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

Fast, Reliable Home Additions & ADU Across Union City

If you’re weighing a room addition or an ADU on a property in Union City, you’re probably already aware that this town’s flatland soils don’t let you simply pour a slab and start framing. Most of the homes between Alvarado Boulevard and Mission Boulevard sit on former bay marsh and alluvial fill, and Union City’s building department routinely asks for a geotechnical soils report before it will even look at your foundation drawings. That’s the reality here, and it’s a big reason why homeowners keep calling Union City locals like us. A full home addition in Union City typically lands between $45,000 and $130,000, while an ADU runs $90,000 to $220,000 depending on whether you’re converting a garage or building new. Call (877) 610-1318 and we’ll talk through what your specific lot needs.

Call (877) 610-1318

Why Barrett & Sons Construction Is Union City’s Preferred Home Additions & ADU Company

Tom Barrett started this company in 1998, and he still answers his own phone. When a Union City homeowner asks about a second story addition near James Logan High School or a detached ADU off Decoto Road, Tom’s the one walking the site, not a salesman from three time zones away. His sons run the crews, which means the person shaking your hand is the person whose name is on the truck.

We’ve pulled permits and passed inspections on jobs across the 94587 zip code for over two decades. The permit inspector works for you, not for us, and that’s exactly how Tom likes it. We carry a 90-Day Done Right Promise on every contract. If something’s not right, one call brings Tom back. Not a customer service department. Tom.

Every scope, every allowance, every price change lands in your hands as a written change order before a single nail moves. That’s not a soft promise. It’s how we’ve done business since day one, because the allowance that isn’t on paper is a surprise waiting for a date.

Our Home Additions & ADU Services in Union City

We’re an owner-operated shop, not a franchise dispatching strangers. Our Home Additions & ADU work in Union City covers everything from bump-outs to full detached units. Here’s what most folks call us about:

ADU Design & Permitting

Union City sits in a designated Seismic Hazard Zone for liquefaction across much of its flatland, which means your ADU plans will likely need a licensed geotechnical engineer’s soils report before foundation permits get issued. That step alone can add four to six weeks before construction starts. We set expectations around that upfront, on the first call, so you’re not surprised later. We’ll handle drawings, engineering, and all permit paperwork through Union City’s building department.

Garage Conversion ADU

In Union City, a garage conversion typically runs between $30,000 and $80,000, and it’s the most common ADU path for homeowners in the tract neighborhoods built in the 1960s and 70s. Those older slabs often have moisture issues from the shallow groundwater table near the bay, which means we regularly see concrete deterioration that has to be addressed before any framing goes up. We check for that, because skipping it means cracked walls inside your new unit two years from now.

New Detached ADU

For lots wide enough to fit a detached unit behind the main house, you’re looking at $90,000 to $220,000 in Union City. The price swings on foundation engineering, utility trenching, and whether your parcel sits closer to the old Alvarado salt pond margins or on slightly higher ground toward the hills. We’ll give you a written line-item quote with real numbers, not a vague estimate you can’t hold us to. Keep in mind we also handle Kitchen Remodeling in Union City if you’re planning to update the main house while we’re on site.

Junior ADU & Interior Conversion

If you’ve got a bonus room, an oversized laundry, or a den with its own entrance, converting it into a Junior ADU is often the fastest and most affordable route. Union City’s single-story stucco-over-wood-frame homes from the 1960s and 70s frequently have layouts that lend themselves to this kind of work without touching the exterior walls. We also do Bathroom Remodeling in Union City as part of many JADU projects, since adding a kitchenette and full bath is usually the core of the conversion.

Trusted Brands We Service in Union City

You won’t see mystery materials off the back of a van on our jobs. For hardscape and outdoor work tied to ADU site prep, we install Belgard and Techo-Bloc products, and we keep local stock accessible for Union City customers so we’re not waiting on a freight truck while your permits sit approved. GAF and CertainTeed go on every roof we tie into for Union City Roofing projects, and windows are Andersen or Marvin. These are brands you can look up. Tom’s name is on the job, so the materials carry the same weight.

Common Home Additions & ADU Problems We See in Union City Homes

• Liquefaction-zone foundation requirements. Union City’s building department commonly requires a geotechnical soils report before foundation permits are issued, especially near the former Alvarado salt pond margins. Out-of-area contractors often miss this until week three, and suddenly your timeline shifts by a month.
• Deteriorating 1960s-era slabs. The shallow groundwater table in Union City’s flatlands accelerates concrete breakdown in slabs poured during the incorporation-era building boom. We’ve had to saw-cut and repour sections of slab on garage conversions more times than we can count.
• Wind-driven moisture in exterior walls. Diablo winds off the bay push water into wall assemblies harder here than in Fremont’s hillside tracts. Flashing and envelope details on new additions have to be done right, or you’ll find rot inside a wall five years after the final inspection.
• Soft-story and cripple-wall conditions in older Decoto and Alvarado district homes. Pre-WWII wood-frame houses in those pockets frequently need foundation assessment before an addition goes up, because the original framing wasn’t built for a second story.

Pricing for Home Additions & ADU in Union City, CA

We Also Serve Cities Near Union City

Our crews work across Union City and the surrounding east bay, including Newark, Fremont, Fairview, and Hayward. If you’re just over the line and wondering whether we cover your street, call (877) 610-1318. Chances are we were on a job two blocks from you last week.

FAQs - Home Additions & ADU in Union City