Finding the Right Property
Finding a property that was optimized for an ADU was a prerequisite back when my wife and I were looking for houses to buy. Granted this was in 2018, when the ADU rules in California were significantly more stringent. Still, I knowing that we wanted an ADU before we bought was helpful as we considered each property and how it would cater to the needs of building and renting an ADU. Here are some of the things we considered:
Legality - Would we be legally able to build an ADU at the property? If so, what were the size limitations (sq ft and height)? Is it zoned to allow ADUs, or is it zoned a “historic landmark?” Is there an HOA? Often times they have rules preventing development of ADUs. To answer these questions, I recommend the following
For a quick and easy assessment, check out a site like Housable.com and enter the property address. They’ll give you instant results to get you started.
Before making an offer, check with the local permitting office and ask them about the ADU rules for the parcel number
If you still have questions, you can pay for a consult with someone like Ryan from HowToADU who specializes in this stuff.
Property Layout - As you evaluate properties, think about how and where the space is distributed. If you already know you want a detached ADU, than you will need space to build it, unless you’re converting an existing structure (like a garage). Just because a property has 1/4 acre of land, doesn’t mean it’s usable. If you’re looking to add on to the main house (primary dwelling), look for obvious and creative ways to segment the space. Will the two units share a washer/dryer, or will they each have their own. Consider these things:
Is the grade flat or sloped? Flat is easier and more cost to develop, but you can still build on a grade. The grade also determine where water will flow and whether your sewer will need a pump to get to the main.
How is the soil and tree coverage of the build site? Removing trees sometimes requires a permit and adds to the costs. The soil may impact your foundation type, based on thinks like expected movement there is and how far down bedrock is. Generally the soil is similar in the wider area, so I’d recommend talking to neighbors or builders in the neighborhood to earn more.
Is there construction vehicle access to the build site? Depending on your ADU, you may need large trucks and equipment to access your yard. Some prefabs need to be dropped in via a crane. Constructing ADUs will be more cost effective (and faster) if the contractors can drive up close to the building site.
This is also a good time to consider where your tenant(s) will park their car. Some jurisdictions require a parking spot to be made available, although this rule has been removed for California. Beside the legal component, put yourself in the shoes of a tenant - you’d want a dedicated parking spot. Additional value for covered parking and EV chargers.
How much privacy is there between the potential building site and the existing house. Consider where the windows and walls are in the house and where you envision people spending the most time (both inside and outside the home). Would you feel uncomfortable sharing your backyard with a tenant? Think about how you could use tree foliage, fencing, or window placement to maximize privacy between the two units if they’re detached from each other. If they’re going to be attached, reduce shared walls to increase privacy.
How will you run utilities to the ADU?
For detached ADUs, a greater distance will drive costs up. For sewer, note the elevation of the build site which will determine whether you’ll need a pump to get waste to the main. Equally important is where you can run the line without tearing up landscaping, especially where you are tying in to the existing lateral. For water, you should know how big your water line is (1/2” or 3/4”) and where it connects to the house. The water line dimension probably won’t matter unless the primary dwelling is large and has a lot of landscaping, in which case 1/2” is probably too small. For electrical, you need to check how many Amps the electrical service is to the existing home. If 100A, you’ll probably need to replace the panel and increase to 200A ($2,500 -$3,000). If you think you want gas in the ADU, you’ll again need to note the dimention of the gas service line to the house and whether there’s access to trench a line to the build site. Lastly, I recommend you run a sleeve for “coms” (internet) as long as you’re digging these trenches. The hardwired connection will always be faster and give you options to future proof the house.
If you’re evaluating an attached ADU, you still need to identify where the utilities can be accessed and whether there’s enough headspace for each, but you shouldn’t need to worry about running new trenches.
Permitting Friction - Just because some rules say you can build an ADU, doesn’t mean a city is going to roll out the carpet and make it easy for you. We found this out the hard way, and I wish we had done some due diligence before hand (although it wouldn’t have changed the outcome). Sometimes it’s completely luck of the draw based on the permit technician you’re assigned to. There’s a HUGE range in ADU friction from city to city. Some cities have pre-approved plans that will let you fast-track your permit and online portals for speedy submissions and responses. Other cities have intentionally made it impossible by declaring the entire city a historic zone, or jacking up application fees.
Talk to some builders who’ve built in your area. I was able to learn a ton by asking the leadership team at Housable what cities are the best and worst to work with for ADUs (They told me West Sacramento is the worst in case you’re wondering).
Look at the resources available online from the building department of the property you’re considering. If they have a lot of info online, that means they’re at least making the effort to put out clear information, and they’re likely going to be easier to work with.
