How United Build Partners helps Alhambra homeowners
We're not a construction company. United Build Partners is an ADU advisory and contractor-matching service: we start with a free review of your property and goals, help you understand what's realistic for your lot under Alhambra's rules, and — when it's a good fit — connect you with up to three contractors in our network suited to your project type and neighborhood. From there, you compare proposals and decide who to work with; the licensed contractor you choose handles the actual design and construction.
ADU rules and permitting in Alhambra
Every ADU in California starts from the same statewide floor: ministerial (by-right) approval, at least 16 feet of height, 4-foot side and rear setbacks, and size minimums the city can't undercut. Alhambra's local rules mostly turn on one size threshold. Here's what stands out.
What's specific to Alhambra
- An 800 sq ft ADU sidesteps the zone's limits. Alhambra's key rule: an ADU of 800 square feet or less with 4-foot setbacks is exempt from the underlying zone's floor-area, lot-coverage, and open-space maximums. On a tight lot where those limits would otherwise bind, keeping the unit at or under 800 sq ft is often the move.
- Standard 4-foot setbacks. A new attached or detached ADU needs at least a four-foot side and rear yard setback — the state standard, so most lots work without a variance.
- One ADU and one JADU per single-family lot. On a residential lot with no more than one single-family structure, you can have one ADU and one JADU — the common state-law pattern.
- Multi-family lots have their own detached caps. A detached ADU on a lot with a multi-unit dwelling is capped at 850 sq ft (one bedroom or less) or 1,000 sq ft (more than one bedroom).
- Independent access and full facilities required. Every ADU needs its own entrance separate from the main home, plus a living/sleeping area, a kitchen or kitchenette (stove or hotplate, refrigerator, sink), and a bathroom with a shower or tub — the baseline that makes it a legal dwelling.
- Submit through the online Permit Portal. Alhambra takes ADU permit applications through its online Permit Portal via the Building Division, and publishes a current ADU Informational Handout (updated December 2025) — work from the latest version, not an older summary.
Property and lot considerations
Alhambra is a dense San Gabriel Valley city of mostly modest single-family lots, where floor-area, lot-coverage, and open-space limits can bind quickly on a larger build. That's exactly why the 800-square-foot exemption matters so much here — a compact unit avoids those constraints entirely. A free property review is the fastest way to see whether staying at or under 800 sq ft makes sense for your parcel; our size & setback calculator is a good first check.
Common ADU types for Alhambra homeowners
Detached ADUs, attached ADUs, and junior ADUs (JADUs) are all recognized in Alhambra. On a tight lot, a compact detached unit at or under 800 sq ft — clear of the zone's development-standard limits — is frequently the cleanest path; a JADU inside the home is simpler still. Our which-ADU quiz helps weigh the options for your lot.
Cost factors in Alhambra
The main Alhambra-specific budget lever is the 800-square-foot threshold: staying at or under it keeps you clear of the underlying zone's floor-area, lot-coverage, and open-space standards, which can otherwise force a smaller or more complicated design. None of this sets a dollar figure — our cost guide and soft-costs guide frame the full budget.
Financing your Alhambra ADU
Most homeowners fund ADU construction through a HELOC, cash-out refinance, a construction loan, or some combination — see our ADU financing overview and loan payment calculator for how each works. Financing options aren't generally city-specific, but a lender may consider your neighborhood and local rents when evaluating projected rental income as qualifying income.
How our process works
Frequently asked questions
An ADU of 800 square feet or less with 4-foot setbacks is exempt from the underlying zone's floor-area, lot-coverage, and open-space maximums. Above 800 sq ft, those zone standards apply, which can constrain a larger unit on a tight lot. Confirm your zone's limits with Planning before designing bigger.
On a single-family lot with no more than one existing or proposed single-family structure, you can build one ADU and one junior ADU. Multi-family lots follow different rules, including detached-ADU size caps of 850 sq ft (one bedroom or less) or 1,000 sq ft (more than one bedroom).
ADU permit applications go through Alhambra's online Permit Portal via the Building Division, where you'll submit for plan check. The city publishes a current ADU Informational Handout (updated December 2025) with the requirements and review process — start from that and a free property review to confirm what your lot supports.