← PCG Engineering
Permit guides
ADU Permits in Suisun City: a Homeowner's Guide
Suisun City runs ADUs under the state framework — here's what that means for your project, in plain language.
Last updated October 2026. Rules change; always confirm current requirements with the city before you build.
Who handles your permit
In Suisun City, ADU permits run through the city's Development Services department. The city publishes relatively little ADU-specific material, so the operative framework is California's state ADU law — which applies directly and sets the baseline for setbacks, sizes, and the ministerial review timeline. For questions specific to your parcel, contact Development Services directly; encroachment permits (for work in the public right-of-way, like driveway or sidewalk modifications) go through (707) 421-7340.
What you can build
1,200 sq ftMax for a detached ADU under state law
16 ftHeight limit for most detached ADUs
4 ftMinimum side and rear setbacks, detached ADUs
1 + 1One ADU plus one Junior ADU per single-family lot
$0 feesNo impact fees for ADUs under 750 sq ft statewide
60 daysState deadline to act on a complete application
Small-city realities worth knowing
- State rules are the local rules. Suisun City processes ADUs under California's ADU statutes — the 4-foot setbacks, 1,200 sq ft cap, and 60-day ministerial clock are your framework.
- Low-lying geography. Suisun City sits near the marsh and the flood-prone areas around the slough — check flood-zone status for your parcel early, since it can trigger elevation or foundation requirements.
- Encroachment permits are separate. Any work touching the public right-of-way (driveway approaches, sidewalk, utilities) needs its own encroachment permit — (707) 421-7340.
- Pre-application contact pays off. In a smaller department, one conversation with staff can resolve utility, setback, and flood questions that would take rounds of corrections in a bigger city.
Check the flood map first. Suisun City's proximity to the marsh means flood-zone status is the single most likely surprise on a parcel here. Confirm it before spending a dollar on design.
What goes into the submittal
- Building permit application to Suisun City Development Services
- Site plan: lot lines, structures, setbacks, easements, utilities, drainage
- Architectural plans: floor plans, elevations, sections
- Structural plans and calculations, Title 24 energy documents
- Electrical, plumbing, and mechanical layouts
Where applications usually get stuck
- Flood-zone surprises. Discovering floodplain status during plan check can restart the foundation design.
- Skipping the pre-application step. Small cities reward an early conversation; skipping it usually means more correction rounds.
- Right-of-way work without a permit. Driveway or utility work in the street without an encroachment permit creates enforcement headaches.
- Incomplete energy documents. Missing Title 24 forms are a perennial first-round correction everywhere.
Not sure where to start? That's the part we do. We check your parcel against the state rules and Suisun City's local requirements, coordinate the plans and specialists, and manage the submittal and corrections — one point of contact.