Home Additions & ADU in Pomona - One Fixed Price, Permits Handled

Trusted Home Additions & ADU for Pomona Homeowners

Pomona Home Additions & ADU construction typically runs $45,000-$130,000 for room additions and $90,000-$220,000 for detached accessory dwelling units, with most projects quoted in writing before any permit is pulled. Rowan Construction Group has delivered 4,000-plus projects since 2007, every one with a flat written price and documented photo record, and we serve Pomona homeowners from the historic Lincoln Park district to the newer builds north of the 10 Freeway. Call (626) 606-1081 to schedule your free estimate.

Call (626) 606-1081

Pomona’s housing stock tells a story of pressure. Homes bought between 2015 and 2025 carry mortgages that don’t move, but families do - a new child, an aging parent, a grown kid back from college. Moving to Claremont or Diamond Bar Home Additions & ADU territory means another six-figure down payment and a higher rate. Adding square footage where you already live, with the lot you already own, is the math that now works for homeowners from Ganesha Hills to the Village at Indian Hill. We’ve built room additions over crawl spaces with active termite damage, converted 1950s Pomona garages into permitted junior ADUs, and navigated the city’s hillside grading requirements for second-story additions near Phillips Ranch. Every project started with a written price, a written scope, and a signed change-order discipline that kept final invoices within a few percent of the original number.

What Our Home Additions & ADU Service Includes

ADU Design & Permitting

An accessory dwelling unit needs a site plan, floor plan, and Title 24 energy calculations before Pomona Building & Safety will issue a permit. We produce construction documents in-house, coordinate with the city’s planning counter at 505 S. Garey Avenue, and revise for comments without billing hourly for every redline. Most Pomona ADU permits clear in 8-14 weeks depending on hillside overlays or historic district boundaries.

Garage Conversion ADU

Converting an existing garage skips foundation and roof work, which is why garage conversion ADUs in Pomona run $30,000-$80,000 rather than the $90,000-plus of new construction. We assess slab condition, ceiling height (Pomona requires 7’6″ minimum), and whether the garage shares a wall with the main house, which triggers fire-separation requirements. In the Mayfair area, we’ve converted detached garages with rotted sill plates; the photo record showed the owner exactly what we found and what we replaced.

New Detached ADU

A standalone unit on its own foundation gives maximum rental income and privacy, and Pomona allows detached ADUs up to 1,200 square feet on most single-family lots. We handle grading, utility trenching from the main house, and separate meter coordination with Southern California Edison. In the hills above Ganesha Park, we’ve built on slopes requiring retaining walls and engineered fill; the written quote included geotechnical referral, not a surprise later.

Junior ADU & Interior Conversion

A junior ADU, or JADU, lives inside the existing house footprint - a converted bedroom or attached garage with its own entrance and efficiency kitchen. Pomona allows JADUs up to 500 square feet and does not require additional parking if the unit is within the main structure. We verify ceiling heights, egress window requirements, and whether the existing electrical panel can handle a separate kitchen circuit. These projects finish faster than detached units, often 3-5 months from permit to final.

ADU Site Prep & Utilities

Before walls go up, we cut trenches for sewer and water laterals, run electrical conduit, and grade for drainage compliance with Pomona’s stormwater requirements. Clay-heavy soils in the western valley areas hold water; we specify perimeter drains and vapor barriers the quote includes, not discovers. Utility connection fees vary by distance from the main house; we measure and specify in the written scope.

Room Additions

A single-room addition - master bedroom, home office, expanded family room - attaches to the existing structure with matched rooflines and foundation ties. We open walls to inspect existing framing, sister rotten or inadequate studs, and specify whether the HVAC system can handle additional load or needs a mini-split. In Pomona’s 1940s-1960s stock, we regularly find unpermitted prior work that must be brought current; the photo record documents everything before we cover it.

Second Story Additions

Building upward preserves yard space and avoids setback issues, but requires structural verification that the existing foundation and first-floor walls can carry the load. We bring in a structural engineer for calculations, specified in the quote, and coordinate with Pomona’s building official for mid-project inspections. Ceiling heights, stair locations, and fire-rated assemblies between units all get drawn before we order lumber.

Sunrooms & Enclosed Patios

Enclosing an existing patio or building a new sunroom adds conditioned space without full ADU complexity. We specify insulated glass, conditioned slab or raised floor, and whether the space connects to central HVAC or needs dedicated heating and cooling. Pomona’s summer heat and winter Santa Anas mean glazing specification matters; we quote Low-E, argon-filled units with U-factors and SHGC ratings documented, not “energy-efficient windows.”

