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 Sienna Plantation
Home additions and ADUs in Sienna Plantation run $45,000 to $130,000 for a room addition, and $90,000 to $220,000 for a detached ADU, depending on square footage, foundation work, and the HOA and county approval sequence. Most projects here face a two-step front-end approval that doesn’t exist a few miles away: the Sienna Plantation Residential Association’s Architectural Review Committee signs off first, then Fort Bend County accepts the permit application. That’s not a hurdle to work around. It’s the process we know well, and we scope it before you ever sign a draw schedule. Call (877) 610-1318 and we’ll walk your lot with you.
Why Barrett & Sons Construction Is Sienna Plantation’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998, and he still answers his own phone. When you’re planning a home addition or ADU in Sienna Plantation, you want the person on the other end to know what the ARC packet actually contains, not someone reading a script in another state. That’s how we work. Tom’s sons run the crews. Every price change arrives as a written change order before a single nail moves, and every eligible job includes permits pulled and inspections signed. We also carry the 90-Day Done Right Promise on every contract. If something’s not right, one call brings Tom back.
Sienna Plantation homeowners have a specific set of questions before they commit to a five-figure addition: Does my lot need ARC pre-approval? Will the black clay under my slab move? Is my septic and well location going to kill the ADU layout? We answer those on the first visit, in plain English, with numbers attached. We’ve done enough work off Sienna Parkway and around the community’s 77545 zip to know where the problems hide before the first footing is dug.
Our Home Additions & ADU Services in Sienna Plantation
We’re the Home Additions & ADU team that handles the full scope of work on your lot, from architectural drawings through final inspection. Here are the services Sienna Plantation homeowners ask about most.
New Detached ADU
A detached ADU on a Sienna Plantation acreage lot is a real structure with its own foundation, utilities, and ARC review. It’s not a shed with drywall. We scope it accordingly. We handle the full build, and on this soil, that means pre-soaking footing trenches before we pour, setting the finished floor elevation above the county’s post-Harvey BFE, and keeping the structure clear of existing septic and well setbacks. A detached ADU here typically runs $90,000 to $220,000, and the single biggest swing factor is site prep, not the building itself.
ADU Site Prep & Utilities
Before framing starts, the ground has to cooperate. The Vertisol clay in Fort Bend County swells with the Gulf Coast’s heavy seasonal rains and shrinks hard during summer dry spells. That movement opens gaps under slab perimeters. So we pre-soak, we compact, and we grade. We also verify your well and septic positions against county setback rules before any layout is locked. Moving a septic field on an acreage lot can add $30,000 or more, and that’s a number you should know on day one, not after drawings are done.
Garage Conversion ADU
Converting an attached garage into a junior ADU changes the way your home reads on paper, and in Sienna Plantation it can trigger questions about flood elevation certificates. Fort Bend County’s post-Harvey FEMA maps changed finished-floor requirements across the Brazos River corridor. We check that first. A garage conversion here runs $30,000 to $80,000, and we walk the HOA’s ARC packet through with you so the draw schedule matches the committee’s approval milestones, not the other way around.
Junior ADU & Interior Conversion
A junior ADU inside the existing footprint of your home is the fastest path to a rentable or family unit, and it generally costs less than a detached build. But the set of approvals is not zero. We handle the ARC conversation, the county permit, and the written change orders so the price on paper matches the price at the end. If you’re working off allowances, those allowances are written on the front of the quote, not hidden in a folder somewhere.
Second Story Additions
Adding a second story in Sienna Plantation means your existing slab and first-floor framing have to carry a load they were never designed for. Most homes here are 2000s to 2010s-era production tract builds by Lennar, Perry Homes, or Taylor Morrison, brick-veneer and slab-on-grade. We pull the drawings, verify the structural path, and run the numbers before you’re emotionally attached to a floor plan. This is a $45,000 to $130,000 conversation, and the condition of your existing roof line and foundation tells us most of what we need to know.
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 Sienna Plantation
We don’t install mystery materials off a van. When a Sienna Plantation addition or ADU calls for waterproofing, we use Schluter systems in wet areas. If the job includes roofing, we carry GAF. Homeowners who’ve been burned before want names they can look up, and that’s exactly what we give you. Our Sienna Plantation customers get the same brand names we’d install on Tom’s own house, and if a material is backordered, you hear it from us before it costs you a day on site.
