Permit guides

ADU Permits in Morgan Hill: a Homeowner's Guide

What you can build, which permits you need, and how the review actually works — 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 go through the City of Morgan Hill Development Services Department — Building & Fire Prevention and Planning — at 17575 Peak Avenue. Before you apply, the city asks you to contact planning staff at planning@morganhill.ca.gov to confirm your zoning and any extra requirements — before paying for plans, not after. Plan review status is checked in the eTRAKiT citizen portal.

What you can build

California state law sets the baseline, and Sunnyvale follows it:

1,200 sq ftMax for a detached ADU

50% / 1,200Max for an attached ADU (50% of the main home, up to 1,200 sq ft)

500 sq ftMax for a Junior ADU, carved from existing space

16 ftHeight limit for most detached ADUs (18 ft near major transit)

4 ftMinimum rear and side setbacks for detached ADUs

1 + 1One ADU plus one JADU allowed per single-family lot

There is no minimum lot size for an ADU under state law. Converted garages and other existing structures keep their current footprint — no new setbacks apply to the conversion itself.

Pre-approved plans: the ADU Plans Gallery

Morgan Hill's ADU Plans Gallery (morganhill.aduaccelerator.org/gallery) lists ADU designs — including plans pre-reviewed for building code — from designers and builders. Pick a design, connect with the designer to use or purchase it, then complete site planning for your property.

The city's own note is worth reading twice: all plans — even pre-approved ones — still require customized site planning and permitting: placement on the lot, emergency access, foundation design. Gallery plans are general, not property-specific.

Pre-approved doesn't mean permit-free. Expect additional Planning and Building review of the property-specific elements — foundation, placement, access — on top of the pre-reviewed design.

What goes into the submittal

Prepare the plan set. The city publishes detached and attached ADU checklists (also in Spanish); plans must be drawn to scale on minimum 24"x36" sheets, in enough detail to demonstrate code compliance.
Budget by valuation, not flat fees. Plan check and permit fees are calculated from total construction valuation, and plan check fees are paid before review starts — get the preliminary fee estimate before you commit to a size.
Corrections and fees. Impact fees apply only at 750 sq ft and up, in proportion to the primary dwelling's floor area. Deferred submittals like truss calculations can trigger extra review fees; flood zones add a flood-zone review.

Where applications usually get stuck

Skipping the pre-application zoning confirmation — zoning surprises are expensive after plans are drawn.
Valuation-based fees — design decisions move the fee bill, so get the preliminary estimate early.
Treating a gallery plan as permit-ready — emergency access, foundation design, and site placement still go through full review.
Flood-zone review — an extra layer with its own fee; check the FEMA maps before you design.

Not sure where to start? That's the part we do. We look at your property, map the requirements, 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