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Get your free estimateFast, Reliable Home Addition Contractor Across Round Rock
A home addition in Round Rock typically costs between $95 and $260 per square foot, with most projects landing between $120,000 and $340,000 depending on scope, finishes, and whether your lot sits on expansive clay or an older septic system. That’s a wide range because Round Rock’s housing stock varies dramatically, from 1990s tract homes in Brushy Creek to newer builds in Teravista and older Chisholm Valley properties with their own site constraints. We know the difference between what a builder warranty allows in a 2018 home versus what an 80s septic system will tolerate before the city signs off. If you’re planning a bedroom or sunroom addition, call us at (254) 615-3842 for a written price before any work starts.
Why Seedling ADU Austin Is Round Rock’s Preferred Home Addition Contractor Company

Round Rock homeowners call us because we show up with a plan that accounts for HOAs, clay soil, and the city’s permitting process before a single tool leaves the truck. Our Home Addition Contractor team has walked through enough Teravista architectural review meetings to know which roofline changes get approved and which get sent back. We also know that a stop-work order from an HOA committee costs more than any design change ever will.
Every project starts with a written price. Not an estimate range scrawled on a business card. A line-item price you can take to your lender or your kitchen table. That price includes the Cedarwell Care Promise: shoe covers and drop cloths inside your home, pet-safe products where there is a choice, and a photo of the clean-up before the crew leaves each day. Ben Ortega leads our Round Rock work, and he holds every job to the 365-Day Done Right Promise. If it isn’t done right, we make it right. In writing. Call (254) 615-3842 and a live person answers, 24/7.
Bedroom Addition Contractor in Round Rock
A bedroom addition in Round Rock gives a growing family room to breathe without moving out of the neighborhood, and it typically runs $55,000 to $95,000 for a standard 12×14 room with closet, drywall, paint, and electrical. The first question we ask is which side of Round Rock you live on, because the answer changes the job. In Teravista or Brushy Creek, HOA architectural review drives the schedule. In Chisholm Valley, the original septic system often drives whether the project moves at all. We check both before we quote, so your written price reflects what will actually happen on your lot.
Expanding Without Moving
A bedroom addition works when the rest of the house fits but one room doesn’t. We frame, insulate, drywall, finish, and tie into your existing HVAC. For older tract homes with builder-grade systems, we often add a high-efficiency mini-split rather than overloading a furnace sized for 1,800 square feet.
Foundation Work on Round Rock Clay
Round Rock’s expansive clay soil moves with the seasons, and a bedroom addition needs a slab engineered for that movement. City inspectors look hard at drainage and grade on every permit. Our plans include that drainage detail up front, not as a surprise revision.
Sunroom Addition in Round Rock

