ADU Constructionin Pomona, CA
ADU construction in Pomona is approved ministerially with a building permit, and the City must act on a complete application within 60 days or it is deemed approved. A detached unit can be up to 800 square feet by right, with larger sizes tied to lot size: 850 or 1,000 square feet under 7,200 and up to 1,200 above it.
Pomona grew from a citrus belt railroad town, incorporated in 1888, into a freeway-era suburb: Interstate 10 reached it in 1954 and its population rose 89.7 percent in the 1950s to 67,157 by 1960. That history left a lot of land under single houses. The Census Bureau's 2024 estimates put about 58.5 percent of Pomona's 44,805 homes in single-family detached houses, and the city's code, rewritten in July 2024, now sets ADU size by lot size rather than one number for everyone.
This page explains how that works on a Pomona lot, where the City's wording needs a second look against state law, and what changes in a historic district. We are MDG Builders, CSLB #1040337, and we handle design, permits and supervision while licensed subcontractors pour, frame and wire the unit. Cost tables and the phase timeline are on our ADU construction page, and the Pomona overview lists our other local pages.
What Pomona's ADU code and state law say about building an ADU
Where adu construction permits come from in Pomona: City of Pomona Development Services Department, Building and Safety Division.
- Pomona's ADU section (Sec. 830.A of the 2024 Zoning and Development Code) allows with a building permit only: one interior ADU plus one junior ADU on a single-unit lot, or one new detached ADU of 800 square feet or less with side and rear setbacks of at least 4 feet. On multi-unit lots it allows interior ADUs up to 25 percent of the existing units (at least one) and no more than two detached ADUs. Review is ministerial with no hearing, and the city must approve or deny a complete application within 60 days or it is deemed approved.
- Larger Pomona ADUs (Type 2) are capped by lot size: on lots under 7,200 square feet a studio or one-bedroom unit may be up to 850 square feet and a unit with two or more bedrooms up to 1,000 square feet; on lots of 7,200 square feet or more, up to 1,200 square feet, though no front yard, coverage or open space rule may force an ADU below 800 square feet. Side and rear yards are the zone's minimum or 4 feet, whichever is less, and no parking is required for any ADU (voluntary spaces must be 9 by 18 feet).
- Height for a detached Pomona ADU is 16 feet, or 18 feet within one-half mile walking distance of a major transit stop or high-quality transit corridor or on a multifamily lot with a building over one story, and up to 20 feet to match the main house's roof pitch. An attached ADU is limited to 25 feet or the zone height, whichever is lower, and ADUs may not exceed two stories. Exterior materials and colors of Type 2 ADUs must match the main house.
- Other Pomona ADU conditions: a recorded deed restriction (no separate sale, restricted to the approved size) before the certificate of occupancy; no rental under 30 days; owner occupancy applies to JADUs only; a percolation test is required if the unit connects to an on-site septic system; fire sprinklers are required in the ADU only if the main house needs them; and parking is not replaced when a garage is demolished or converted for an ADU.
- HCD's October 29, 2024 letter reviewed Pomona's ADU Ordinance No. 4324 (adopted December 19, 2022) and found it did not comply with state law on seven points, among them a 30-day rental minimum for JADUs, an owner-occupancy requirement for ADUs, the deed restriction and a single-unit definition of primary dwelling, and gave the city until November 27, 2024 to respond. The 2024 zoning code text still shows a 30-day rental term and a deed restriction, so confirm the current wording with Planning.
- A new accessory structure at a Pomona historic resource is treated as a Major Certificate of Appropriateness item decided by the Historic Preservation Commission, and the building permit is not issued until the certificate is approved, so an ADU on a landmark or in a historic district needs that review in addition to the building permit.
Sources for these rules
How big can you build an ADU in Pomona? Caps by lot size
Section 830.A of Pomona's 2024 Zoning and Development Code, which we read on the code mirror because the City's own site blocked our tools, gives a homeowner two routes. The smaller route allows, with a building permit only, one interior ADU plus one junior ADU on a single-unit lot, or one new detached ADU of 800 square feet or less with side and rear setbacks of at least 4 feet.
The larger route sizes the unit to the lot. Under 7,200 square feet, a studio or one-bedroom ADU can reach 850 square feet and a unit with two or more bedrooms 1,000 square feet. On a lot of 7,200 square feet or more the cap is 1,200 square feet, and no front yard, coverage or open space rule may push a unit below 800 square feet.
A junior ADU, built inside the existing house, stays small under state law. Our explainer on ADU versus JADU in California compares the two, and you can read the statute's index for Government Code sections 66310 to 66342 yourself.
Ask Planning to confirm your lot's square footage from the parcel record, since a few hundred feet decides which cap applies.
