ADU in Pomona, CA
Junior ADU & Interior Conversion in Pomona typically runs $85,000-$165,000 all-in, while ADU Site Prep & Utilities adds $25,000-$75,000 before the structure begins. Most Pomona homeowners call us at (657) 286-7915 after discovering their 1960s ranch needs full infrastructure upgrades their neighbor’s newer Chino Hills home never faced. We’re Ellery ADU Studio, a design-build practice that handles drawings, permits, and construction under one written contract at one written price.
Why Pomona Homes Are Different
Pomona’s post-WWII housing stock sits on some of LA County’s largest remaining single-family lots, many 7,000-9,000 square feet with detached rear garages accessed by back alleys. These 1945-1972 stucco ranches and bungalows carry the hidden costs of age: 60-100 amp electrical service, galvanized supply lines corroded by hard water, and clay or cast-iron sewer laterals that inspectors flag during permitting.
The Pomona Valley’s inland thermal pocket pushes summer temperatures to 100-107°F, with Santa Ana wind events that degrade asphalt shingles and stucco coatings faster than coastal cities. Ductless mini-split HVAC isn’t optional here. And those alley-access neighborhoods create their own complication: utility connections often sit in ambiguous easement territory, requiring city verification that adds 2-4 weeks to projects that front-loaded cities never face.
Our Main Pomona Services
Three ADU services have dedicated Pomona pages with full pricing and local permit guidance:
ADU Design & Permitting in Pomona
We produce permit-ready construction documents calibrated to Pomona’s Planning and Community Development counter, including Title 24 energy calculations and structural packages for the city’s seismic zone. Every set includes the documentation the city requires for alley-access utility verification. ADU Design & Permitting in Pomona covers our full process, from as-built survey through certificate of occupancy.
Garage Conversion ADU in Pomona
Pomona’s detached rear garages offer excellent privacy separation from the main house, but most need foundation assessment, envelope repair from heat degradation, and full electrical service upgrades before conversion. We quote the complete scope, not just the finish work. See Garage Conversion ADU in Pomona for typical costs and timeline.
New Detached ADU in Pomona
Large lots and alley access make new detached units viable across Pomona, though setback verification and utility trenching through rear easements complicate siting. We coordinate prefab systems from brands including Plant Prefab and Abodu within our single-contract model. Details are at New Detached ADU in Pomona.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Junior ADU & Interior Conversion in Pomona
Pomona’s multigenerational households and Cal Poly Pomona’s 27,000+ student population create dual demand for Junior ADU & Interior Conversion: family-driven aging-in-place and investor-driven rental income. These projects convert existing conditioned space rather than building new, but Pomona’s aged infrastructure means even interior work often requires electrical panel upgrades and plumbing repiping before the first wall opens. Our Junior ADU & Interior Conversion hub covers standards across all our markets.
Room-to-ADU Conversion
Signs you need it
A permanently spare bedroom, den, or former rental room with separate exterior access and a ceiling height of at least 7 feet 6 inches.
What it costs in Pomona
Room-to-ADU conversions in Pomona typically run $85,000-$140,000 all-in, including the panel upgrade and mini-split HVAC that most 1960s homes require.
How we do it
We verify the existing slab and framing capacity, produce a permit set with Title 24 compliance, then execute the kitchenette, bath, and separate meter work under our single contract.
Interior JADU
Signs you need it
Owner-occupancy of the main house is required, and you want a 500-square-foot-max unit inside the existing footprint with shared utilities.
What it costs in Pomona
Interior JADUs in Pomona typically run $75,000-$125,000, lower than standalone ADUs because they share electrical and water service, though galvanized pipe replacement often still applies.
How we do it
We document the existing conditions, design to the JADU code chapter’s owner-occupancy requirement, permit through Pomona’s counter, and build to the documented photo record standard.
What Junior ADU & Interior Conversion Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Room-to-ADU conversion (all-in) | $85,000-$140,000 |
| Interior JADU (all-in) | $75,000-$125,000 |
| Electrical panel upgrade (if needed) | $8,000-$18,000 |
Does a Junior ADU need its own meter in Pomona?
No. Junior ADUs share utilities with the main house per California code, though we often recommend sub-metering for rental clarity. Call (657) 286-7915 to discuss your specific layout and whether sub-metering fits your plan.
Can I convert any room, or does Pomona require specific access?
The space needs a separate exterior door and direct outside access; interior-only access through the main house does not qualify. We assess this during our first site visit and document it in your permit set.
ADU Site Prep & Utilities in Pomona
Pomona’s infrastructure age makes Site Prep & Utilities a defining line item on nearly every ADU project we take here. Galvanized pipes, undersized panels, and clay sewer laterals aren’t exceptions; they’re the norm in 1950s-60s neighborhoods. Our ADU Site Prep & Utilities hub details how we coordinate these trades within our single-contract model, eliminating the designer-versus-builder blame gap that derails most projects.
