800 sq ft ADU · checked Oct 18, 2026
800 sq ft ADU fees in San José: $12,647–$26,728, $11,331 more than at 750 sq ft
At 800 sq ft an ADU crosses the 750 sq ft line, so San José’s impact fees apply in proportion to the main home: $8,900 with a 2,000 sq ft house, against $0 at 750 sq ft. From January 1, 2027, SB 1117 limits them to the 50 sq ft over 750, which our model puts at $556.
750 vs 800
What the extra 50 sq ft changes in San José
- ADU permit issuance (incl. address): $422 at 750 sq ft → $633 at 800 sq ft
- ADU plan review: $1,137 at 750 sq ft → $1,950 at 800 sq ft
- ADU inspection (incl. meter release): $1,732 at 750 sq ft → $2,520 at 800 sq ft
- Building & Structure Construction Tax (1.54% of valuation): $2,032 at 750 sq ft → $2,167 at 800 sq ft
- Commercial-Residential-Mobilehome Park Construction Tax (2.42%): $3,193 at 750 sq ft → $3,406 at 800 sq ft
- State SMIP + building standards fees: $18 at 750 sq ft → $20 at 800 sq ft
- Parkland impact fee (ADUs over 750 sq ft): $0 at 750 sq ft → $1,700–$8,900 at 800 sq ft (exempt at 750)
- School impact fee (your district): $0–$4,035 at 750 sq ft → $0–$4,304 at 800 sq ft
Staying at 750 sq ft would save about $11,331 in fees under today’s law.
Line by line: 750 sq ft vs 800 sq ft, now and under SB 1117
Detached ADU, 2,000 sq ft main home (example assumption). The 2027 column applies SB 1117, which limits impact fees to the area over 750 sq ft.
| Fee | 750 sq ft (2026) | 800 sq ft (2026) | 800 sq ft (from 2027) |
|---|---|---|---|
| Planning & zoning | |||
| Planning review of the building permit | May apply$449 | May apply$449 | May apply$449 |
| Building permit & plan check | |||
| ADU permit issuance (incl. address) | $422 | $633 | $633 |
| ADU plan review | $1,137 | $1,950 | $1,950 |
| ADU inspection (incl. meter release) | $1,732 | $2,520 | $2,520 |
| Fire plan check + inspection | May apply$1,269 | May apply$1,269 | May apply$1,269 |
| Construction taxes | |||
| Building & Structure Construction Tax (1.54% of valuation) | Est.$2,032 | Est.$2,167 | Est.$2,167 |
| Commercial-Residential-Mobilehome Park Construction Tax (2.42%) | Est.$3,193 | Est.$3,406 | Est.$3,406 |
| Construction Tax + Residential Construction Tax (per unit) | $251–$330 | $251–$330 | $251–$330 |
| State SMIP + building standards fees | Est.$18 | Est.$20 | Est.$20 |
| Impact fees | |||
| Parkland impact fee (ADUs over 750 sq ft) | Exempt | $1,700–$8,900 | Est.$106–$556 |
| School district fee | |||
| School impact fee (your district) | Up to$4,035 | Up to$4,304 | Up to$4,304 |
| Utility connections | |||
| Sewage treatment plant connection | May apply$780 | May apply$780 | May apply$780 |
| Modeled total | $8,785–$15,397 | $12,647–$26,728 | $11,053–$18,384 |
State law
Why 800 sq ft is the size every city must allow
Local limits on lot coverage, floor area ratio, open space and minimum lot size can’t stop an 800 sq ft ADU with 4 ft side and rear setbacks, and a detached unit of up to 800 sq ft must be approved ministerially alongside a junior ADU.
San José: Detached ADU: 1,000 sq ft on lots under 9,000 sq ft; 1,200 sq ft on lots over 9,000 sq ft. JADU: 500 sq ft.
Gov. Code §66321(b)(3)
size based upon a percentage of the proposed or existing primary dwelling, or limits on lot coverage, floor area ratio, open space, front setbacks, and minimum lot size, for either attached or detached dwellings that does not permit an accessory dwelling unit with at least 800 square feet of interior livable space and with four-foot side and rear yard setbacks to be constructed in compliance with all other local development standards.
Gov. Code §66323(a)(2)
One detached, new construction, accessory dwelling unit that does not exceed four-foot side and rear yard setbacks for a lot with a proposed or existing single-family dwelling.
Gov. Code §66323(a)(2)(A)
A total floor area limitation of not more than 800 square feet of livable space.
Quoted from Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab), checked Oct 18, 2026.
FAQ
Questions about 800 sq ft adu in San José
How much are the fees for an 800 sq ft ADU in San José?
Our model of San José’s official schedules comes to $12,647–$26,728 for a detached 800 sq ft ADU with a 2,000 sq ft main home, compared with $8,785–$15,397 at 750 sq ft.
Does an 800 sq ft ADU pay impact fees in San José?
Yes: $8,900 in our model, because 800 sq ft is over the 750 sq ft exemption. Fees must be proportional to the main home; a larger house means a smaller share. From 2027, SB 1117 limits them to the 50 sq ft over 750 ($556 in our model).
Can San José stop me from building an 800 sq ft ADU?
Not with lot coverage, floor area ratio, open space or minimum lot size limits. State law requires cities to allow at least an 800 sq ft ADU with 4 ft side and rear setbacks (Gov. Code §66321(b)(3)), provided it meets other objective standards such as height.
Do school fees apply at 800 sq ft?
Yes. School fees apply above 500 sq ft; at 800 sq ft the statewide Level 1 cap is $4,304, and many districts charge less.
Not modeled yet
What these totals leave out
- Which planning and fire review an ADU gets (counted in the high total only).
- Your parcel's parkland fee zone ($1,700–$8,900 range shown).
- School district rates (statewide Level 1 maximum shown instead).
- Water meter and connection charges from your water company.
- Public Works storm and sanitary sewer fees, which the schedule lists per lot and doesn't address for ADUs.
More
Keep going
Sources
Official sources
Every figure comes from these documents; each line’s quoted text is on the San José page.
- City of San José, Planning, Building & Code EnforcementFY 2026-27 Building and Structure Permits Fee Schedule (effective August 10, 2026) (opens in new tab)
- City of San José, Parks, Recreation & Neighborhood ServicesParkland Impact Fees for ADUs (map) (opens in new tab)
- City of San JoséADU Universal Checklist (opens in new tab)
- City of San JoséADU FAQs (opens in new tab)
- City of San JoséDevelopment Construction Taxes (opens in new tab)
- California State Allocation Board (Department of General Services, OPSC)State Allocation Board item: 2026 adjustment to the Level I developer fee (meeting of January 28, 2026) (opens in new tab)
- California Legislative Information (leginfo.legislature.ca.gov)Government Code, Title 7, Division 1, Chapter 13 (Accessory Dwelling Units), incl. §66311.5 (opens in new tab)
- HCD via data.ca.govHousing Element Annual Progress Report (APR) data, Table A2: ADU building permits by year (opens in new tab)