ADU in Pomona, CA
Junior ADU & Interior Conversion in Pomona typically runs $85,000-$175,000 all-in, drawings through final inspection, while ADU Site Prep & Utilities adds $25,000-$75,000 depending on whether your 1920s-era home needs a full electrical service upgrade. We’re Ellery ADU Studio, a design-build practice that has handled Pomona’s inland heat, aging housing stock, and university-driven rental demand since 2015. Call (951) 577-3472 for a free estimate with a written price before any work starts.
Why Pomona Homes Are Different
Pomona sits in an inland valley with zero marine influence, making it one of Los Angeles County’s hottest cities. Triple-digit days in July and August are routine, and recorded heat events exceed anything coastal LA sees. ADU builds here need heavier HVAC tonnage and tighter wall insulation than most LA Basin projects. Detached ADUs with significant west- or south-facing glass require shading or low-e glazing specified from the start.
The housing stock is equally distinctive. Pomona’s residential fabric is heavily 1920s-1950s Craftsman bungalows and postwar ranch homes on 6,000-9,000 sq ft parcels, large enough that many owners clear state and local setback minimums without a variance. Detached single-car garages from this era are common and prime conversion candidates, though their slabs frequently need reinforcement and knob-and-tube or early-Romex wiring requires full replacement before inspection sign-off.
A large share of older homes still run on 100A or even original 60A service panels. When a homeowner greenlights a garage conversion ADU, contractors routinely discover the main panel has no capacity headroom, forcing a full 200A service upgrade and new subpanel before the ADU electrical rough-in can begin. Experienced local ADU builders now build panel upgrades into baseline bids rather than treating them as change orders.
Pomona’s proximity to Cal Poly Pomona and the Claremont Colleges creates concentrated near-campus rental demand. Large-lot 1920s-1950s housing gives homeowners rear-yard depth to build detached ADUs that rent to students and university employees at ROI unmatched in pricier neighboring cities like Claremont or La Verne.
Our Main Pomona Services
Most Pomona homeowners start with one of these three core services, each with its own dedicated page and local pricing.
ADU Design & Permitting in Pomona
Our permit set is the core product, not an afterthought. In Pomona, this means navigating the city’s specific setback rules for 1920s-era lots and documenting how your existing structure meets or exceeds current code. We handle the full architectural drawings, structural calculations, and energy compliance documentation required for Pomona plan check. ADU Design & Permitting in Pomona covers every step from measured drawings to approved permit.
Garage Conversion ADU in Pomona
Pomona’s detached single-car garages from the 1920s-1950s are prime conversion candidates, though slab reinforcement and full electrical rewiring are common prerequisites. We assess foundation capacity, roof structure, and utility routing before quoting, so the written price accounts for real conditions, not optimistic assumptions. Garage Conversion ADU in Pomona details the full process.
New Detached ADU in Pomona
With 6,000-9,000 sq ft parcels common in Pomona, many owners clear setback minimums without a variance, making detached ADUs straightforward on paper. The inland heat demands heavier HVAC and tighter insulation than coastal builds, and west- or south-facing glass needs shading or low-e glazing from the start. New Detached ADU in Pomona breaks down the full scope and pricing.
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
Junior ADU & Interior Conversion in Pomona converts existing interior space into permitted rental units, ideal for homeowners whose 1920s-1950s homes have underutilized basements, attics, or attached rooms but lack the budget or yard space for detached construction. The university rental market here means a finished Junior ADU can cash-flow within months, not years. Junior ADU & Interior Conversion covers our full service across Southern California.
Basement ADU
Signs you need it
Your basement has 7+ feet of clearance, existing egress windows, and you’re tired of using it for storage while Pomona rental rates climb.
What it costs in Pomona
Basement ADU conversions in Pomona typically run $85,000-$140,000 all-in, including moisture mitigation, egress compliance, and full mechanical systems.
How we do it
We measure existing conditions, design the layout to meet Pomona’s light and ventilation requirements, produce the full permit set, and build to the drawings with a documented photo record at every visit.
Room-to-ADU Conversion
Signs you need it
You have an attached bedroom, den, or in-law space with separate exterior access and want legal rental income without adding square footage.
What it costs in Pomona
Room-to-ADU conversions in Pomona typically run $75,000-$125,000, depending on whether the existing space needs kitchenette plumbing and separate metering.
How we do it
We verify the space meets Junior ADU size limits, design the kitchenette and bathroom layout, prepare the full permit set for Pomona plan check, and construct to the approved drawings under our single contract.
What Junior ADU & Interior Conversion Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Basement ADU conversion | $85,000 - $140,000 |
| Room-to-ADU conversion | $75,000 - $125,000 |
| Above-garage ADU (interior only) | $95,000 - $175,000 |
Does a Junior ADU need its own meter in Pomona?
No, California state law allows Junior ADUs to share electrical and water service with the primary residence, though separate metering is optional and may improve rental appeal near Cal Poly Pomona. Call (951) 577-3472 for an exact quote - estimates are free.
Can I convert any room into a Junior ADU?
