A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Union City, CA
Adding an ADU in Union City costs between $180,000 and $380,000 for a detached unit, while garage conversions run $95,000 to $160,000. What makes Union City different: the city waives all ADU impact fees and its ADU Express counter routinely issues permits in under 30 days. Homes here are mostly 1950s-1970s ranchers and split-levels on 5,000-7,000 sq ft lots, which means real backyard space but also clay-heavy soil and shallow sewer laterals that shape how we place and build. If you’re weighing your options, call (669) 266-4319 and we’ll walk you through what your lot can actually support.
Why Union City Homes Are Different
Union City’s housing stock comes from a specific window: post-war tract ranchers and split-levels built fast, on flat land, with one-story slab foundations. The lots are generous by Bay Area standards, but the soil is not. Flat, clay-heavy ground near the bay expands in wet winters and contracts in dry summers, which means foundation drainage and crawlspace ventilation have to be designed correctly from the start or you’ll be chasing moisture problems for years.
The climate works in your favor for detached ADUs. Mild summers with coastal fog and wet, cool winters mean insulation and vapor barriers matter more than air conditioning. We also pay close attention to sewer laterals in these older tracts – many are shallow, and adding a bathroom and kitchen to the backyard sometimes requires creative plumbing routing to tie into the main line without tearing up half the yard.
The planning picture is genuinely friendlier here than in Fremont or Hayward. Union City’s ADU ordinance waives all impact fees and allows ADUs up to 1,200 sq ft on any residential lot. The ADU Express counter has permits out in under 30 days on a regular basis. That combination – no fees, fast approvals – is rare in the Bay Area, and it changes the math on whether a project pencils out.
Our Main Union City Services
Most Union City homeowners come to us for one of three projects: a home addition, a garage conversion, or a detached ADU. Each has its own page with local pricing, permit notes, and what to expect on a Union City lot.
Home Addition Contractor in Union City
Additions on these 1950s-1970s ranchers usually mean extending the back or side of the house, which brings the slab foundation and clay soil into play immediately. We match roof lines and stucco so the new section doesn’t look bolted on, and we plan drainage around the addition footprint from day one. Whether it’s a new primary suite, a family room, or a second story over the garage, the work starts with a written price and a real plan. Learn more on our Home Addition Contractor in Union City page.
Garage Conversion Contractor in Union City
Union City garages from the 60s and 70s are often the fastest path to livable space – the structure is already there, and converting it usually avoids the foundation work a detached ADU requires. The tradeoffs are insulation, electrical capacity, and losing covered parking, which is tougher in neighborhoods with tight street parking. We handle the full conversion: slab leveling, walls, insulation, a new entry, and bringing the electric and plumbing up to code. Details are on our Garage Conversion Contractor in Union City page.
ADU Builders in Union City
Detached ADUs make the most sense on Union City’s larger lots, especially within walking distance of the BART station where rent demand from commuters is steady. We build stick-framed units and also work with prefab manufacturers where the lot and budget call for it. Backyard placement, setback compliance, and drainage are the three things that make or break these projects in Union City, and we handle all three before we ever break ground. See specifics and pricing on our ADU Builders in Union City page.
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.
Brands We Service in Union City
We install and finish ADUs from our brands including Tuff Shed, James Hardie, Abodu, and Cover. Most prefab units we work with are finished with James Hardie siding for moisture resistance in Union City’s damp winter air. Parts and replacement pieces for these systems are stocked locally, so a warranty follow-up doesn’t mean waiting on a shipment from the factory.
Pricing for ADU Company in Union City, CA
| Service | Typical range in Union City |
|---|---|
| Detached ADU (600 – 800 sq ft, stick-built) | $180,000 – $280,000 |
| Detached ADU (prefab) | $150,000 – $240,000 |
| Garage conversion to ADU (400 – 500 sq ft) | $95,000 – $160,000 |
| Home addition (300 – 500 sq ft) | $120,000 – $220,000 |
| JADU conversion (attached, under 500 sq ft) | $80,000 – $140,000 |
| Site prep, foundation, and utility connections | $25,000 – $60,000 |
| Soft costs (permits, plans, engineering) | $10,000 – $25,000 |
What pushes a Union City project toward the high end is usually soil work: bad drainage, clay expansion, or a shallow sewer lateral that needs to be rerouted. You’ll hear a hard number from us before any work starts, in writing, without price changes at the door. That’s The Kingswell Way.
Neighborhoods We Serve in Union City
We work across Union City, from the older rancher tracts south of Alvarado Boulevard to the neighborhoods east of Mission Boulevard and the pockets near the BART station where commuter rental demand is strongest.
- Decoto
- Alvarado
- Seven Hills
- The Skylark area near BART
- Mission Ranch
For most jobs, we can have a crew on site within a week of the signed contract, depending on permit timing at the ADU Express counter.
Service Area – Cities Near Union City
We also take on ADU, garage conversion, and addition projects in nearby Bay Area cities. If your property is in Fremont, CA, Palo Alto, CA, Milpitas, CA, or Los Altos, CA, we can help there too. Each city has its own permit quirks, and we handle them the same way: written price, real arrival window, and a written guarantee on the finished work.
Serving Union City, CA - Our Local Coverage Area
We’re based in the Union City 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 Company in Union City
Union City’s ADU Express counter typically issues permits in under 30 days, which is faster than most neighboring cities. Plan on that timeline for the building permit itself; plan review, engineering, and any corrections can add a few weeks. We handle the submittal and track it through approval so you don’t have to. Call (669) 266-4319 for a realistic timeline on your specific lot.
No. Union City’s ADU ordinance explicitly waives all impact fees for accessory dwelling units, which saves homeowners $10,000 to $35,000 compared to cities that still charge them. That’s one reason an ADU pencils out well here. The waiver applies to both attached and detached units up to 1,200 sq ft. We’ll confirm your project qualifies before we write the quote.
Once the permit is issued, we typically schedule work within one to two weeks, depending on crew availability and weather. Union City’s wet winters can delay foundation work, so we plan pours around the forecast. The Kingswell Guarantee includes a defined arrival window, so you’ll know exactly when the crew shows up. Call (669) 266-4319 to talk dates.
Ready to talk numbers? Call (669) 266-4319 for a free, written estimate on your Union City ADU, garage conversion, or home addition. 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 Union City Customers Say
"Converted our garage into a rental studio. The crew was respectful of the neighbors and kept the site clean. It's bringing in rent now and paid for itself faster than I expected."
- Grace Yoon"Built a backyard unit for my mother in law. They handled the permits, gave me a real timeline, and stuck to it within a few days. The written price is what we paid, which anyone who's done construction knows is rare."
- Dennis Fairchild"Added a suite for my dad. They walked us through every cost before a hammer swung and stuck to it. The written price is what we paid, no change orders."
- Ingrid Salazar
