ADU

ADU Information Guide

What California now allows, which type fits your property, and what actually drives the cost.

The Regulatory Picture

California has significantly expanded ADU rights over the past several years. In most residential zones, ADUs are now permitted by right, with streamlined review timelines and reduced or eliminated parking requirements.

Local jurisdictions still apply their own standards for setbacks, height, and design within the limits state law allows. This is why feasibility has to be checked against your specific parcel, not a general rule.

Rules continue to evolve. Anything you read about ADU law, including this page, should be verified against current requirements for your jurisdiction before you make decisions.

The Four Types

Detached ADU. A separate structure in the rear or side yard. Most privacy and typically the highest rent, but also the highest cost since it requires new foundation, utilities, and full envelope.

Attached ADU. Built onto the existing home. Shares a wall and often utility runs, which can reduce cost relative to detached.

Garage conversion. Converts existing enclosed space. Often the lowest cost path since the shell exists, though it usually requires foundation work, insulation, and egress upgrades to meet dwelling standards.

Junior ADU (JADU). Up to 500 square feet created within the existing home footprint, typically with an efficiency kitchen. Lowest cost, most limited.

What Drives ADU Cost

Utilities. Whether you can share the existing service or need separate meters and new runs is frequently the single largest cost variable.

Site work. Sloped lots, poor access, and drainage requirements add cost quickly, particularly on hillside properties.

Foundation. New detached construction requires new foundation. Garage conversions often require foundation upgrades to meet dwelling requirements.

Finish level. A rental-grade finish and a high-end finish differ substantially in cost for the same footprint.

Before You Commit

Verify what your specific lot allows before paying for design. Setbacks, lot coverage, and height limits determine what is buildable, and those vary by jurisdiction and zone.

We provide ADU feasibility review as part of preconstruction. Learn more about our ADU construction service.

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