The space must be within the existing walls of your home, have exterior access, and meet Pomona’s ceiling height and ventilation codes; attached garages and basements each have additional requirements. Call (951) 577-3472 for an exact quote - estimates are free.
ADU Site Prep & Utilities in Pomona
ADU Site Prep & Utilities in Pomona addresses the hidden infrastructure work that must complete before framing begins, especially critical given the city’s aging housing stock and inland heat. Many Pomona homes still run on 100A or even 60A panels, and contractors who don’t build electrical upgrades into baseline bids hit homeowners with change orders mid-project. ADU Site Prep & Utilities details our full infrastructure service.
Electrical Panel Upgrade
Signs you need it
Your main panel is rated 100A or less, has no open breaker slots, or still contains original fuses from the 1950s.
What it costs in Pomona
Electrical panel upgrades in Pomona typically run $8,000-$18,000, including the new 200A service, subpanel, and coordination with Southern California Edison.
How we do it
We verify existing load calculations, specify the new 200A service and subpanel, pull the permit, and coordinate SCE inspection before the ADU rough-in begins.
Foundation & Grading
Signs you need it
Your garage slab is cracked, under 4 inches thick, or sloped toward the house, or your rear yard needs cut-and-fill for a detached ADU pad.
What it costs in Pomona
Foundation and grading work in Pomona typically runs $12,000-$35,000, depending on soil conditions and whether the existing slab requires full replacement.
How we do it
We test soil bearing capacity, design the pad or reinforcement to Pomona’s seismic and drainage requirements, and pour to the engineered spec with photo documentation at each phase.
What ADU Site Prep & Utilities Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Electrical panel upgrade | $8,000 - $18,000 |
| Foundation & grading | $12,000 - $35,000 |
| Plumbing lateral extension | $5,000 - $15,000 |
Is the electrical upgrade included in the ADU price?
We itemize it separately so you see exactly what the infrastructure costs, but it’s quoted upfront in writing before any work starts, not discovered mid-project. Call (951) 577-3472 for an exact quote - estimates are free.
How long does site prep take before construction starts?
Electrical and foundation work typically requires 3-6 weeks including permit and inspection scheduling in Pomona; we sequence it so framing begins immediately after final utility inspection. Call (951) 577-3472 for an exact quote - estimates are free.
Brands We Service in Pomona
We specify and coordinate prefab and modular systems from Abodu, Cover, and James Hardie within our single-contract model, sourcing components through regional distributors with typical turnaround of 4-8 weeks for standard configurations. See our brands for the full list.
Pricing for ADU in Pomona, CA
| Service | Typical range in Pomona |
|---|---|
| Basement ADU conversion | $85,000 - $140,000 |
| Room-to-ADU conversion | $75,000 - $125,000 |
| Above-garage ADU (interior) | $95,000 - $175,000 |
| Electrical panel upgrade | $8,000 - $18,000 |
| Foundation & grading | $12,000 - $35,000 |
| Plumbing lateral extension | $5,000 - $15,000 |
| Garage conversion ADU (full) | $120,000 - $220,000 |
| New detached ADU (full) | $250,000 - $450,000 |
Prices in Pomona push higher when existing slabs need full replacement, when 60A or 100A panels require upgrading, or when inland heat loads demand oversized HVAC and enhanced wall insulation. 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 varied residential districts, from the historic Lincoln Park area to the postwar tracts near Ganesha Hills. Crews are dispatched from our Los Angeles office and typically arrive within 45 minutes to scheduled appointments anywhere in the city.
- Lincoln Park
- Ganesha Hills
- Mayflower Village
- Philadelphia Square
- Downtown Pomona
Service Area - Cities Near Pomona
Our crews serve the full Pomona Valley and western San Gabriel Valley, including Diamond Bar, CA to the south, Montclair, CA to the east, Chino Hills, CA to the southeast, and Claremont, CA immediately to the west. Each city has distinct setback rules, utility coordination requirements, and rental market conditions that we factor into every written quote.
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 processes ADU permits through the standard plan check queue, typically 6-10 weeks for a complete submittal; our permit set includes all structural, energy, and fire-safety documentation to avoid resubmittal delays. We track every submittal and respond to corrections within 48 hours.
California law limits HOA prohibition of ADUs, but some Pomona neighborhoods with active associations impose design guidelines on exterior materials and rooflines; we review CC&Rs during our initial site visit and flag any compliance requirements in the written scope.
Pomona’s northern and eastern edges include sloped terrain that triggers additional grading and drainage requirements; we conduct geotechnical assessment as part of site prep and engineer foundations to the specific slope and soil conditions, all itemized in the upfront quote.
Call (951) 577-3472 to schedule your free estimate. Every project receives a written price before any work starts, a documented photo record on every visit, and our 365-Day Done Right Promise backed in writing.
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
"The rental income has covered the payment since the second month. They were realistic about the numbers rather than optimistic."
- Odette N."Handled the whole planning process. We went to one hearing and that was it."
- Rowena C."Detached unit in the back garden. Good design, good build quality, and the cost changes were documented and agreed in advance."
- Stefan B.