Free ADU Floor Plans if you don’t have an architect
Every Accessory Dwelling Unit starts with a floor plan
Working on a floor plan is an integral early step toward getting an Accessory Dwelling Unit.
Whether you’re building a detached or attached ADU, or just converting a part of your existing home, you will need plans (and even completely prebuilt modular units have plans!)
It’s a key step and here’s why…
Plans are a crucial part of the permitting process
And they’re key for your design, build and budget
For this article, I’m maintaining a list of free Accessory Dwelling Unit design drawings and floor plans that you can use to inspire your ADU project.
The list includes ADU floor plans of various sizes ranging from 224 sq ft up to 1,200 sq ft. They’re primarily for detached ADUs.
Homeowners often ask if they can download some floor plans and use those to submit for permits. To be clear, it’s more complicated than that. To help, I’ve pulled some information together about how to use floor plans and design drawings, and what the next steps are before you can submit for a permit.
Even if you use free ADU floor plans, there will be more work you need to do to turn these into a full plan set.
And lastly, I’ve tucked in some alternative ways to get plans at the end in case you want to keep researching.
As always, this is not legal advice - the information on this website is presented as general information. You should speak to a licensed professional in your jurisdiction and work with local agencies on your project!
The list of ADU FLOOR Plans
There are a lot of ways to get floor plans for your Accessory Dwelling Unit (ADU)
These plans are courtesy of San Diego County
The following need to be added to the above table:
San Mateo County: https://www.heartofsmc.org/programs/adu-center/
Pre-designed government-commissioned floor plans
This is the gold standard for free plans.
To make it easier to plan and build Accessory Dwelling Units, some cities and counties have commissioned plans.
The plans I feature most prominently in this article are the San Diego County standard ADU plans for several different unit sizes, with files that you or a designer/architect/builder can modify in CAD (Computer-Aided Design).
If you’re computer-savvy and you want to modify the files, you should download some CAD software. I used sketchup when working on my own house plans. It was hard to get the hang of it, but looked pretty great at the end of the day.
These were specifically designed by an architect who was thinking about ADUs to be built in unincorporated San Diego County. And they’re intended to be used so it looks like the county has paid for them to be distributed and reused.
These plans are Type V (type 5) construction meaning they use all conventional materials that are up to state code in California.
More ADU plan resources
In addition to the County of San Diego “county standard” plans mentioned above, there are several other jurisdictions that have put out ADU plans.
The city of Encinitas (down by San Diego) offers “Permit-Ready” plans.
The city of San Jose has pre-approved vendors who each have pre-approved “Build-ready” plans. If you want to work with those plans, you have to contact the builders. At the time I’m writing this, the three pre-approved vendors are Acton ADU, Abodu, and prefab ADU.
The city of Santa Cruz offers ADU prototypes that you can use for inspiration. Click on the powerpoint links to download presentations that include floor plans.
Humboldt County has commissioned ADU floor plans for detached, attached, and above the garage construction.
And an honorable mention from Hawaii where they’ve put a floor plan book together using San Diego’s plans, among others.
Downside of ADU floor plans on government websites
A downside of these plans is that they are not always updated when building code changes (see the Humboldt County plans “requiring correction” for an example)
Additionally, plans from one city or county may not be translated directly to another jurisdiction without some tweaks.
Can you do this without an architect?
In California, according to Sections 5537 and 6737 of the California Business & Professions Code, homeowners can often prepare plans, drawings and specs for wood-framed residential homes less than 3 stories without an architect.
Most ADUs and JADUs will fall under this definition.
One notable exception I’ve heard of is if you have a basement or attic that puts you over the 2 story limit based on the local agency’s interpretation (some cities and counties allow 2 stories PLUS basement, others count the basement as a story). Exceptions like this can be scary…
But don’t worry - in the next part of this article, we’ll go over the next steps for how to use your free ADU plans and drawings - and this will cover any unexpected surprises.
How to use free ADU floor plans and drawings
Best to think of these as “Starter Plans” or “Design Drawings” because you’ll still need to do some work before submitting for planning or building permits.
Architects sometimes refer to this stage of drawings as schematic designs or preliminary design development.
Every property is unique so you still need to do some important work with these plans based on the specific site and the orientation of the ADU.
If at any point in this article you start feeling overwhelmed, don’t worry - that’s normal. Just email hello@how-to-adu.com (or fill out this form to get started) and let us help you out.
If you want to handle it on your own, that’s very feasible in most cases - it will just take time and research, so read on...
Planning requirements for ADU house plans
Once you have ADU floor plans you like, you want to find a permit checklist for your local planning department.
This checklist can be very intimidating for a layperson, but we can break down some of the common requests.
The planning checklist will often include the following sections:
Property information
Plan set checklist
Required applications and forms
Applicant’s affidavit
If they don’t have a checklist online, I highly recommend going in with your starter plans or design drawings and your street address and starting a conversation with the planners.
You tell them you’re thinking about building an ADU and want to talk to them before getting too far into the process. This is also a good time to get a temperature for how friendly or defensive they are about ADU development.
Here’s what you should expect...
Typical next steps for ADU plans
Even though you already have a floor plan, you probably need several other types of plans for your permit. The full list will be in the permit set the city or county requires.
It can typically include:
Floor plan
Building elevations
Site plan / Plot plan
Grading plan
Drainage plan / Stormwater control plan
Boundary survey
Roof plan
Electrical plan
Foundation plan
If you use the plan set from San Diego County, they include foundation plans, electrical plans, roof plans, floor plans and elevation drawings.
