ADU Contractors and Builders in San Diego

Choosing an ADU contractor is one of the biggest calls in your project. This page explains how to compare ADU contractors and builders in San Diego so you can judge construction quotes side by side. We do not rate or rank builders, and we have not checked the work of any company. If we ever show featured builders here, those spots will be paid and clearly labeled.

Types of ADU contractors

• Design-build firms handle design, permits, and construction under one contract.
• General contractors build from plans you bring, often from an architect or a preapproved plan.
• Prefab companies build the unit in a factory. Many rely on a local contractor for site work and installation, which can add a lot to the price [1]. See our prefab ADU guide.

What a full quote should include

Compare quotes only when they cover the same scope. A complete ADU quote should spell out:

1. Design and engineering, or the cost to license a preapproved plan.
2. Permit, plan check, inspection, impact, and school fees, or who pays them.
3. Site prep, grading, and foundation.
4. Utility lines and hookups for water, sewer, power, and gas.
5. The unit itself, with finishes and appliances listed.
6. Final connections, cleanup, and landscaping.

For prefab ADUs, items outside the unit price can add $65,000 to $160,000, according to Block Renovation [1]. A low sticker price without these items is not a full quote.

Questions to ask every contractor

• How many ADUs have you finished in my city?
• Who submits and manages the permit?
• Can we use a preapproved plan? In the City of San Diego, preapproved plans get a 30-day review [2].
• What is your timeline from signing to move-in? One San Diego builder reports 12 to 24 months for detached ADUs from first idea to completion [3].
• How do payments work, and what happens if costs change?
• Is my lot in a coastal zone or fire hazard area, and how does that change the design [2]?

Check before you sign

• Look up the contractor's license with the California Contractors State License Board.
• Ask for proof of insurance and confirm it yourself.
• Ask for addresses of finished ADUs and talk to past clients.
• Read the contract and payment schedule carefully.

Be careful with anyone offering to get you a state ADU grant. CalHFA says its ADU grant funding was fully allocated as of December 28, 2023, and that anyone offering grant help is running a scam [4].

Get quotes

Send one short request and an independent contractor who serves your area may contact you. Request a quote.

A referral is not an endorsement, so check any contractor yourself before you sign.

We're a referral service, not a contractor, and independent contractors may pay us for referrals.

Sources

1. Block Renovation, "Prefab ADUs: What is the True Cost Savings," February 4, 2026 (updated June 17, 2026). Fetched 2026-11-11. https://www.blockrenovation.com/guides/prefab-adus-what-is-the-true-cost-savings
2. City of San Diego Development Services, "Information Bulletin 400: Accessory Dwelling Unit/Junior Accessory Dwelling Unit," January 2026. Fetched 2026-11-11. https://www.sandiego.gov/development-services/forms-publications/information-bulletins/400
3. SnapADU, "The State of Detached ADUs in San Diego (2026)," no date shown. Fetched 2026-11-11. https://snapadu.com/lessons-from-100-adu-builds-detached-adu-report-san-diego/
4. CalHFA, "ADU Grant Program," status notice dated December 28, 2023. Fetched 2026-11-11. https://www.calhfa.ca.gov/adu/