Common Home Additions & ADU Problems We See in Sienna Plantation Homes
- Skipping ARC pre-approval before pulling the county permit. Fort Bend County will not issue an addition or ADU permit without the HOA’s sign-off in Sienna Plantation, and any work started early gets red-tagged. We’ve walked onto lots where a previous contractor poured footings first and asked questions later. It’s a costly fix.
- Pouring footings without pre-soaking the Vertisol. Black clay shrinks during the first dry season and opens gaps under the addition’s perimeter. In Sienna Plantation, we routinely pre-soak footing trenches for days before pouring. Out-of-area crews skip this and leave callbacks behind.
- Under-scoping drainage on an open lot. A room addition or ADU changes the sheet flow across your property. Post-Harvey FEMA grading rules make drainage plans a real engineering exercise, not a sketch on a napkin. Spring downpours will find the low spot you created.
- Placing an ADU before verifying the well and septic. Fort Bend County requires setbacks from both. On acreage lots around Sienna Plantation, moving a septic field can add $30,000 or more before framing starts. We locate everything before we draw a line.
Pricing for Home Additions & ADU in Sienna Plantation, TX
Here are the real numbers for Sienna Plantation’s market. These are not national averages. They reflect what we see on lots in the 77545 zip, with the HOA layer and the soil conditions already priced in.
| Project | Typical Range in Sienna Plantation |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
What moves the number? Square footage, foundation depth, drainage scope, septic or well work, and the ARC and county approval timeline. We write every allowance on the quote, every change order in writing, and we never hand you a bill at the end that wasn’t agreed to before the work happened. Call (877) 610-1318 for a free estimate on your Home Additions & ADU project. No trip charge inside the county.
We Also Serve Cities Near Sienna Plantation
Our crews serve Sienna Plantation and the surrounding communities, including Fresno, Missouri City, Manvel, and Stafford. If you’re just outside the neighborhood line, call (877) 610-1318 and we’ll tell you honestly whether we can get to your lot on the schedule you need. No games.
Serving Sienna Plantation, TX - Our Local Coverage Area
We’re based in the Sienna Plantation 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 Sienna Plantation
Yes. In Sienna Plantation, any home addition or detached ADU must first clear the Sienna Plantation Residential Association’s Architectural Review Committee before Fort Bend County will even accept a permit application. This two-step layer does not exist for acreage builds just across the county line in unincorporated Rosharon or Iowa Colony. Start with the ARC packet. Call (877) 610-1318 and we’ll help you assemble it.
Fort Bend County’s Vertisol clay shrinks and swells far more aggressively than the sandier fill north of here, and summer dry spells routinely open gaps under slab perimeters in Sienna Plantation. Our crews pre-soak footing trenches for days before pouring new concrete. That step gets skipped by out-of-area contractors and the callbacks show up within a single season. Budget for the dirt work. It’s not optional.
Fort Bend County requires specific setbacks from both the septic system and the well, and those distances shape where your ADU can go. If the existing septic field sits in the way of the only logical building site, moving it can add $30,000 or more before framing starts. We locate both on day one so the quote reflects reality, not optimism.
It can. Fort Bend County’s post-Harvey FEMA maps tightened finished-floor-elevation requirements along the Brazos River corridor, and a garage conversion changes the occupancy classification of that square footage. We check your current certificate against the county’s current requirements before drawings go in. Call (877) 610-1318 and we’ll walk the site.
Allowances are dollar amounts we set aside in the quote for materials you’ll select later, like flooring or fixtures. They’re bigger in Sienna Plantation because the ARC process and the soil conditions add coordination time and material choices that a flat-lot Missouri City build doesn’t face. Every allowance goes on the quote in writing. An allowance that isn’t on paper is a surprise waiting for a date.
Schedule Your Home Additions & ADU Estimate in Sienna Plantation
Tom Barrett’s name, address, and license number are published and verifiable. Look them up before you sign anything with anyone. Then call (877) 610-1318 for a free estimate on your room addition, detached ADU, garage conversion, or second story. A live person answers, 24 hours a day. We’ll schedule a time to walk your lot, talk through the ARC and county sequence, and put the whole scope in writing. We also offer a free second opinion on any written estimate and a permanent 10% Senior & Veteran discount. If you’re in Sienna Plantation, you’ll see us at the hardware store on Saturday. That’s the point.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Sienna Plantation and Fort Bend County.