ADU in Pomona, CA
Junior ADU and interior conversion in Pomona typically runs $85,000-$155,000 all-in, drawings through final inspection, while site prep and utility work adds $18,000-$65,000 depending on whether your 1920s-era home needs a panel upgrade or sewer lateral replacement. We’re Ellery ADU Studio, and we handle both the permit set and the build under one contract at one written price. Call (909) 323-1107 to schedule your free estimate.
Most Pomona homeowners come to us with two problems: an aging parent who needs to stay close, or a garage or basement sitting empty while Cal Poly Pomona rents climb 8% year over year. Our Junior ADU & Interior Conversion service turns existing square footage into permitted rental income or multigenerational housing without expanding the building footprint. The city’s stock of pre-WWII detached garages and unpermitted casitas makes Pomona’s ADU economics unusually strong, but only if the permit set is done right the first time.
Why Pomona Homes Are Different
Pomona’s housing was built in two waves: Craftsman bungalows and Spanish Colonial Revival homes from the 1920s through 1950s, concentrated in north Pomona and the Lincoln Park corridor, with later ranch infill. These original detached garages sit on 7,000-10,000+ sq ft lots, structurally ready for conversion but electrically unprepared. Most still run 60- or 100-amp service that cannot handle an ADU load without a panel upgrade.
The inland valley climate pushes summer highs past 100°F regularly, measurably hotter than coastal LA. Mini-split sizing and insulation R-values that work in Pasadena fail here. We’ve seen contractors specify 9,000 BTU units for Pomona garage conversions that need 18,000 BTU minimum.
Pomona also carries an unusual legacy: unpermitted casitas built in the 1970s and 1980s for extended family. When owners try to legalize these, Development Services often finds encroachment on the 4-foot side setback now required. A survey and minor variance add time and cost that newer cities simply don’t face.
Our Main Pomona Services
Most Pomona homeowners start with one of these three project types before adding site prep and utilities.
ADU Design & Permitting in Pomona
We produce the full permit set, structural calculations, and Title 24 energy compliance for Pomona’s Development Services counter. Because we also build what we draw, our plans include construction-phase notes that prevent the redesign loops common when architects and contractors blame each other. ADU Design & Permitting in Pomona covers feasibility studies, existing conditions surveys, and variance applications for setback issues.
Garage Conversion ADU in Pomona
Our most frequent Pomona project: converting a pre-WWII detached garage into a permitted studio or one-bedroom. We assess slab thickness, stem-wall condition, and electrical service before quoting. Most need panel upgrades and radiant-heat insulation that coastal contractors undersize. Garage Conversion ADU in Pomona includes the full build from drawings to final inspection.
New Detached ADU in Pomona
When the existing garage is too far gone or the lot allows a better placement, we design and build a new detached unit. We coordinate prefab systems from Plant Prefab or Tuff Shed when the timeline demands it, or stick-build with James Hardie siding for custom matching. New Detached ADU in Pomona includes foundation, utilities, and finish under one contract.
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.
Before
AfterJunior ADU & Interior Conversion in Pomona
Junior ADU and interior conversion in Pomona solves a specific problem: turning existing space into independent living without the cost of new construction. The city’s older housing stock, large lots, and dual demand from student renters and multigenerational families make this the highest-ROI ADU type here. We handle the full Junior ADU & Interior Conversion process, including the HCD checklist and Pomona’s fire-separation requirements for attached units.
Room-to-ADU Conversion
Signs you need it
You have a ground-floor bedroom or den with exterior access, a separate entrance is possible without structural changes, and the main home has space to spare.
What it costs in Pomona
Room-to-ADU conversion in Pomona typically runs $85,000-$125,000 including the kitchenette, bathroom, permit set, and fire separation.
How we do it
We survey existing conditions, design the separation wall to Pomona’s one-hour fire rating, produce the HCD-compliant permit set, and build through final inspection with a documented photo record at each visit.
Interior JADU
Signs you need it
You need a compact independent unit inside your main home, you are willing to share utility meters, and the owner-occupancy requirement works for your situation.
What it costs in Pomona
Interior JADU in Pomona typically runs $65,000-$95,000 including the efficiency kitchen, 3/4 bath, and permit compliance.
How we do it
We verify the 500-square-foot maximum, design the efficiency kitchen layout to code, handle Pomona’s owner-occupancy affidavit, and deliver a permitted unit with locked written pricing under Haven Standard Clause 1.
What Junior ADU & Interior Conversion Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Room-to-ADU conversion | $85,000-$125,000 |
| Interior JADU | $65,000-$95,000 |
| Above-garage ADU (if applicable) | $110,000-$155,000 |
Can a Junior ADU share utilities with the main house?
Yes, California law allows JADUs to share electric, gas, and water meters with the primary residence, which saves $4,000-$8,000 in separate service connections. We design the sub-metering or cost-sharing agreement into your permit set. Call (909) 323-1107 for an exact quote on your layout.
Does Pomona require owner occupancy for a JADU?
Yes, Pomona enforces the state requirement that the property owner live in either the main home or the JADU. We file the owner-occupancy affidavit with your permit application and note the covenant on title. Call (909) 323-1107 to confirm your situation qualifies.
