Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across Alvin
Home additions in Alvin typically run $45,000-$130,000 for a full room addition, while a detached ADU ranges $90,000-$220,000 depending on size, foundation work, and floodplain requirements. Those numbers account for something most out-of-town contractors miss: Brazoria County’s post-Harvey floodplain rules apply to nearly every structural project here, sometimes even interior work that touches load-bearing walls. We’ve built additions and ADUs across Alvin long enough to know where the county will push back before we submit the first drawing. If you’re weighing a garage conversion, a second story, or a backyard cottage, call (877) 610-1318 and we’ll walk you through what’s realistic for your lot and your budget.
Why Barrett & Sons Construction Is Alvin’s Preferred Home Additions & ADU Company
Tom Barrett started Barrett & Sons in 1998, and the name on the truck still answers the phone. Our Home Additions & ADU team works the same way in Alvin that we do everywhere else: permits pulled on every eligible job, written change orders before any scope moves, and a 90-Day Done Right Promise on the contract. The difference in Alvin is that we already know the county’s floodplain administrator will ask for finished floor elevation documentation on most structural work, so we file it up front instead of waiting for the plan review to stall.
Alvin homeowners tell us the same story again and again: a national outfit quoted one price, then handed over a different invoice after the slab was poured. That doesn’t happen with us because every allowance and every change arrives in writing before work proceeds. Our crew members are background-checked and they carry the Barrett & Sons name, not a subcontractor’s logo. When you call, a live person answers 24/7, not a voicemail box in another state.
Our Home Additions & ADU Services in Alvin
ADU Design & Permitting
Designing an ADU in Alvin isn’t just about floor plans. The Brazoria County floodplain management overlay means your finished floor elevation, flood vents, and foundation type all get scrutinized before the first inspection. We handle the drawings, the county submittal, and the elevation certificates so your accessory dwelling unit clears review without weeks of back-and-forth. Most Alvin ADU permit packages we do come with a written scope and a line-item budget before anything goes to the county.
Garage Conversion ADU
A garage conversion in Alvin typically runs $30,000-$80,000, and the range depends heavily on whether your existing slab sits below Base Flood Elevation. Many homes along Gordon Street and South Street were built before modern elevation codes, so converting that garage into a rentable unit often means raising the floor, adding flood vents, and sometimes reinforcing the original slab. We inspect the existing structure first, then tell you honestly whether a conversion makes sense or whether a new detached unit would cost you less over time.
New Detached ADU
New detached ADUs in Alvin run $90,000-$220,000 because you’re pouring a new foundation on Beaumont Clay soil that heaves with every wet-dry cycle. That soil alone justifies deeper footings and reinforced slabs, and the county will require flood-resistant materials below the Base Flood Elevation. We build detached units in the subdivisions along Highway 35 and the older lots near the original townsite, and we design each one to the specific elevation certificate for that parcel, not a generic plan from a catalog.
Junior ADU & Interior Conversion
A junior ADU is the fastest path to extra living space in Alvin: convert an existing bedroom, den, or oversized utility room into a semi-independent unit with its own entrance and kitchenette. These projects often fall under interior remodel rules, but if you touch structural walls, Brazoria County still wants to see how the work interacts with floodplain requirements. We’ve done enough of these in Alvin to know exactly what the plan reviewer will flag, so the permit doesn’t become a surprise.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Alvin
We carry premium materials you can actually look up. For ADU kitchens and wet bars, we install Schluter waterproofing systems and Grohe fixtures because they hold up in Alvin’s humidity and they’re warrantied by manufacturers who answer the phone. On addition roofs, we use GAF shingles with reinforced decking and ring-shank nailing patterns rated for the wind speeds Gulf storms still carry this far inland. If you’re converting a garage or building a detached unit, you’ll know every brand going in because it’s written on the scope, not described vaguely over the phone.
Common Home Additions & ADU Problems We See in Alvin Homes
- Slab heave on Beaumont Clay: Alvin’s expansive clay soil swells and shrinks with seasonal moisture, and older slabs move with it. Any addition that ties into an existing slab needs a soil assessment and, often, deeper footings than a plan drawn for Houston would call for.
- Below-BFE original construction: Many post-WWII bungalows and 1960s-70s ranch homes in Alvin sit below current FEMA Base Flood Elevation. When you add on or convert, the county may require raising finished floors, adding flood vents, or both, which changes the budget and the schedule.
- Wind-rated roof connections: Alvin sits far enough inland that people forget tropical systems still arrive at Category 1-2 strength. Additions with 2×4 rafters toe-nailed into the top plate fail earlier than homes with hurricane clips and ring-shank fastening.
- Floodplain plan review stalls: A contractor unfamiliar with Brazoria County will submit plans without the elevation certificate, get bounced, and lose two or three weeks. We file the floodplain documentation with the first submittal because we’ve learned that lesson for you.
Pricing for Home Additions & ADU in Alvin, TX
Here’s what we quote in Alvin, in writing, before we start: full room additions $45,000-$130,000, detached ADUs $90,000-$220,000, garage conversions $30,000-$80,000, and junior ADUs or interior conversions usually land in the $40,000-$85,000 range depending on plumbing and electrical scope. The Alvin-specific variables are foundation elevation, flood venting, and soil correction on Beaumont Clay, all of which show up as line items, never as a vague “site conditions” charge at the end. We offer free estimates, no trip charge inside the county, and every price change arrives as a written change order before work happens. Call (877) 610-1318 and we’ll give you real numbers for your lot, not a national average.
We Also Serve Cities Near Alvin
Our crews work throughout northern Brazoria County and the southern edge of Harris County, including Manvel, Friendswood, Pearland, and Webster. The floodplain requirements in Pearland differ from Alvin’s, and we adjust the plan set accordingly, but the same written scope and same 90-Day Done Right Promise follow us to every job. If you’re just outside Alvin, we’re already familiar with your local permit office too.
Serving Alvin, TX - Our Local Coverage Area
We’re based in the Alvin 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 Alvin
We schedule free estimates in Alvin within a few business days, and there’s no trip charge inside Brazoria County. Call (877) 610-1318 and a live person answers 24/7 to set a time that works for you.
Yes, every eligible job includes permits pulled and inspections signed. In Alvin, that includes the Brazoria County floodplain review, finished floor elevation documentation, and any elevation certificates your parcel requires before we break ground.
Many older Alvin homes built before modern FEMA mapping sit below Base Flood Elevation, and county rules often require flood-resistant materials, venting, or raised finished floors when you add on structurally. We assess your specific parcel and tell you what applies before you commit to a design.
Garage conversions in Alvin run $30,000-$80,000, while new detached ADUs run $90,000-$220,000. The gap comes from foundation work and floodplain compliance, which are heavier on new construction. We’ll give you a written comparison for your specific lot, not a generic range.
We offer a permanent 10% Senior & Veteran discount, plus $40 off any repair over $200 and a free second opinion on any written estimate you’ve received from another contractor. Bring us a competitor’s written scope and we’ll tell you where the surprises are hiding.
Every job includes our 90-Day Done Right Promise in writing. If something isn’t done right, Tom Barrett comes back to make it right, one call. We also pass through manufacturer warranties on the materials we install, like GAF roofing and Schluter waterproofing.
If you’re planning an addition or ADU in Alvin, call (877) 610-1318 today for a free estimate with no trip charge inside the county. We’ll walk your lot, review the floodplain requirements, and give you a written scope with real numbers, and then you decide if you want to move forward. No pressure, no vague allowances, no surprises at the end.
Written by Tom Barrett, Owner at Barrett & Sons Construction.