ADU in Pomona, CA
Junior ADU & Interior Conversion in Pomona typically runs $80,000-$150,000 all-in for a room-to-ADU or interior JADU, while full ADU Site Prep & Utilities adds $25,000-$75,000 depending on whether your 1940s-1970s home needs a panel upgrade, new plumbing lateral, or both. We’re Ellery ADU Studio, and we handle the drawings, permit set, and construction under one contract at one written price - no designer-versus-builder blame gap. Call (840) 212-3065 to schedule your free estimate.
Pomona’s post-WWII housing stock - bungalows and ranch homes on 7,000-10,000+ sq ft lots - makes it one of the strongest garage-conversion and junior ADU markets in the eastern San Gabriel Valley. Many homeowners bought at lower price points than neighbors in Claremont or Pasadena, so the ROI on a $150K-$200K ADU pencils out faster here as a genuine wealth-building move rather than a luxury add-on. That same older infrastructure means nearly every project hits surprises: galvanized supply lines, 60-100A panels, and uninsulated garage slabs that must be upgraded to current Title 24 and habitability standards before the certificate of occupancy is issued.
Why Pomona Homes Are Different
Pomona sits deep in the Inland Valley heat pocket, where summer temperatures regularly push past 100°F - far beyond what coastal LA ADU specifications assume. A properly sized mini-split and well-insulated thermal envelope aren’t upgrades here; they’re requirements. Winter nights drop into the low-to-mid 30s, so the same unit must handle real heating loads, and single-zone mini-splits with adequate BTU capacity are our standard specification.
The city’s housing department also deals with a high density of unpermitted existing structures - backyard sheds, informal garage conversions, multigenerational additions built without permits over decades. Pomona typically requires owners to either fully legalize or demolish any unpermitted structure on the parcel before an ADU permit is approved. Homeowners who thought they were starting with a clean slate often face weeks of inspection and remediation before ADU construction can begin.
Electrical infrastructure is another local factor. The 60-100A panels common in Pomona’s 1940s-1970s neighborhoods cannot handle the additional load of a modern ADU with electric cooking, laundry, and HVAC. Virtually every garage conversion and many interior JADUs require a panel upgrade and often a new meter, adding cost that buyers frequently underestimate in early budgeting.
Our Main Pomona Services
Most Pomona homeowners start with one of these three core services, each with its own dedicated page and pricing detail.
ADU Design & Permitting in Pomona
Our permit set is the core product, not an afterthought. For Pomona’s older housing stock, we begin with a site survey that flags unpermitted structures, setback compliance, and utility capacity before a single drawing is drafted. The full permit package includes Title 24 energy calculations, structural calcs for existing foundation evaluation, and coordination with Pomona’s building department on any required remediation of prior unpermitted work. ADU Design & Permitting in Pomona covers the complete process from feasibility study through issued permit.
Garage Conversion ADU in Pomona
Pomona’s abundance of detached two-car garages on generous lots, combined with intense rental demand from Cal Poly Pomona students and staff, makes this one of our highest-ROI project types. Every conversion here requires slab evaluation, thermal envelope upgrade to Inland Valley specs, and almost always a panel upgrade. We coordinate the full build under our single contract with one written price. Garage Conversion ADU in Pomona details the complete scope.
New Detached ADU in Pomona
For homeowners with adequate rear yard space, a new detached unit avoids the constraints of existing structure remediation entirely. We design to Pomona’s setback and height limits, specify prefab systems from brands like Abodu or Cover when appropriate, and handle foundation, utilities, and final connection under the same contract. New Detached ADU in Pomona covers feasibility, design, and build 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 lets homeowners create a self-contained rental unit within the existing footprint - a room-to-ADU conversion, basement ADU, or attached addition - without building new exterior walls. For Pomona’s 1940s-1970s stock, this often means working around original galvanized plumbing, undersized panels, and no existing HVAC rough-in, all while meeting California’s JADU size limits (500 sq ft max) and separate entrance requirements. We handle the full design-build process including the permit set, and you can read more about our approach at Junior ADU & Interior Conversion.
Room-to-ADU Conversion
Signs you need it
You have an underused bedroom, den, or former rental room with exterior wall access and want legal rental income without new construction.
What it costs in Pomona
Room-to-ADU conversions in Pomona typically run $80,000-$120,000 all-in, including the panel upgrade and mini-split that most 1940s-1970s homes require.
How we do it
We verify ceiling height, add a separate exterior entrance, run new electrical and plumbing from the upgraded panel, install a dedicated mini-split, and submit the full permit set with Title 24 calcs.
Interior JADU
Signs you need it
You want the fastest path to legal rental income within your existing home and can dedicate up to 500 sq ft with a separate entrance.
What it costs in Pomona
Interior JADUs in Pomona typically range $60,000-$100,000, with the lower end applying when the existing panel already has capacity and no plumbing lateral extension is needed.
How we do it
We design the efficient kitchenette and bath layout, add the separate entrance, upgrade utilities as needed, and prepare the JADU-specific permit set with owner-occupancy affidavit.
What Junior ADU & Interior Conversion Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Room-to-ADU conversion (all-in) | $80,000-$120,000 |
| Interior JADU (all-in) | $60,000-$100,000 |
| Panel upgrade (when required) | $4,000-$8,000 |
Does a JADU require a separate kitchen and bathroom?
