Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Before
After
Before
After
Before
AfterFast, Reliable Home Additions & ADU Across Modesto
Home additions and ADU construction in Modesto typically run $45,000 to $130,000 for a room addition, and $90,000 to $220,000 for a new detached ADU, with garage conversions landing between $30,000 and $80,000. Those are the numbers we quote across the 95351, 95352, 95353, and 95354 zip codes, and they reflect what it actually costs to build here, where the valley clay under your slab has been moving for decades and the east-side tract homes carry 20 years of deferred maintenance. Barrett & Sons Construction has been building in the Central Valley since 1998, and Tom Barrett’s sons run the crews that serve Modesto, so the person who shakes your hand is the same person you’ll see at the lumberyard. Call (877) 610-1318 and we’ll come out, walk the property, and put a written scope in front of you before you spend a dime.
Why Barrett & Sons Construction Is Modesto’s Preferred Home Additions & ADU Company
We’re not a franchise that dispatches strangers to Modesto. Tom Barrett founded this company in 1998, and his sons run the crews that work the east side, the west side, and the older core neighborhoods around 95350 through 95354. When you call, a live person answers the phone, and when there’s a question about your job, you talk to the person who will actually build it.
Modesto homeowners hire us because we put everything in writing. The scope, the allowances, and every price change arrives as a written change order before a single nail moves. The permit inspector works for you, not for us, and that’s exactly how we like it. Every eligible job pulls permits and gets inspections signed. We have been doing it that way for over 29 years.
Our Home Additions & ADU team knows what happens to Modesto slabs when the tule fog lifts and the summer sun bakes the ground hard again. That’s not something you learn from a manual. It’s something you learn from digging footings in this soil for almost three decades. Look up Tom Barrett’s name, address, and license number before you sign anything. Then ask anyone on your street. We’d rather you check first.
Our Home Additions & ADU Services in Modesto
ADU Design & Permitting
A new ADU in Modesto means working with Stanislaus County and city planning rules that changed over the years, and the permit process still trips up homeowners who try to shortcut it. We handle the full design and permitting package for you, from first sketch to final inspection. Our Home Additions & ADU team in Modesto has pulled permits for every type of ADU this city allows, and we walk you through setbacks, lot coverage, and utility tie-ins before you’re committed to a plan.
Garage Conversion ADU
Garage conversions in Modesto run $30,000 to $80,000 depending on whether you’re converting an attached two-car garage or a detached structure, and how much plumbing and electrical work the existing building needs. Modesto’s east-side subdivisions, particularly around 95355 and 95356, have garages that were built fast during the early-2000s boom, and we often find slab hairline cracks and moisture intrusion that have to be addressed before the conversion can pass inspection. We also handle complete Kitchen Remodeling in Modesto when a garage conversion includes a kitchenette or a full kitchen.
New Detached ADU
A new detached ADU in Modesto is a $90,000 to $220,000 project, and that range depends on size, foundation work, site prep, and the level of finish you choose. The valley clay under most Modesto lots expands in wet winters and shrinks in summer, so we don’t pour a slab without assessing soil movement first. We build detached ADUs from the ground up, including foundation, framing, utilities, and all finish work, with change orders in writing every step of the way.
Junior ADU & Interior Conversion
A junior ADU, or JADU, is often the most cost-efficient way to add rental income or space for an aging parent without a full detached build. These interior conversions typically work within the footprint of the existing home, which keeps the price lower than a new structure. We also partner with homeowners on Bathroom Remodeling in Modesto when a JADU needs an added bath or a refreshed one, and we coordinate the whole job so the plumbing and electrical work happens in the right sequence.
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.
Trusted Brands We Service in Modesto
We stock and install materials you can look up, not mystery brands off a van. For ADU bathrooms and wet areas, we carry Schluter waterproofing systems and Grohe fixtures. For kitchens inside your ADU or addition, we install Sterling and Grohe plumbing products that hold up to years of rental use. We keep inventory for our Modesto jobs at our Central Valley facility, which means fewer delays when a fixture needs replacing mid-project.
