San Diego ADU Garage Conversion

4 Replies

I just bought a duplex and I'm looking to convert the garage into an ADU and was looking for some guidance on the process and any recommendations on ADU specialists, planners, contractors etc.

A bit about the property - the duplex consists of 2 detached buildings. The one in front is a 2 bed / 1 bath unit and the one in the back sits on top of a 3 car garage and is also 2 beds / 1 bath. The 3 car garage is actually a 2 car garage separated by a wall from a 1 car garage (which the tenants in the front unit use to park their car).

I am looking to convert either the 2 car garage into a studio and keep the 1 car garage for tenant use, or convert all 3 car garages into a 2 bed / 1 bath. Of course, I would get more rent converting the entire thing to a 2 bed/1 bath, and have everyone use street parking. There is ample street parking since the property is near a cul de sac like part of the neighborhood. However, I'm not sure value wise, which option makes the most sense since some people really value garage parking. This is San Diego though, so it's not like harsh weather would be a problem.

I am also wondering what the process is like to do this conversion. The first steps I think is to get a permit and find ADU planners to create a floorplan and get some quotes. I am looking for any recommendations or guidance on the procedure to go about building an ADU. I'm hoping to do this conversion within the next few months or year - the sooner I get started on the permit process the better, since I've heard it takes months to get permits.

Also I'm not sure how much the entire project would cost. Since there's already a 2bed/1bath unit above the garage, it would be easier and cheaper than erecting a completely new standalone structure. I've heard anywhere between $100-300+ per square feet but have no clue what price I should be expecting to pay for the conversion.

Any tips / advice / recommendations / referrals are welcome! Thanks!

@Cathy Song The primary decision here is how much you want to do yourself (and learn in the process) or how much you want to have done for you (and pay someone else). If you have no plans to do this again, search for "San Diego ADU" in Google, then watch how every ad across the internet is for a retail design / remodeling / "ADU Consultant" / contractor who is looking for customers like you. People or groups purpose-built to sell retail ADU services are sprouting up everywhere. Or, get a referral from someone who knows someone.

The other option is to put the pieces together and quarterback the project yourself.  Honestly, not something I'd suggest unless you really *want* to do it ... but is less expensive and is how real estate investors make a living doing this.

The first and most important thing to figure out is whether your current duplex conforms to current zoning. If it does, converting the garage is going to be a pretty simple exercise. If it was downzoned at some point, the City will look at your existing second unit as your ADU and won't allow a third unit. You can figure that out easily by looking up your address online.

FWIW, I literally broke ground last week on a property where we're building a new construction 3 car garage in the back with a 2bd/1ba unit over it.  I elected not to make the garage living space (though I could have permitted it as so) in favor of giving tenants parking and storage.  Every case is different when making that tradeoff decision.   

Hi @Cathy Song ! That sounds like a fun deal! I've been obsessively researching ADUs for a bit now and am looking to connect with other Californians who are going that route. In terms of recommendations, there's a lot of stuff out there. Check out Ryan who's based in Napa with How-To-ADU ( He's got some helpful videos, resources, etc. There are also good groups down in your neck of the woods. 

I'm short on time at the moment, but what I can say is that most of the specialists will tell you that it can be just as or more expensive to convert space into an ADU as to build one ground up. What I've found personally is that the devil is in the details. Your specific property will impact the costs (age, layout, access to water lines, etc) a great deal. Also, your city's regs and policies are a big deal. Some will require you to get a separate sewer hookup for each unit and charge you an obscene amount. Others will let you tap into the existing and charge little or nothing. I'd start by trying to find local people/groups that specialize in anything ADU and get their take on your job. Hope this helps!

@Cathy Song

You are definitely in the right mindset of trying to maximize your rents by using the available space. I'm actually going through a similar process where I'm converting my 3 car garage on a single family rental to a 2/1 ADU. This is my first investment and I quickly realized that ADU's are the way to go to be able to make deals work in our expensive market. I 100% also agree with @Justin R. on the options for your project. I personally chose the DIY method because I'm greatly maximizing my ROI's and I'm learning the process along the way. In the future it might be different for me. Feel free to PM me any specific questions and id be happy to help in any way.