Electrical Panel Upgrade
Signs you need it
A 60-100 amp Zinsco, Federal Pacific, or original panel with no spare breaker spaces and visible corrosion on the feeder cables.
What it costs in Pomona
Electrical panel upgrades in Pomona typically run $8,000-$18,000, including trenching to the alley-access meter location that many homes require.
How we do it
We pull the permit with SCE coordination, upgrade to 200-amp service with grounded bus, and photograph every connection for your documented record.
Plumbing Lateral
Signs you need it
Galvanized supply lines with reduced flow, visible corrosion at fittings, or clay/cast-iron sewer laterals that fail camera inspection.
What it costs in Pomona
Plumbing lateral replacement in Pomona typically runs $12,000-$28,000, higher than neighboring cities due to hard-water corrosion and alley-access trenching complications.
How we do it
We camera the line, permit through Pomona’s building division, trench or trenchlessly replace to city main, and pressure-test before backfill.
What ADU Site Prep & Utilities Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Electrical panel upgrade | $8,000-$18,000 |
| Plumbing lateral replacement | $12,000-$28,000 |
| Foundation repair/prep for conversion | $5,000-$15,000 |
Will Pomona let me trench the alley without city approval?
No. Alley utility easements require explicit verification from Pomona’s Public Works department before we cut pavement or disturb underground infrastructure. We handle this coordination as part of our permit phase.
Can Site Prep be done under a separate contract?
No. Under our design-build model, Site Prep & Utilities is integrated into your single written contract with one price, preventing the change-order disputes that split-contract projects generate. Call (657) 286-7915 for a scope review.
Brands We Service in Pomona
We specify and coordinate prefab and modular systems from Plant Prefab, Tuff Shed, and James Hardie within our single-contract model, with parts and expertise stocked for local turnaround. See our brands for full compatibility details.
Pricing for ADU in Pomona, CA
| Service | Typical range in Pomona |
|---|---|
| Room-to-ADU conversion | $85,000-$140,000 |
| Interior JADU | $75,000-$125,000 |
| Electrical panel upgrade | $8,000-$18,000 |
| Plumbing lateral replacement | $12,000-$28,000 |
| Foundation repair/prep | $5,000-$15,000 |
| Above-Garage ADU | $110,000-$185,000 |
| Basement ADU | $95,000-$160,000 |
| Gas line extension | $3,500-$9,000 |
Prices in Pomona push higher when alley-access utility verification extends timelines, when Santa Ana wind damage requires envelope repair, or when hard-water corrosion demands full repiping rather than spot repair. Every project is quoted with a written price before any work begins, per Haven Standard Clause 1.
Neighborhoods We Serve in Pomona
We work across Pomona’s full footprint, from the older post-war neighborhoods near downtown to the ranch-style tracts toward the northern hills. Crews are dispatched from our Los Angeles office and typically schedule initial site visits within the metro response window.
- Lincoln Park
- Mayfair
- Westmont
- Philips Ranch
- Downtown Pomona
Service Area - Cities Near Pomona
Our crews serve homeowners throughout the eastern San Gabriel Valley and western Inland Empire, including Diamond Bar, CA, Montclair, CA, Chino Hills, CA, and San Dimas, CA. Each city has distinct permit timelines, utility coordination requirements, and housing-stock conditions that we calibrate for in our site assessments.
Serving Pomona, CA - Our Local Coverage Area
We’re based in the Pomona area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About ADU in Pomona
Pomona’s Planning and Community Development department typically reviews complete ADU permit sets in 8-12 weeks, though alley-access utility verification can add 2-4 weeks before submission. We front-load this coordination so it runs parallel to drawing production, not after.
Yes. California’s JADU code requires owner-occupancy of either the main house or the Junior ADU, and Pomona enforces this at permit issuance and through periodic verification. We document this requirement in your permit set and contract.
We can review any complete permit set for a Free Second Opinion, but our design-build contract requires that we stand behind the drawings we produce. If your architect’s set is incomplete or misses Pomona-specific requirements like alley easement notation, we’ll quote the revision scope under our standard written pricing.
Call (657) 286-7915 to schedule your free estimate. A live person answers 24/7.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Pomona Customers Say
"Every allowance was itemised at the start, so the finish selections did not turn into a surprise at the end."
- Benedict H."Garage conversion finished on the drawings and close to the schedule. They were honest that the sewer connection was the unknown, and it was."
- Arjun D."The rental income has covered the payment since the second month. They were realistic about the numbers rather than optimistic."
- Odette N.