What is a detached ADU?
A detached ADU is a complete home that stands on its own in your yard, with a kitchen, a bathroom and its own entrance. It shares the lot, but not a wall, with the main house. Many owners call it a backyard cottage or a casita.
Can I use one of Fresno's free plans?
Often. As of October 2026, the City of Fresno offers five pre-approved ADU plans, each in Craftsman, Contemporary or Gable styling:
- Plan 1: studio, one bath, 340 sq ft.
- Plan 2: one bedroom, one bath, 499 sq ft.
- Plan 3: one or two bedrooms, one bath, 625 sq ft.
- Plan 4: the Plan 3 layout built over a garage.
- Plan 5: three bedrooms, two baths, 1,015 sq ft.
The plans include solar panel drawings. A city plan still needs a site plan for your lot, and it only works where the footprint fits. More in our free plans guide.
Where can a detached ADU go on my lot?
State law caps side and rear setbacks at 4 feet for a new detached ADU of up to 800 sq ft, and a city may not use a front setback to block that unit. Height is generally limited to 16 feet. Utility lines, easements and existing trees often decide the exact spot more than the setback lines do.
Will a detached ADU trigger impact fees?
Not if it stays at 750 sq ft of interior living space or less. As of October 2026, Government Code §66311.5 bars impact fees below that size, and larger units pay in proportion to their square footage. School districts cannot charge fees on units under 500 sq ft. Four of Fresno's five plans, counting the living space in Plan 4, come in under 750 sq ft.
What does a detached ADU need that a conversion does not?
- A new foundation, framing and roof.
- Longer runs for water, sewer and power, often across the yard.
- Solar panels under the California energy code for most new detached units.
- Cooling and insulation sized for long, hot Fresno summers.
Is a detached ADU worth the extra cost over a conversion?
It depends on what you are starting with. If you have no garage, or the garage is too damaged to save, new construction may be the only real path. If the garage is solid, converting it usually costs less. We price both when both are possible, so you can compare on paper.
How much does a detached ADU cost?
As of October 2026, Block Renovation's 2026 Sacramento guide lists detached ADUs at $150,000 to $300,000 or more, or about $300 to $500 per sq ft. We found no Fresno-only figure. Details are in the Fresno ADU cost guide.
Related
As of October 2026. Sources: City of Fresno ADU Program page; HCD ADU Handbook (March 2026); California Government Code §§66311.5, 66321 and 66323; Block Renovation, Sacramento ADU Costs 2026.
Find out what fits in your backyard
Send the address. We check setbacks, easements and utility routes, and whether one of the city plans fits your yard.