A sunroom addition in Round Rock adds light and livable square footage for $45,000 to $110,000, depending on whether you choose a three-season room or a fully conditioned four-season build with its own HVAC. Central Texas heat is the real test of a sunroom. Low-e glass, proper roof insulation, and a dedicated ductless unit matter more here than they would in a milder climate. We price sunroom additions with those specifics included, because a sunroom that hits 95 degrees in July isn’t a room, it’s a greenhouse.
Three-Season Rooms for Mild Months
October through April in Round Rock is glorious. A three-season sunroom with operable windows and ceiling fans captures that stretch without the cost of full HVAC integration. Most homeowners use these rooms for morning coffee, plants, or homework space.
Four-Season Rooms With Real Climate Control
If you want the room usable in August, we recommend a four-season build with insulated glass, a mini-split, and a roof tied into your home’s thermal envelope. The price difference is real, but so is the difference between a room you use 250 days a year and one you avoid for five months of Round Rock heat.
Trusted Brands We Service in Round Rock
We install and finish additions around the systems and materials Round Rock homeowners already trust. That includes prefab and panelized options from Cover and Dvele, which work well on lots where HOA rules favor faster exterior completion. We also work with Mighty Buildings components when a homeowner wants a shorter on-site timeline without sacrificing the brick-veneer match Teravista and Brushy Creek committees expect. Our team keeps local suppliers on speed dial for Round Rock jobs, so hardware, trim, and window orders move without days of downtime.
Common Home Addition Contractor Problems We See in Round Rock Homes
- HOA stop-work orders in Teravista and Brushy Creek. Architectural review committees in these master-planned communities require design approval before construction. Starting without that stamp leads to fines and halted work. We submit plans with the specific roofline, exterior finish, and setback details each HOA wants to see.
- Septic surprises in Chisholm Valley. Original 1980s septic systems on older lots often can’t handle a second dwelling or additional bedroom. The City of Round Rock requires an aerobic system upgrade before it will approve permits in many of these cases. We check system capacity before we draw plans, not after.
- Expansive clay and foundation cracks. Round Rock sits on soil that swells when wet and shrinks when dry. A poorly drained addition slab will crack and shift within a few seasons. Our plans include moisture barriers, proper grading, and drainage details that meet city inspection standards.
- Builder-grade HVAC that can’t keep up. Many 1990s and early 2000s tract homes were built with systems sized to the original footprint. Adding 300 square feet without addressing airflow leaves the new room hot in August and cold in February. We rebalance ductwork or add a ductless unit as needed.
Pricing for Home Addition Contractor in Round Rock, TX
Here are the ranges we quote most often for Round Rock projects. A bedroom addition runs $55,000 to $95,000. A sunroom runs $45,000 to $110,000 depending on three-season or four-season build. A full second-story addition runs $180 to $260 per square foot, typically $180,000 to $390,000 total. A bathroom addition runs $40,000 to $85,000, and a bump-out runs $30,000 to $60,000. What moves your number: HOA-required finishes, septic upgrades on older lots, foundation engineering on clay soil, and whether we need a mini-split for climate control. Every project gets a written price before any work starts, and that price doesn’t change once the crew arrives. Call (254) 615-3842 for your exact number.
We Also Serve Cities Near Round Rock
Our crews work throughout the Round Rock area, including Home Addition Contractor in Round Rock, plus Cedar Park, Leander, Austin, and Taylor. If you’re in one of those cities and planning a bedroom, sunroom, or bump-out addition, call us at (254) 615-3842 and we’ll bring the same written pricing and Care Promise to your door.
The Round Rock Playbook for Additions
If you’re adding square footage in Round Rock, the order of operations matters more than the hammer. This is the playbook we use on every job here, and it’s built on years of watching what goes wrong when it’s skipped.
Step one: check your HOA covenants before you dream too far. Teravista, Brushy Creek, and the other master-planned communities all have architectural review committees with their own rules about rooflines, exterior materials, setbacks, and even exterior paint colors. A bedroom addition that doesn’t match the original brick veneer gets rejected. A sunroom with the wrong roof pitch gets rejected. We’ve sat through those reviews, and we know what each committee in Round Rock wants to see before we submit. It saves weeks of back-and-forth.
Step two: check your septic capacity if you’re on the older side of Chisholm Valley or any lot with an original 1980s system. The City of Round Rock will not approve a permit for a second dwelling or an added bedroom if the system can’t handle the load. That means an aerobic system upgrade, which is a real cost, often $15,000 to $25,000 before you even break ground on the addition itself. Neighboring cities with newer sewer infrastructure don’t have this requirement, which is why pricing in Round Rock sometimes surprises people who’ve gotten quotes elsewhere. We flag this before plans are drawn, not after.
Step three: design for clay. Round Rock’s expansive soil is not a preference, it’s a condition. The slab under your addition needs proper drainage, moisture control, and grading. City inspectors check this closely. Pier-and-beam details that work fine in other Texas markets cause cracks and shifting here. We build slab-on-grade with drainage designed for the specific soil report on your lot.
We just finished a bedroom addition for a homeowner in Teravista whose builder-grade HVAC couldn’t handle the extra square footage. Our crew rebalanced the ductwork and added a high-efficiency mini-split for the new room, working around the HOA’s architectural review by keeping the roofline and brick veneer matching the original tract home. That’s how the playbook works: plan for the HOA, the soil, and the systems at the same time, so the finished room feels like it was always part of the house.
Serving Round Rock, TX - Our Local Coverage Area
We’re based in the Round Rock 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 Home Addition Contractor in Round Rock

Yes. Teravista’s architectural review committee must approve your design before construction starts, and building without that approval can trigger a stop-work order and fines. We prepare and submit the specific documentation the Teravista HOA wants, including roofline drawings and exterior finish samples that match the original tract home. It adds time to the front end, but it prevents a halt mid-project. Call (254) 615-3842 and we’ll walk you through the exact submission process for your street.
It depends on the system’s capacity, and in many cases the answer is not without an upgrade. The City of Round Rock will not approve a permit for added plumbing fixtures if the original septic system is already at capacity, and many 1980s Chisholm Valley systems are. An aerobic system upgrade typically runs $15,000 to $25,000 before any addition work begins. We check the system records and current capacity before we quote, so you’re not paying for plans that can’t be permitted. Call (254) 615-3842 for a written price that includes any septic work, if it’s needed.
They are strict about drainage, grade, and moisture control because Round Rock’s expansive clay soil moves with seasonal wet and dry cycles. Inspectors look for proper slab thickness, moisture barriers, and grading that directs water away from the foundation. Plans that skip these details get red-tagged. We engineer slab-on-grade additions for Round Rock soil conditions from day one, with drainage details the inspectors want to see. Call (254) 615-3842 to get a written price that includes the foundation engineering your lot requires.
In most cases, no, if the addition is properly permitted and built to code. Builders in newer Round Rock communities like Teravista generally void warranties only when unpermitted work damages the original structure or systems. The risk is in electrical or roof tie-ins done poorly, not in the addition itself. We pull permits on every project and build to the same code standards the builder used, which protects your warranty. Call (254) 615-3842 and we’ll review your specific warranty terms before any work starts.
Yes. The City of Round Rock requires a building permit for any sunroom addition, and depending on your lot, you may also need HOA architectural approval before the city will issue it. We handle both. The permit process in Round Rock typically moves faster when plans include the drainage and foundation details inspectors expect, which is standard in our written price. Call (254) 615-3842 for a written estimate that includes all permit costs.
Written by Ben Ortega, Owner at Seedling ADU Austin, serving Round Rock and surrounding Central Texas communities.