Brands We Service for Home Additions & ADU

We source and install across fifty-plus vetted brands, and we’ve worked with several prefabricated and modular ADU manufacturers that shorten on-site construction time. Mighty Buildings produces 3D-printed polymer composite units that ship in panels; we’ve coordinated foundation prep and crane sets for their 350-square-foot studio models in the Pomona area, managing utility tie-ins after the shell is placed. Boxabl delivers fold-out Casita units that unfold on a prepared slab in hours; we handle site grading, utility stub-outs, and final connection to city sewer and power. For homeowners wanting custom stick-built quality with factory precision, Plant Prefab manufactures wall and floor panels to our specifications, shipped flat and assembled on site by our crews.

Whether you have a Mighty Buildings, Boxabl, or Plant Prefab unit on order, or you’re starting from scratch with conventional framing, we can coordinate the site work, foundation, and utility connections. We also work with Tuff Shed structures for detached studios and workshop conversions that don’t require full ADU compliance. Every brand relationship is documented in the quote - model numbers, delivery windows, and who handles what - so there’s no gap between factory warranty and our workmanship guarantee.

Before

After

Signs You Need Home Additions & ADU Right Now

• Your household has outgrown the bedrooms you have. A third child, an aging parent moving in, or adult children returning home creates immediate need. Sleeping in converted dining rooms or shared offices is a temporary fix that becomes permanent stress; a room addition or JADU gives everyone defined space and preserves the home’s resale logic.
• Your garage has become unbuildable storage while your car sits outside. Pomona’s summer sun and occasional hail punish paint and interiors. Converting that garage to a permitted ADU generates rental income - $1,800-$2,400 monthly for a studio in the Pomona market - while you park under a carport we can specify separately.
• The city has flagged unpermitted work during a sale or refinance. We’ve opened walls to find unpermitted additions from prior owners, especially in Pomona’s older neighborhoods near downtown. Bringing work to code now, with documented photo records, protects your equity and prevents a buyer’s lender from killing the deal later.
• Your electrical panel is full and your HVAC runs constantly. These are symptoms of a house operating beyond its design load. A proper addition includes load calculations, panel upgrades, and right-sized mechanical systems; ignoring the infrastructure while adding space creates failures that cost more than the original project.
• You’re paying $3,000-plus monthly for assisted living you could provide at home. A JADU with accessible bathroom and kitchenette lets aging parents live independently on your property. The construction cost pays back against facility fees in 18-36 months, and the space converts to rental income later.

Our Home Additions & ADU Process - Step by Step

1. 1
   Site visit and written estimate. We walk your property, measure existing structures, and photograph conditions. Within 48 hours you receive a flat written price with line-item scope, material specifications by brand and model, and a project calendar. Under Clause 1 of The Haven Standard, this price is fixed before any work starts; no “allowances” that balloon later.
2. 2
   Design and permit submission. For ADUs and additions requiring plans, we produce or coordinate construction documents, submit to Pomona Building & Safety, and track comments. We revise for city feedback without change orders for standard plan corrections; only client-requested changes trigger new pricing, and only after you sign.
3. 3
   Site preparation and utility rough-in. We protect existing landscaping, trench for utilities, pour foundations or slabs, and install underground plumbing and electrical. The photo record documents soil conditions, drainage placement, and pipe depths; you receive the folder before framing begins.
4. 4
   Framing, systems, and inspection. Walls go up, roofs close in, and we rough in electrical, plumbing, and HVAC. Pomona requires inspection at foundation, framing, insulation, and final; we schedule and pass each before covering work. No drywall over uninspected framing, ever.
5. 5
   Finish, final inspection, and documentation. Flooring, fixtures, paint, and hardware complete the space. After final inspection and certificate of occupancy, you receive the photo record, signed warranty, and 365-Day Done Right Promise documentation. If anything is not done right, we make it right - backed by a terms page you can screenshot, not a handshake.

How Much Does Home Additions & ADU Cost in Pomona?

Home Additions & ADU Near Pomona - Our Service Area

We build across the Pomona Valley and surrounding communities, with typical project timelines that don’t change based on distance. Our crews work regularly in Montclair, where ADU permitting follows similar San Bernardino County procedures, and San Dimas, with its hillside grading requirements and larger lot sizes. We also serve Diamond Bar, Claremont, Walnut, Upland, Covina, Chino, Chino Hills, West Covina, and Ontario. Whether you’re in Pomona’s historic core or the newer developments near the 71 Freeway, the process is the same: site visit, written price, permit, build, document. Call (626) 606-1081 to schedule your free estimate.

Frequently Asked Questions - Home Additions & ADU in Pomona

Schedule Your Home Additions & ADU Service in Pomona Today

Call (626) 606-1081 to schedule your free estimate. You’ll receive a flat written price with line-item scope, specified brands, and a project calendar before any work starts - that’s Clause 1 of The Haven Standard, and it’s how we’ve kept 4,000-plus projects within a few percent of the agreed number since 2007. A live person answers calls 24/7, and every visit includes a documented photo record as standard. No obligation, no “call for a quote” - just the number in writing, the way careful contractors build.

Written by Grant Rowan, Owner at Rowan Construction Group, serving Pomona since 2007.