San Diego ADU Height Limits: Can I Build a Two-Story ADU?

Direct Answer

San Diego guidance allows some ADUs to reach two stories, but it does not give every lot a blank check for a two-story backyard unit. The ADU must still comply with the overall maximum structure height of the underlying base zone and overlay zone.

On lots that permit single-dwelling unit development but not multiple-dwelling unit development, detached ADU structures and ADUs attached to existing accessory structures may not exceed two stories.

Why Height Is Not Just One Number

• Base zone height limits may control the maximum envelope.
• Overlay zones can add special limits or review.
• Coastal Overlay Zone projects may follow different effective rules.
• Structures over 16 feet can trigger more sensitive setback analysis.
• Fire access, slope, and building separation can affect design.

When a Two-Story ADU Makes Sense

A two-story ADU is most useful on small lots where the owner wants to preserve yard space, add bedrooms, create views, or separate living and sleeping areas. It can also help when the desired square footage is hard to fit in a one-story footprint.

The tradeoff is cost and complexity. Stairs, structural design, privacy, window placement, and fire review can make a two-story design more expensive than a compact one-story unit.

Feasibility Checklist

• Confirm the zone and overlay zone in ZAPP.
• Check whether the property is in the Coastal Overlay Zone.
• Compare the proposed height with base-zone limits.
• Check side and rear setbacks for taller ADU walls.
• Review fire access, canyon, slope, and easement constraints.

Related San Diego research: setbacks, size limits, and sprinklers.

Building in LA instead? Check out our Los Angeles ADU Guide.

Source Notes

Informational only. Not legal, architectural, engineering, or permit approval advice.