Permit guides

ADU Permits in Folsom: a Homeowner's Guide

Folsom's fast-track cutoff, design review triggers, and the Historic District rules — in plain language.

Last updated October 2026. Rules change; always confirm current requirements with the city before you build.

Who handles your permit

ADU permits in Folsom come from the City of Folsom Community Development Department, and there are two doors. Straightforward building permits go through the city's ePermit Center (emailed to EPC@folsom.ca.us). Anything that needs planning or design review goes to the Planning Division at PlanningEPC@folsom.ca.us or (916) 461-6202. Which door you use depends on the size of your ADU — and Folsom draws that line very explicitly.

What you can build

800 sq ftFast-track cutoff — at or under this, no Planning review

16 ftHeight limit for the fast track (grade to roof peak)

4 ftMinimum side and rear setbacks

1,200 sq ftState-law max for a detached ADU

30 ftMax ADU height outside the Historic District

60 daysState deadline to act on a complete application

The state baseline (1,200 sq ft detached, 4-foot setbacks, no minimum lot size) applies in Folsom too. What makes Folsom different is the local layer on top: design standards, height rules, and a Historic District with its own playbook.

Folsom's fast track — and its triggers

If your ADU is 800 sq ft or less, 16 feet tall or less, and at least 4 feet from the side and rear property lines, you skip Planning entirely and go straight to building permit review. That's the closest thing to a shortcut Folsom offers.

Go bigger or taller and the Planning Division steps in. ADUs over 800 sq ft must meet the city's design standards (materials, scale, privacy, lot coverage). ADUs taller than 16 feet need Director-level or Historic District Commission design review before a building permit can even be filed.

Conversions can be exempt. Turning existing space into an ADU without expanding the building footprint can qualify for a design review exemption — one of the few genuinely simple paths in Folsom.

What goes into the submittal

Building Permit Application (emailed via the ePermit Center)
Site plan, floor plans, and exterior elevations
Structural details and Title 24 energy compliance for new construction
Design Review Application first, if your project triggers Planning review

Where applications usually get stuck

The Historic District. ADUs here must respect the area's historic character, follow the city's ADU Design Workbook, and can't exceed 25 feet — or 16 feet within 50 feet of a listed historic structure.
Second-story privacy rules. Upper-floor windows near property lines may need translucent glazing, and balconies face tight limits.
Buildings close to the line. Structures less than 5 feet from a property line trigger additional building code requirements.
Guessing the door. Filing for a building permit when the project actually needs design review first just burns weeks.

Not sure where to start? That's the part we do. We check your property against Folsom's thresholds, coordinate the plans and specialists, and manage the submittal and corrections — one point of contact.

Tell us what you need help with.

Not sure where to start? That's what we're here for.

Send your project

Erik — (916) 540-8960 · Vall — (916) 956-8106
office@pcg-engineering.pro