How Long Does It Take to Build an ADU in Sacramento?

What are the phases of an ADU build?

An ADU moves through four phases. Knowing how long each takes sets honest expectations — and shows where the schedule can be shortened.

What makes an ADU build faster?

• Pre-approved / shelf-ready plans cut plan check to about 30 days
• A garage conversion or JADU skips foundation and framing time
• A complete, accurate permit submittal keeps the 60-day clock running
• A flat, simple infill lot avoids grading and site-work delays
• One accountable design-build team (no handoffs between architect, engineer, and GC)

See also:Pre-approved plans (glossary)

What slows an ADU build down?

• Full custom design and engineering versus a proven plan set
• Incomplete applications — the 60-day permit clock won't start
• Foothill or sloped lots (Folsom, El Dorado Hills, Auburn) needing grading or retaining
• Septic, well, or panel upgrades discovered late
• HOA architectural review in master-planned communities

Does ADU type change the timeline?

Yes. A Junior ADU or garage conversion can finish in roughly 4–6 months because it reuses existing structure. A new detached ADU runs 6–9 months because it needs a foundation, framing, and full utility connections. Multigenerational and larger custom units sit at the top of that range.

See also:Garage conversion ADU · Detached ADU

How long does each phase actually take, week by week?

The headline 6–9 months hides a lot of variation, so it helps to see where the weeks go. Design and engineering runs 2–6 weeks: a pre-approved or shelf-ready plan can be ready in days, while a full custom design with structural engineering and Title 24 energy calcs takes the longer end. Permitting runs 4–10 weeks against California's 60-day approve-or-deny clock — about 30 days when you submit a jurisdiction's pre-approved plan because the design has already cleared review. Construction is the longest stretch at 12–16 weeks for a detached unit, because it includes the foundation, framing, mechanical/electrical/plumbing rough-in, drywall, finishes, and a string of inspections that each have to pass before the next phase starts. Final inspection, the utility meter set, and your walkthrough add a last 1–2 weeks.

Those phases don't run back to back without gaps. The schedule's hidden time sinks are the handoffs between them — waiting for a plan-check correction, waiting on a utility company to set a meter, waiting for an inspector slot. A single design-build team that owns design, permitting, and construction closes most of those gaps, which is why design-build ADUs tend to land at the shorter end of every range.

Does where you build in the Sacramento region change the timeline?

Yes — the building takes about the same time to frame and finish anywhere, but the site and the permit counter around it move the clock. Flat infill lots in the city core and the I-80 / Highway 50 suburbs are fastest: simple site work, common pre-approved plans, and a permit office that processes ADUs routinely. Foothill submarkets — El Dorado Hills, Auburn, Cameron Park, Loomis — run longer because slope, rock, and longer utility trenches add site-work weeks, and some parcels sit in high fire-severity (WUI) zones that trigger extra review. Which jurisdiction governs your address matters too: the City of Sacramento, Sacramento County, and the surrounding city and county offices each run their own queue, and a unit that needs septic instead of a sewer connection adds design and approval time on unsewered lots.

• Flat infill / core (Sacramento, Citrus Heights, Rancho Cordova): fastest — simple site work, pre-approved plans common
• Established suburbs (Elk Grove, Roseville, Folsom on flat lots): mid — own city permit queues, mostly routine
• Foothill / sloped (El Dorado Hills, Auburn, Loomis): slowest — grading, rock, longer utility runs, possible fire-zone review
• Unsewered lots: add design and approval time for septic capacity and any system expansion

See also:Sacramento ADU rules & permits — which office governs your lot

Why does the 60-day permit clock sometimes feel longer?

California law requires a jurisdiction to approve or deny a complete ADU application within 60 days — but the word doing the work is 'complete.' The 60-day clock only starts when your submittal has everything the office needs: site plan, floor plans and elevations (or a pre-approved plan number), Title 24 energy documentation, structural calcs, a utility plan, and any soils report the lot requires. Submit a package that's missing a piece and the office issues a correction notice; the clock pauses and only restarts when you resubmit complete. That's why two owners with identical lots can have very different permit experiences — one front-loaded a complete application and cleared in 30–60 days, the other traded correction letters for months.

The practical takeaway: the fastest permit isn't the one you rush out the door, it's the one that's complete the first time. Using a jurisdiction's pre-approved or shelf-ready plan set is the single biggest accelerator because the design has already passed plan check, which is how the timeline compresses to roughly 30 days.

See also:What an ADU costs in Sacramento — including permit fees

What can you do before signing to shorten the timeline?

A lot of the schedule is set before construction ever starts, and the prep you do up front is where the biggest weeks are won or lost. Confirm your lot is feasible early — easements, fire zone, septic capacity, and which jurisdiction permits your address — so nothing surprises the project mid-stream. Lean toward a pre-approved or shelf-ready plan if it fits your goal, since it skips most of the design phase and shortens plan check. Line up financing in parallel with design rather than after permits, so funding is ready when construction is. And pick one accountable design-build team instead of stitching together a separate architect, engineer, and general contractor, because every handoff between separate vendors is a gap where the schedule leaks.

• Run a feasibility check first — catch easements, fire-zone, or septic issues before they cost weeks
• Choose a pre-approved / shelf-ready plan where it fits — skips most design time and shortens plan check
• Line up financing in parallel with design, not after the permit is issued
• Keep size under 750 sq ft to skip impact fees — fewer fee steps, and it trims the all-in cost
• Use one design-build team so there are no handoffs between architect, engineer, and contractor

See also:Get a free feasibility check

How do you keep an ADU project on schedule?

The schedule holds when one team owns design, engineering, permits, and construction — no gaps between separate vendors — and when payments are tied to inspected milestones so work keeps moving. That's how Upside structures every build; we scope site conditions up front so nothing surprises the timeline mid-project.

See also:How Upside builds your ADU · Talk to a builder