Free ADU plans sound almost too good to be true.
In many cases, they are real. Cities and counties across the U.S. now offer free, downloadable ADU plans to help homeowners build faster and at a lower cost.
These plans are not free houses.
They are free architectural plans created to meet local zoning and building codes. For the right homeowner, they can save months of time and thousands of dollars.
This guide explains where to find free ADU plans online, how these programs work, and when they make sense.
- Free ADU plans can save time and design costs, but they are not free to build.
- Most free plans only work in the city or county that created them.
- Pre-approved plans often move faster through permits than custom designs.
- Free ADU plans work best for simple layouts and standard lots.
- Always confirm zoning and utility needs before choosing a free plan.
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What Are Free ADU Plans?
Free ADU plans are pre-designed layouts offered by local governments or partner organizations. They are usually created to meet local building codes and ADU rules.
Most include:
- Floor plans
- Elevations
- Basic construction details
- Options for detached ADUs or garage conversions
Some plans are fully pre-approved. Others still require site review.
Either way, they reduce guesswork and speed up the process.
Cities offer them to increase housing supply and make ADUs more approachable for everyday homeowners.
Accessory Dwelling Unit (ADU)
A smaller, separate living unit on the same lot as a primary home.
Pre-Approved ADU Plans
Plans reviewed in advance by a city to speed up permits if used as designed.
Junior ADU (JADU)
A small ADU created within an existing home, often using a bedroom or garage.
Setbacks
Required distance between the ADU and property lines.
Site Adaptation
Changes needed to make a plan work on a specific lot.
Utility Upgrades
Water, sewer, electric, or gas improvements required to support an ADU.
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Where to Find Free ADU Plans Online
Below are well-known programs that offer free ADU plans or plan sets.
Los Angeles
Los Angeles offers one of the largest libraries of standard ADU plans. Homeowners can download multiple layouts, including detached units and garage conversions. These plans are designed to meet city code and reduce review time.
San Diego
San Diego provides free ADU plans created by approved designers. The city focuses on plans that move quickly through permitting, which makes this program popular with rental-focused homeowners.
San Jose
San Jose’s ADU Ally program includes free and low-cost plan options paired with guidance. It’s a good example of a city combining design help with education.
Oakland
Oakland offers free standard plans that work well on small or narrow lots. These plans are often used for backyard rentals and multi-generational living.
Santa Cruz
Santa Cruz was an early adopter of free ADU plans. Their designs are simple and focused on affordability.
Sacramento
Sacramento offers free, pre-approved ADU plans with multiple size options. Strong program for both detached ADUs and garage conversions.
Mountain View
Mountain View provides free ADU plan sets designed to speed up permitting. Plans focus on compact, efficient layouts.
Chula Vista
Chula Vista offers free pre-approved ADU plans and publishes clear cost and process guidance, which homeowners appreciate.
Encinitas
Encinitas provides free ADU plans with coastal zoning considerations baked in. Good example of city-specific design.
Redwood City
Redwood City offers free ADU plans as part of its standard plan program. These are commonly used for backyard rentals.
San Mateo County
San Mateo County continues to expand its free plan library and offers support tools to help homeowners compare options.
Why Almost All Free ADU Plans Are in California
California cities are under state pressure to increase housing.
Offering free ADU plans helps cities hit housing goals faster, which is why most programs are there.
Other states are starting to follow, but slowly.
California Department of Housing and Community Development
HCD maintains links to many local ADU plan programs across California. It’s a helpful place to find city-specific options in one spot.
What does Free ADU Floor Plans mean?
Free usually means:
- No cost to download the plans
- No design or drafting fee
Free does not mean:
- Free permits
- Free engineering
- Free construction
- No site adjustments
Most plans still require:
- Site-specific changes
- Utility coordination
- Permit fees
- Contractor pricing
Think of free ADU plans as a head start, not a finished product.
Pros and Cons of Using Free ADU Plans
Pros
Cons
Who Free ADU Plans Work Best For
Free ADU plans tend to work best for:
- Homeowners on a tight budget
- Rental-focused ADU projects
- Aging parent or family units
- Simple backyard or garage conversions
- People who want speed over custom design
If you want a high-end look or a unique layout, a custom plan may still make more sense.
What to Check Before Using a Free ADU Plan
Before committing to a free plan, confirm:
- Your city accepts that plan set
- Your lot size and setbacks qualify
- Utility hookups are realistic
- Parking and access rules are met
- The plan works with your long-term goals
A free plan that doesn’t fit your property can cost more in revisions later.
What If Your City Doesn’t Offer Free ADU Plans?
If your city does not provide free plans, you still have options:
- Stock ADU plans you can modify
- Builder-provided ADU designs
- Architect plans reused across jurisdictions
- Pre-approved plans from nearby cities that can be adapted
These options cost more upfront but offer more flexibility.
Final Thoughts on Free ADU Plans
Free ADU plans are a smart starting point for many homeowners.
They lower the barrier to entry and make ADUs feel more doable.
Just remember, the value is in saved time and design costs. The real work still comes from permitting, construction, and smart planning.
Used correctly, free ADU plans can turn a complex project into a much simpler one.
Frequently Asked Questions
Are free ADU plans customizable?
Limited. Small changes may be allowed, but major design changes often require a new plan.
Can I use free ADU plans in any city?
Usually no. Most free plans only work in the city or county that created them.
Are free ADU plans really free?
Yes. The plans are free to download, but you still pay for permits, site changes, engineering, and construction.
Do free ADU plans get approved faster?
Often yes. Many are pre-approved or designed to match local ADU rules, which can shorten review time.
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