Common Home Additions & ADU Problems We See in Modesto Homes
- Slab movement from valley clay. Modesto’s expansive adobe-clay soils heave and shrink between wet winters and drought summers, and east-side slabs poured in the 1990s and 2000s have often moved an inch or more since the final inspection. That movement shows up as diagonal stucco cracks at window corners and interior doors that no longer latch, and any addition or ADU tied into that slab needs a soils assessment before we design the connection.
- Deferred maintenance from the foreclosure era. Modesto was one of the hardest-hit cities in the country during the 2008-2010 foreclosure crisis, and thousands of east-side tract homes sat vacant or changed hands repeatedly. We routinely find substandard flip-era repairs, moisture intrusion, and code violations that have to be remediated before an addition or ADU can be built legally.
- Heat-cracked concrete and roof decking. Summer temperatures above 105°F are normal in Modesto, and years of that exposure do real damage to concrete flatwork and roof sheathing. We schedule pours and roofing before 10 a.m. to avoid accelerated curing failures, and we account for heat expansion when tying a new addition into an existing roofline.
- Tule fog delays and moisture buildup. Dense tule fog socks in Modesto from December through February, sometimes for days at a stretch, and it grounds exterior framing, grading, and roofing work in a way coastal contractors don’t plan around. We build that reality into our Modesto schedules so your project timeline reflects what actually happens here, not what works in Sacramento or the Bay Area.
Pricing for Home Additions & ADU in Modesto, CA
Here are the numbers we quote in Modesto, and they hold from the initial written estimate through final inspection unless you approve a written change order. A home addition in Modesto runs $45,000 to $130,000 depending on size, foundation, and finish level. A detached ADU runs $90,000 to $220,000. A garage conversion runs $30,000 to $80,000. A junior ADU or interior conversion typically comes in below a detached build, though the final number depends on plumbing and electrical scope.
What moves the price most in Modesto is the condition of the existing slab and the soil beneath it. East-side lots with documented movement need deeper footings or engineered solutions, and that’s an item we put in writing before you commit, not something we discover after demolition starts. Call (877) 610-1318 for a free estimate and we’ll give you a written line-item scope with real numbers.
We Also Serve Cities Near Modesto
Our Home Additions & ADU in Modesto team works the surrounding communities too, including Bret Harte, West Modesto, Ceres, and Riverbank. If you’re a few miles outside the city line, give us a call. There’s no trip charge inside the county, and we’ll tell you straight whether your job is something we can take on.
Serving Modesto, CA - Our Local Coverage Area
We’re based in the Modesto 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 - Home Additions & ADU in Modesto
We answer the phone live, 24/7, and we schedule free estimates in Modesto within days, not weeks. Crews are based in the Central Valley, so we’re not driving from Sacramento or the coast. Call (877) 610-1318 and we’ll get you on the schedule.
Yes. We work across the older core around 95350 through 95354, the east-side subdivisions around 95355 and 95356, and the surrounding areas out to Bret Harte, West Modesto, Ceres, and Riverbank. If your address is in Modesto or just outside the line, call us and we’ll confirm coverage.
For structural issues like a cracked addition wall, a failing header, or water intrusion into an existing garage conversion, we respond the same day or next day depending on severity. For new construction and planned additions, we schedule the work and build the tule fog and summer heat into our timeline. Call (877) 610-1318 and tell us what’s going on.
Modesto pricing runs comparable to Ceres and Riverbank, and slightly below Bay Area pricing. What drives cost here more than anything is the condition of the underlying soil and the existing structure. We quote real numbers in writing, and every change order comes before the work, so the price you’re quoted is the price you pay unless you approve a change in writing.
Yes. Every construction and remodeling job we do in Modesto is backed by our 90-Day Done Right Promise, written on the contract, not buried in fine print. If it’s not done right, Tom comes back and makes it right with one call. Call (877) 610-1318 to schedule your free estimate.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Modesto since 1998.