Yes. A legal JADU needs a kitchenette with cooking facilities, a separate bathroom, and its own entrance. We design these into compact, code-compliant layouts that maximize usable space within the 500 sq ft limit.
Can I convert a basement to an ADU in Pomona?
Yes, if ceiling height reaches 7’6″ minimum and emergency egress windows can be added. Pomona’s older homes often have partial basements with limited headroom, so we assess this in our initial feasibility visit. Call (840) 212-3065 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 be complete before framing begins: foundation and grading for new detached units, electrical panel upgrades for virtually every conversion, and plumbing laterals where original galvanized lines won’t carry additional load. Pomona’s triple-digit summers and sub-40 winter nights mean utility sizing isn’t guesswork - we specify for real thermal and electrical loads, not coastal assumptions. Learn more about our scope at ADU Site Prep & Utilities.
Electrical Panel Upgrade
Signs you need it
Your existing panel is rated 60-100A, has no open breaker spaces, or shows corrosion from Pomona’s temperature swings.
What it costs in Pomona
Panel upgrades in Pomona typically run $4,000-$8,000, including SCE coordination and new meter socket when required.
How we do it
We size the new 200A panel for ADU plus future load, coordinate Southern California Edison for service disconnect, and rough the new subpanel feed before inspection.
Plumbing Lateral
Signs you need it
Your home has original galvanized supply lines, low water pressure, or the city requires a separate water meter for the ADU.
What it costs in Pomona
Plumbing lateral replacement or extension in Pomona typically ranges $3,500-$7,500 depending on trench length and pavement restoration.
How we do it
We expose the existing lateral, specify copper or PEX replacement to the ADU stub, pressure-test before backfill, and coordinate with Pomona’s water department for meter separation if required.
What ADU Site Prep & Utilities Costs in Pomona
| Item | Typical range in Pomona |
|---|---|
| Electrical panel upgrade | $4,000-$8,000 |
| Plumbing lateral replacement/extension | $3,500-$7,500 |
| Foundation and grading (new detached) | $15,000-$35,000 |
Does every Pomona ADU need a panel upgrade?
Nearly every garage conversion and most JADUs do. Pomona’s 1940s-1970s housing stock was built for 60-100A service, inadequate for modern electric cooking, laundry, and HVAC loads. We verify capacity during feasibility and include the upgrade in your written price if needed. Call (840) 212-3065 for an exact quote - estimates are free.
Will Pomona let me share utilities with the main house?
JADUs may share utilities with owner-occupied main residences under state law, but detached ADUs typically require separate meters. Pomona’s building department enforces this strictly, and we coordinate the utility separation as part of our single-contract scope.
Brands We Service in Pomona
We specify and coordinate prefab and modular systems from Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie - all within the same single contract. Our Los Angeles office stocks common James Hardie siding and trim components for faster turnaround on custom builds, and we maintain direct coordination channels with Abodu and Cover for Pomona projects requiring accelerated delivery.
Pricing for ADU in Pomona, CA
| Service | Typical range in Pomona |
|---|---|
| Room-to-ADU conversion | $80,000-$120,000 |
| Interior JADU | $60,000-$100,000 |
| Above-garage ADU | $100,000-$160,000 |
| Basement ADU | $70,000-$130,000 |
| Attached addition ADU | $120,000-$180,000 |
| Electrical panel upgrade | $4,000-$8,000 |
| Plumbing lateral work | $3,500-$7,500 |
| Foundation and grading (new detached) | $15,000-$35,000 |
| Gas line extension | $2,000-$5,000 |
| Landscaping and hardscape restoration | $5,000-$15,000 |
Prices push higher in Pomona when unpermitted existing structures require remediation before permitting, when soil conditions demand deeper foundations, or when Southern California Edison requires service-line upgrades beyond the panel itself. Under Haven Standard Clause 1, every project receives a written price before any work begins - no call-for-pricing, no door-side upsells.
Neighborhoods We Serve in Pomona
We work across Pomona’s full residential footprint, from the historic Lincoln Park district to the postwar tracts near Cal Poly Pomona. Dispatch and scheduling are coordinated from our Los Angeles office; crews serve Pomona locally with same-week availability for estimates.
- Lincoln Park
- Mayfair
- Westmont
- Philadelphia Square
- Downtown Pomona
Service Area - Cities Near Pomona
Our crews work throughout the eastern San Gabriel Valley and western Inland Empire. We regularly schedule estimates in Diamond Bar, CA, Montclair, CA, Chino Hills, CA, and Ontario, CA, with the same single-contract design-build model and written pricing.
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 building department typically processes complete ADU permit applications in 8-14 weeks, though unpermitted existing structures on the parcel can add 4-8 weeks of remediation and re-inspection. We front-load the due diligence - survey, utility verification, and code analysis - to prevent mid-process surprises.
Pomona follows California’s statewide ADU standards for setbacks, height, and parking, but enforces stricter scrutiny of unpermitted existing structures and utility separation. We verify all parcel-specific conditions during our feasibility study and reflect any city-specific requirements in the permit set.
We are a design-build studio, not a standalone designer. Drawings, permit set, and construction are a single contract at a single written price. This eliminates the designer-versus-builder blame gap that derails most ADU projects, and it’s backed by our 365-Day Done Right Promise.
Call (840) 212-3065 to schedule your free estimate. A live person answers 24/7, and we offer a Free Second Opinion on any written estimate already in hand.
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."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.