ADU Rules in Hidden Hills.
Local ADU regulations, permit fees, setback requirements, and typical timelines for Hidden Hills. Last updated 2026-05-27.
Hidden Hills ADU Requirements
Attached ADU: up to 25 ft
No transit access; replacement parking required.
Design 6 weeks · Permit 8 weeks · Build 40 weeks
Plain-language summary
In Hidden Hills, a detached ADU requires a minimum 4-foot side setback and 4-foot rear setback. The maximum height for a detached ADU is 16 feet, while an attached ADU may be up to 25 feet. The maximum size for a detached ADU is 1,200 sq ft; a Junior ADU (JADU) is limited to 500 sq ft. Replacement parking is required for most projects. Typical permit fees range from $10,000 to $20,000. A typical project takes approximately ~13 months from design start to move-in, including 6 weeks of design, 8 weeks for permit review, and 40 weeks of construction.
⚠️ ADU rules change frequently. Always verify current requirements with the Hidden Hills Building & Safety Department before submitting plans. Official source →
What to Watch Out For
- Hidden Hills is an entirely gated, private city — all streets and common areas are owned by the Hidden Hills Community Association (HHCA).
- HHCA approval is required before any permit submittal; design review and association fees apply.
- Equestrian zoning throughout: ADU placement must avoid horse trail easements and maintain equestrian access.
- VHFHSZ designation applies; fire-resistant construction required.
- Las Virgenes Municipal Water District (LVMD) connection fees apply.
How Long Does It Take to Get an ADU Permit in Hidden Hills?
Site study, floor plans, elevations, structural drawings.
Plan check, corrections, and permit issuance by Hidden Hills Building & Safety.
Foundation, framing, MEP rough-in, finishes, final inspection.
A licensed engineer on your lot, free.
30 minutes. We walk the property, figure out what's feasible, and answer any questions you have.
We're booking out further than usual. Click Book my free visit to see all available times.
Explore all of our services.
One accountable team for every step of your ADU project — from initial sketches and city permits to financing, construction, and legalization.
ADU Design
Our ADU design team works closely with each client to create adaptable layouts that fit your site, lifestyle, and goals.
Learn more →ADU Building Permits
We manage every ADU building permit, drawing, document, and approval with your city and county — start to finish.
Learn more →Legalizing Unpermitted ADUs
We help you navigate the legalization process for your existing ADU, ensuring compliance and securing permits.
Learn more →ADU Construction
We oversee the full construction process with care, skill, and clear communication, turning your plan into a beautiful ADU.
Learn more →Modular ADUs
Save money and build faster with a modular ADU. Factory-built, site-installed, and ready in months — not years.
Learn more →ADU Financing
We work with multiple ADU-specific lenders so you can find the right financing — HEA, HEI, HELOC, or construction-to-perm.
Learn more →