up here?
26:16Sean CanningOh yeah. So I wanna talk about one of the tools that I've built to help people understand the municipal code. So lemme just do a quick screen share again here and show you what I got going on.
Okay. So let me know when you can see the screen.
26:33BaileyI can see it.
26:36Sean CanningSo, you know, my frustration with the ADU code I think I've made that pretty clear. the ADU code is updated, I try to publish what is essentially a cliff notes for understanding the ADU code. So I can share this with my clients and explain to them exactly what this means. So I just finished this document this week. it's. It's a free guide that people can download. And Bailey, maybe you can put a link to this in the notes of this meeting. But you know, when I go online on Instagram because of my search history, get a lot of offers for these free ADU guides. And I've taken a, a look at what other people are providing. And in my humble opinion, this one is the most valuable one that, that I've ever seen. This took me months to put together. It's 38 pages and it covers every single page of the municipal code. So basically on the left side here, I have actual pages from the municipal code, and on the right side I have diagrams that explain what all of this means. So. I go code section by code section, explaining it all and then offering tips on how to use these regulations or what the, what the workarounds for these regulations are. So this is a pretty cool document and I think, you know, the goal here is to provide some clarity in the city of San Diego's ADU municipal code.
28:06BaileyWe'll include a link to this directly in the description of the video so people can download it, read through it, check it out on their own time. I would say it's essential 'cause this is an update to one you had previously done a few years ago. So I would say it's essential for like, you know, people who are actually considering these projects for sure.
So they'll definitely wanna check that out.
28:27Sean CanningYeah, this document is the starting point for any ADU project, and it's also the core of all the tools I've put together. The pocket communities guide, the critical thresholds guide. This one is the core to all of those, and the other tools that I've created are peripheral to this central one.
28:50BaileySo we'll have all that. And if you guys wanna check out the other documents Sean just referenced, they're all on the homepage of the website, 10 70 architecture.com. Sean, if people are considering working with you and your studio, um, whether it be a full scale engagement or maybe they just have a couple quick questions about the developing potential of their lot, what are some resources they can go to to, uh, learn more?
29:14Sean CanningSo go to the website, 10 70 architecture.com. Check out the Instagram 1 0 7 0 architecture. This YouTube channel is filled with tons of great re resources, or you can send me an email directly to Sean, SEAN, at 1 0 7 0 architecture.com.
