Backyard studio
Generally used as an accessory room for:
- office work
- art and creative work
- exercise
- music
- hobbies
- other daytime activity
It may include:
- electrical service and lighting
- heating and cooling
- insulation
- finished walls and flooring
- windows and exterior doors
The Cost Planner on this site excludes:
- plumbing
- a kitchen
- a bathroom
- sleeping accommodations
- independent dwelling use
Accessory dwelling unit (ADU)
An ADU is generally a separate dwelling unit for independent living on the same lot as a primary home. It commonly includes:
- sleeping space
- cooking facilities and a kitchen
- sanitation facilities and a bathroom
- plumbing, water, and sewer or septic connections
- dwelling-unit code requirements
Why ADUs generally cost more
- Plumbing: supply and drain lines, fixtures, and venting.
- Sewer and water: connections that may require long trenches, pumps, or utility approvals.
- Kitchen: cabinets, counters, appliances, and dedicated circuits.
- Bathroom: fixtures, waterproofing, ventilation, and finishes.
- Energy code: full dwelling energy compliance for the envelope and systems.
- Life safety: smoke and carbon-monoxide alarms, emergency escape openings, and fire separation as required.
- Professional design: full drawings and often engineering.
- Utilities: larger electrical service and possibly separate meters.
- Permitting and inspections: a complete residential permit set with more inspections.
- Impact and connection fees: some jurisdictions charge them for new dwelling units.
- Schedule: longer design, review, and construction.
Side by side
| Topic | Backyard studio (as planned here) | ADU |
|---|---|---|
| Typical use | Office, art, exercise, music, hobbies, daytime activity | Independent living, including sleeping |
| Plumbing | None in this planner | Water and sewer or septic |
| Kitchen | No | Usually required to count as a dwelling |
| Bathroom | No | Yes |
| Sleeping | Not intended | Yes |
| Utilities | Electrical; sometimes data | Electrical, water, sewer, sometimes gas; possibly separate meters |
| Codes | Accessory-structure, electrical, mechanical, energy as applicable | Dwelling-unit requirements, life safety, energy code |
| Permitting | Varies; often zoning plus trade permits | Full residential permit set; often impact or connection fees |
| Address | Usually none | May receive its own address |
Legal definitions vary
What counts as an ADU, a “habitable accessory building,” or a simple accessory structure is defined locally. Some jurisdictions regulate a room differently based on whether it has a sink, a toilet, or a closet, or on how it is used. Omitting plumbing does not automatically make a structure legal or permit-exempt; it may still need zoning approval and building, electrical, mechanical, or foundation permits.
If you might want sleeping use, a bathroom, or a rental in the future, tell your local planning department at the start. Designing for it later can be far more expensive than planning for it now. Read the permit guide.