How United Build Partners helps Downey homeowners
We're an ADU advisory and contractor-matching service, not the construction company. We start with a free review of your Downey property and goals, help you understand what the city's pre-approved plan program and height rules mean for your lot, and — when it's a good fit — connect you with up to three contractors in our network.
ADU rules and permitting in Downey
Downey's ADU standards build on the same statewide floor every California city follows — ministerial review and a 60-day clock on complete applications (see our California ADU laws guide). Downey also runs a genuine pre-approved standard plans program for detached ADUs, intended to speed up the permitting process for homeowners who use one of the pre-vetted designs.
What's specific to Downey
- No two-story ADUs: Downey does not allow two-story ADUs at all — a detached ADU is capped at 16 feet, and even an attached ADU (which can rise to the height of the main structure, up to 25 feet) remains a single story in practice.
- Pre-approved plans: the city's Building Safety Division offers pre-approved standard plans for detached ADUs, designed to speed up permit review versus a fully custom design.
- Owner-occupancy: a standard ADU built after January 1, 2020 but before January 1, 2025 was generally not subject to any owner-occupancy requirement; a Junior ADU remains subject to owner-occupancy regardless of when it was built. Confirm the current requirement for your specific project timeline with the city, since state law's owner-occupancy rules for standard ADUs have changed over time.
- Unit allowance: single-family lots may generally add 1 ADU and 1 Junior ADU; multi-family lots may generally add 2 new detached ADUs plus at least 1 conversion ADU.
- Setbacks: a minimum of 4 feet side and rear for a detached ADU; no minimum setback for garage conversions or JADUs unless needed for fire safety.
Property and lot considerations
Because Downey doesn't allow a two-story ADU, homeowners here can't add square footage by building up the way they could in some neighboring cities — the practical way to maximize space is a full-footprint single-story detached ADU or an attached addition. Whether a pre-approved plan fits your lot as-is, or you'll need a custom design, depends on your specific property — a property review can help you figure out which path makes sense.
Common ADU types for Downey homeowners
Homeowners drawn to Downey's pre-approved plan program often choose a detached ADU to take advantage of the faster permitting path. Homeowners with an existing garage often consider a garage conversion instead, which isn't subject to the same setback requirements. A Junior ADU remains the lowest-cost path for converting existing interior space, though it does carry an owner-occupancy requirement.
Cost factors in Downey
Construction costs in Downey generally track the same range as the rest of our Los Angeles County service area — see our full ADU cost guide. A pre-approved plan can reduce design costs and permitting time compared with a fully custom design, though the underlying construction cost per square foot is generally similar either way.
Financing your Downey ADU
Most homeowners fund construction through a HELOC, cash-out refinance, or dedicated construction loan — see our ADU financing overview for how each works.
Rental income and property value in Downey
Downey's established single-family neighborhoods support real rental demand for many homeowners, though actual achievable rent depends heavily on your specific neighborhood and unit — we don't have a verified, current rent figure to quote. See our ADU rental income guide and ROI calculator to work through your own numbers.
How our process works
Frequently asked questions
No — Downey does not allow two-story ADUs. A detached ADU is capped at 16 feet, and even an attached ADU that can rise to the height of the main structure remains single-story in practice.
Yes — the city's Building Safety Division offers a pre-approved standard plans program specifically for detached ADUs, designed to speed up the permitting process compared to a fully custom design.
A Junior ADU carries an owner-occupancy requirement. A standard ADU built after January 1, 2020 and before January 1, 2025 generally did not require owner-occupancy — confirm the current requirement for your project timeline with the city, since this has changed under state law over time.