Here are some examples to illustrate why it’s important, and why it’s hard to buy these online or get them for free…
ADU SITE PLANs
Even though you already have a floor plan, you probably need a site plan for your permit.
example of plot plan,
courtesy of San Diego County
Site plans (or plot plans) will show how your proposed project will interact with existing conditions on the property and on neighboring properties.
Here are some questions a thorough site plan will likely answer:
Where is the ADU sitting on your property?
Setbacks:
How near/far are you from the property line?
How near/far are you from other structures?
What is the relation between the ADU and any existing easement?
Grading and drainage:
What is the slope of the land?
How does the slope affect your foundation?
Where does the stormwater drainage go?
You can understand why the city or county want to know all this, but you can also understand how it’s impractical to buy this off a website from a person who has never visited your property.
ADU Elevation drawings
example of ADU elevation drawings,
courtesy of San Diego County
Another example of a typical requirement for a planning or building permit is elevation drawings (internal conversions like garage, basement or spare room conversions are often an exception to this).
You can hire a draftsperson which can be less expensive than an architect. (I’d be happy to recommend a draftsperson in your area if you share your project information with me.)
DO YOU NEED AN ARCHITECT AFTER ALL?
If you’re reading all of this and thinking you can’t do it all on your own, you have other good options.
You can choose a contractor who will work on your plans with you
You can work with a permitting specialist who will project manage the planning and entitlements for you
You can handle almost everything yourself and contract out specific bits as they come up (e.g. hiring a draftsperson for the elevation drawings, hiring a surveyor if the planning department requires extra boundary work, etc.)
No matter which of these options you want to explore, How To ADU can help. Get started by sharing your ADU project with us.
Save Money with Proper ADU Planning
While you’re doing this work, these ADU plans can also help you with your planning and design.
They’re more than a bureaucratic technical requirement!
Save money with value engineering
Let’s say you have plans that you’re ready to submit to the city or county.
This is a great example of value engineering - by tweaking his design, and changing his exterior shear wall to an interior shear wall, Hektor saves $10k
This might be a great time to run it by an ADU specialist like me, or by a contractor with a lot of ADU experience who you plan on working with.
That contractor can value engineer your plan (ie find ways to save money based on your specific site and project).
Here’s an example: it is incredibly beneficial for you to start thinking about utilities now, whether the planning department requires it or not.
You can save yourself tens of thousands of dollars by having a professional think about how this plan will fit onto your lot.
If you think about your plumbing and how it connects to the primary residence at this stage...
The difference between a design that uses gravity to connect to the main house’s sewer, and a design that is forced to connect to the sewer main at the street, can be $10k-$20k -- so it definitely pays to have a professional look at your plans at this stage.
GREAT DESIGN IMPROVES QUALITY OF LIFE
Furthermore, thinking about basic design elements at this stage can really increase the quality of life in your ADU, and its curb appeal.
Here are some great questions to ask while you’re still in the planning stages:
Where are the windows?
What’s the light like in that part of your property at different times of day?
Is the new house going to be blocking the light or view of the primary residence?
Do you like how the ADU interacts with the primary residence?
Is there enough privacy for both parties? Should you move the ADU entrance to be less visible from the primary residence?
This is the right stage to book an ADU expert to look at your project and make sure you’re not making any costly mistakes, or leaving good opportunities on the table.
Alternative ways to get ADU house plans
The AARP Livable Communities Initiative - Technical Drawings
Buy plans online
There are lots of market places that help you draw up plans like House Plans Pro
You can even buy ADU floor plans on Etsy!
Vintage architecture books
I personally adore this option and you see me use it in my videos on youtube
I’ve got a copy of Paul Revere Washington’s book New Homes For Today and I love it.
He was a big deal in Los Angeles in the mid-century and a bit of Hollywood’s golden age, an amazing chameleon of an architect, and a person of color who had to overcome a lot of prejudice to establish himself as a prominent architect in the region. I can’t wait for the movie one day.
I don’t want to get into the rabbit hole of architectural copyright law (which is a fun, and complicated rabbit hole full of twists and turns)... but I will say this: the copyright act didn’t protect architectural work until 1990 and even now, if you walk around your house taking measurements and draw up plans based on that, it is okay.
After all it’s your house - your ability to utilize the actual dimensions is protected. Now if you do what I’m doing in this section (copy) a plan and it’s protected (registered after the 1990 copyright act) then that’s against the law.
Pinterest for architectural inspiration
I’ll maintain a pinterest board with inspirational ADU floor plans - Use this for ideas. That said, when you’re browsing Pinterest, some of the ideas you see will be protected by copyright law. Be nice - don’t steal.
If you see work you love, try to find the architect or designer responsible and see if you can work with them.
Draw your own plans
If you’ve read this far, there’s a good chance you’re seriously considering doing all this on your own.
Power to you. It’s completely possible.
Make sure you’re doing it because it’s fun, and not because you want to save money.
It’s very possible to do this on your own. There’s a fair chance you’ll make a mistake that costs you a lot of time or money - so I wouldn’t recommend this as a strategy for saving time or money. That said, it’s hugely rewarding if you enjoy doing this yourself, so I would recommend doing it for that reason.
If you look at some of the plans that are available online, you don’t need to be a Rhodes Scholar to put a plan together. And you can always hire a professional builder-designer to get their feedback on your designs.
People do this every day and if you can get over the intimidation factor, you can definitely go this route.
Get started
Planning and building an ADU can be a pretty daunting process, but we’re here to help.
Get started by sharing some information about your potential project.
You will save a lot of money by reading articles like this and consulting ADU specialists ahead of time.
Every project is unique, and we can’t wait to help you succeed.