ADU Site Prep & Utilities in Pomona
ADU site prep and utilities in Pomona almost always means electrical panel upgrades and sewer laterals on 1920s-1950s housing stock. The 60-amp and 100-amp panels common in north Pomona and Lincoln Park cannot power a modern ADU, and original clay sewer lines crack under new bathroom loads. We handle the full ADU Site Prep & Utilities scope before construction starts, so no surprise utility holdups delay your certificate of occupancy.
Electrical Panel Upgrade
Signs you need it
Your main panel is 100 amps or less, has no open breaker spaces, or shows scorch marks and buzzing.
What it costs in Pomona
Electrical panel upgrade in Pomona typically runs $4,500-$8,500 for 200-amp service including permit and SCE coordination.
How we do it
We pull the permit with Pomona Building & Safety, coordinate Southern California Edison’s service disconnect, install the new panel with ADU subfeed, and pass inspection before framing starts.
Plumbing Lateral
Signs you need it
Your home has original clay or cast-iron sewer line, you’ve had backups or slow drains, or the ADU adds a second bathroom to a single-bathroom house.
What it costs in Pomona
Plumbing lateral replacement in Pomona typically runs $8,000-$18,000 depending on length, depth, and street-to-house access.
How we do it
We camera the existing line, locate breaks or bellies, trench or trenchless to city main, and pressure-test before connecting the ADU fixtures.
What ADU Site Prep & Utilities Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Electrical panel upgrade | $4,500-$8,500 |
| Plumbing lateral replacement | $8,000-$18,000 |
| Foundation and grading (new detached) | $12,000-$28,000 |
Will SCE let me add an ADU meter later if I share now?
Yes, but trenching and conduit for a future separate meter costs roughly $2,000-$4,000 extra upfront, versus $8,000-$15,000 to retrofit. We note this option in your permit set so the infrastructure is ready. Call (909) 323-1107 to discuss your rental timeline.
How long does utility work add to my ADU timeline?
Panel upgrades and sewer laterals add 3-6 weeks in Pomona, mostly waiting for SCE scheduling and city inspection slots. We sequence this work before framing so it never sits on the critical path. Call (909) 323-1107 for a timeline tied to your specific address.
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. Our crews are fluent in these systems’ connection details and warranty requirements, and we stock common James Hardie trim and Tuff Shed hardware locally for fast turnaround on repairs or modifications. See our brands for full specifications.
Pricing for ADU in Pomona, CA
| Service | Typical range in Pomona |
|---|---|
| Interior JADU | $65,000-$95,000 |
| Room-to-ADU conversion | $85,000-$125,000 |
| Above-garage ADU | $110,000-$155,000 |
| Electrical panel upgrade | $4,500-$8,500 |
| Plumbing lateral replacement | $8,000-$18,000 |
| Foundation and grading (new detached) | $12,000-$28,000 |
| Gas line extension | $3,500-$7,500 |
| Landscaping and hardscape (post-build) | $5,000-$15,000 |
Prices push higher in Pomona when we encounter unpermitted casitas requiring survey and variance, hillside lots needing engineered retaining walls, or original knob-and-tube wiring still active in 1920s homes. Under Haven Standard Clause 1, your written price is locked at signing; no change orders for conditions we could not reasonably discover during our initial site visit.
Neighborhoods We Serve in Pomona
Our crews work across Pomona’s full footprint, from the historic districts to the Cal Poly perimeter. Dispatch and scheduling are coordinated from our Los Angeles office; crews serve Pomona locally with same-week site visits for feasibility assessments.
- Lincoln Park
- North Pomona (Craftsman district)
- Mayfair
- Downtown Pomona
- Westmont
Service Area - Cities Near Pomona
We design, permit, and build ADUs throughout the eastern San Gabriel Valley and western Inland Empire. Homeowners in Diamond Bar, CA and Chino Hills, CA face newer housing stock and stricter HOA environments, while Montclair, CA and Ontario, CA share Pomona’s inland heat and large-lot legacy but with different permit counter practices. We adjust our permit sets and construction sequences for each city’s specific requirements.
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 Development Services typically reviews complete ADU permit sets in 6-10 weeks, longer if your property has an unpermitted structure requiring survey or variance. We submit only after our pre-submittal meeting confirms your package is complete, which avoids the 4-6 week rejection-revision cycle common with incomplete applications.
Yes, but the Historic Preservation Commission reviews exterior materials, rooflines, and window proportions for compatibility. We produce renderings and material boards for HPC submittal as part of our standard permit set, not as an extra fee.
Often yes, but Pomona’s permit technicians will flag setback encroachment, especially on 4-foot side setbacks enacted after the structure was built. We survey first, then design either a variance application or a modified footprint that brings the unit into compliance without rebuilding.
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
"Handled the whole planning process. We went to one hearing and that was it."
- Rowena C."The rental income has covered the payment since the second month. They were realistic about the numbers rather than optimistic."
- Odette N."They walked us through setbacks and utility capacity before we paid anything, and told us one of our two options was not going to get approved."
- Mireille T.