A Homeowner’s Guide to ADUs (Video)

What an ADU is, how much they cost, the rules that matter, and how to pick a builder—explained in minutes.

Watch the Guide Get an Estimate Explore Costs
What’s inside
  • ADU definitions & types
  • Cost drivers and typical ranges
  • Permitting steps and timelines
  • Prefab vs custom & how to choose
  • Financing paths and monthly math

Watch this short guide to learn ADU basics—cost ranges, the permitting path, and how to choose a builder—plus the major financing options and what affects monthly payments.

Key moments
Download & transcript

Prefer to read? Grab the transcript or watch with captions.

Mini case studies

Detached ADU example
Detached ADU — highlights cost drivers like site utilities and finish level.
Garage conversion ADU
Garage conversion — emphasizes permitting and structural scope.

What to do next

  1. Check your local ADU rules.
  2. Compare prefab vs custom builders.
  3. Run the monthly payment calculator.
  4. Send an RFQ with your ZIP and budget.

Updated .

FAQ

What qualifies as an ADU?

An accessory dwelling unit is a secondary home on a residential lot. Common types include detached backyard cottages, attached additions, garage conversions, and prefab/modular units placed on a new foundation.

How much does an ADU typically cost?

Costs vary by location and scope. Major drivers are size (sq ft), site work and utilities, structural upgrades, and finish level. Detached builds usually cost more than garage conversions. See current ranges on our Costs page.

How long do permitting and construction take?

Design and permitting commonly span a few months, then construction ranges from a few months for conversions to longer for ground-up builds. Timelines depend on your city’s review speed and the complexity of the site and design.

Where can an ADU go on my lot?

Placement is controlled by setbacks, maximum height, lot coverage, and utilities access. Rules are city- and state-specific, so check your local summary on Regulations before you finalize layout.

Prefab or custom — which should I choose?

Prefab can speed schedules and reduce on-site disruption, but offers less design flexibility and may have transport/set craning limits. Custom lets you tailor layout and finishes and navigate tricky sites, with more design and build time. Our Builders guide compares options.

Can I rent my ADU?

Long-term rentals are widely allowed; many jurisdictions restrict short-term rentals under 30 days. Always confirm local rules and any owner-occupancy requirements on the Regulations page and your city’s planning portal.

How do people finance an ADU?

Common paths include HELOCs, cash-out refinance, construction loans, and (in some cases) renovation loans. Compare pros/cons and monthly payment examples on Financing.