Height, setbacks and apartment lots: other limits on a Pomona detached ADU
A detached ADU in Pomona is limited to 16 feet, or 18 feet within a half mile walking distance of a major transit stop or high-quality transit corridor, or on a multifamily lot with a building over one story. It may reach 20 feet to match the main house's roof pitch. An attached unit is held to 25 feet or the zone's height, whichever is lower, and no ADU may exceed two stories. Side and rear yards are the zone's minimum or 4 feet, whichever is less.
Larger units must match the main house's exterior materials and colors, so a stucco house with a tile roof gets a stucco unit with a matching roof. Voluntary parking spaces must be 9 by 18 feet, but no parking is required for any ADU.
Multi-unit lots work differently. The code allows interior ADUs up to 25 percent of the existing units, at least one, and no more than two detached ADUs. That matters in a city where about 19.5 percent of homes sit in buildings of five or more units and about 47.9 percent of households rent.
Build an ADU from a garage in Pomona: parking, walls and utilities
Converting a garage is the shortest road to a legal unit in a city of mostly detached houses. Pomona's code says parking is not replaced when a garage is demolished or converted for an ADU, and state law agrees, so the driveway can stay a driveway. Fire sprinklers are required in the ADU only if the main house needs them.
The ministerial permit covers zoning. The technical list for turning a garage into a bedroom, with a framed-in door opening, a footing and slab check, egress, smoke alarms, an energy compliance report and utilities, is the building department's. We did not read Pomona's own conversion handout, so we do not quote a wall rating, panel size or slab thickness here. Los Angeles publishes a conversion checklist, and our garage conversion permit steps post walks through that one so you know the kinds of items to ask Pomona about.
Ask Building and Safety for the conversion requirements for your address in writing, and ask whether a garage built without a permit needs an inspection record before it can be converted.
Can you build an ADU behind an older house in a Pomona historic district?
Yes, but the path is longer. A new accessory structure at a Pomona historic resource is a Major Certificate of Appropriateness item decided by the Historic Preservation Commission, and the building permit is not issued until the certificate is approved. That breaks the usual ministerial, no-hearing route for lots in Hacienda Park, Lincoln Park, Wilton Heights, Edison, Civic Center and Landmark Quarter, and for individually designated landmarks.
The housing record explains why so many lots qualify for a look. About 11.8 percent of Pomona's homes were built in 1939 or earlier, about 17.9 percent before 1950, and Lincoln Park alone has 821 structures, mostly built from the 1890s to the 1940s. An ADU there should read as a quiet backyard cottage that does not compete with the main house.
Start at the Planning Division with a parcel number, photos of the main house and a sketch of the unit's footprint and height. We did not find the City's fee or review time for the certificate, so ask both before you set a budget.
Where Pomona's ADU ordinance and state law have disagreed
In October 2024 the state Housing and Community Development department reviewed Pomona's ADU Ordinance 4324, adopted December 19, 2022, and found it did not comply with state law on seven points. Among them were a 30-day rental minimum for junior ADUs, an owner-occupancy requirement for ADUs, the deed restriction and a definition of primary dwelling limited to single-unit homes. The letter itself gave the City until November 27, 2024 to respond.
The July 2024 zoning code is a later text. It still shows a rental term of at least 30 days, a recorded deed restriction before the certificate of occupancy and owner occupancy for junior ADUs only, so we cannot tell you whether the City answered the letter by amending it. Where a city rule conflicts with state law, the statute and HCD's ADU handbook control.
A safe approach is to design to the stricter reading, then ask Planning in writing which text it applies on the day of submittal.
Septic, impact fees and the permit clock for ADU construction in Pomona
If the unit will connect to an on-site septic system, Pomona requires a percolation test; otherwise the unit ties into the sewer, and a camera inspection of the lateral before design shows what it can carry. State law bars impact fees on an ADU of 750 square feet or less, while utility connection and capacity charges are separate. The City sets its permit fees by council resolution, and we could not read that schedule, so your proposal will list the fees for your address.
State law gives the City 15 business days to say whether an application is complete and 60 days to approve or deny a complete one, after which it is deemed approved. A denial must list the defects, and an appeal gets a final answer within 60 business days.
Our planning estimate for construction is about 3 to 5 months for a garage conversion and 5 to 9 months for a detached unit. A newly built detached ADU must also carry solar panels under the Energy Code, according to HCD's handbook.
Keep every approval email and correction letter, because the 60 day clock runs from the date the application is complete, and that date can be disputed.
ADU photos from Pomona and nearby communities
Six ADU scenes tied to Pomona neighborhoods and nearby places such as La Verne, Claremont and San Dimas, from slab and framing to finished backyard units. Tap a photo to enlarge it.
What adu construction costs around Pomona
Our ADU cost table puts a garage conversion at roughly $100,000 to $200,000 and a new detached unit of 400 to 800 square feet at $200,000 to $400,000, drawn from named studies dated 2018 to 2026. Remodeling magazine's 2025 Cost vs. Value report lists $178,536 for a Los Angeles ADU, with 39.9 percent of that cost recouped at resale. We found no Pomona price study, so read these as regional ranges. The ADU cost guide explains the sources, and room addition or ADU helps you choose between them. Pomona's neighbors Claremont, La Verne and San Dimas are separate cities with their own building departments. For comparison, read how Glendale, Pasadena and Los Angeles handle ADUs. The same lot may also need a room addition in Pomona or a bathroom remodel in Pomona in the main house, and our license check guide shows how to vet any ADU builder, us included.
| What it covers | Typical range |
|---|---|
| Garage conversion to a studio or one bedroom | $100,000 to $200,000 |
| New detached ADU, 400 to 800 sq ft | $200,000 to $400,000 |
| UC Berkeley survey, Los Angeles County median, 2018 and 2019 projects | $100,000 overall. $90,000 garage. $180,000 detached. |
| Terner Center and Berkeley CCI, 2020 | $148,000 Los Angeles estimate. $167,000 statewide average. |
| Remodeling Cost vs. Value 2025, Los Angeles | $178,536 job cost |
| Electrical and plumbing, Angi Los Angeles, January 2026 | Electrical $2,600 to $7,800. plumbing $3,900 to $10,400. |
| City permit and plan check fees | Not priced here |
Pomona ADU questions, answered
How big can an ADU be in Pomona?
A detached ADU of 800 square feet or less is allowed on a single-unit lot, and larger units follow lot size. Under 7,200 square feet, a studio or one-bedroom can reach 850 square feet and a unit with two or more bedrooms 1,000 square feet. On lots of 7,200 square feet or more, the cap is 1,200. State law caps a junior ADU at 500.
Do I need to provide parking for my ADU in Pomona if I convert a garage?
No. Pomona's ADU section requires no parking for any ADU, and parking is not replaced when a garage or carport is demolished or converted. If you add voluntary spaces, each must measure 9 by 18 feet, and tandem spaces are allowed. Check the lot against your HOA rules if you have one, since private covenants are separate.
Do I have to live on the property to build or rent an ADU in Pomona?
Not for a regular ADU under state law, which does not allow an owner-occupancy rule for ADUs. The City's zoning code applies owner occupancy to junior ADUs only. HCD's 2024 letter flagged owner occupancy among Pomona's compliance problems, so ask Planning which wording applies now. Rentals cannot be shorter than 30 days.
Can I build more than one ADU on my Pomona property?
Yes, in some combinations. A single-unit lot can have one interior ADU plus one junior ADU, or one new detached ADU of 800 square feet or less. A lot with an existing multi-unit building can add interior ADUs up to 25 percent of the existing units, at least one, and no more than two detached ADUs.
How long does it take to build an ADU in Pomona and get a permit?
Expect roughly 4 to 10 weeks of design, up to 60 days of City review and 3 to 9 months of building, by our planning estimates. State law sets the review clock: 15 business days for a completeness check, then 60 days to approve or deny a complete application, after which it is deemed approved. A historic district certificate adds its own review.
How much do ADU permits and fees cost in Pomona?
We could not verify an amount, so we print none. Pomona sets permit fees by council resolution that we could not open, and the code text lists no dollar figures. State law bars impact fees on an ADU of 750 square feet or less, but sewer, water and other connection charges are separate. Ask for a fee estimate before you sign.
How much does it cost to build an ADU in Pomona?
Plan on about $100,000 to $200,000 for a garage conversion and $200,000 to $400,000 for a new detached unit of 400 to 800 square feet. These are regional ranges built from surveys and reports because we found no Pomona-specific study. Site work, utility connections and finish level move the total more than the square footage does.
Can I convert my garage to an ADU in Pomona?
Yes, and it is the common route on older single-family lots. Parking is not replaced, and a conversion of an existing structure does not need new side or rear setbacks under state law. The building department sets the technical items, such as egress, energy compliance and utilities, so ask for its conversion requirements before design starts.
Does an ADU in a Pomona historic district need extra approval?
Yes. A new accessory structure at a historic resource is a Major Certificate of Appropriateness item decided by the Historic Preservation Commission, and the building permit waits for that approval. The rule covers Pomona's six historic districts and designated landmarks. Contact the Planning Division with your parcel and photos before you commission drawings.
Can I rent my Pomona ADU on Airbnb?
Not for stays under 30 days. Pomona's code prohibits renting an ADU for fewer than 30 days, and state law allows a city to require rentals longer than 30 days. Long-term tenants fit that rule. We did not research a separate Pomona short-term rental ordinance, so ask Planning before you plan on nightly income.
Describe your Pomona ADU idea
Tell us the street, your lot size if you know it, whether you have a garage to convert and whether the house is in a historic district, and we will check the cap and overlay before the visit.