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 Prosper
A home addition in Prosper runs $45,000 to $130,000 for a typical room addition, while a detached ADU starts around $90,000 and a garage conversion falls between $30,000 and $80,000. Those numbers move depending on foundation work, code upgrades, and what’s inside the walls once we open them. We’re Barrett & Sons Construction, and we’ve spent 29 years learning how Prosper’s clay soil, post-tension slabs, and rapid-build neighborhoods affect every addition we frame here. Call (877) 610-1318 to talk through your project and get a free estimate.
Why Barrett & Sons Construction Is Prosper’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998, and his sons run the crews. When you call about a room addition in Windsong Ranch or a garage conversion near Star Trail, the person who answers the phone is someone who knows Prosper, not an out-of-state call center. We coordinate scheduling from our Dallas-Fort Worth office, and our crews serve Prosper directly. Our 90-Day Done Right Promise is written on every contract. If something’s not right, one call brings Tom back. That’s why homeowners from Whitley Place to Star Trail keep our number.
Prosper isn’t a place where you can fake local knowledge. Nearly every home here sits on post-tension slabs over blackland prairie clay, and we’ve seen what that clay does to additions framed by contractors who don’t account for it. We pull permits on every eligible job, and we write every price change as a change order before any work proceeds. You’ll know what you’re paying before we cut a single stud. That’s how we’ve earned our reputation across Prosper.
The L.O.C.A.L. values we run on aren’t a marketing slogan. Local roots, On time, Community first, Accountable, Loyal. Tom lives nearby, publishes his license number, and answers his own phone. Ask anyone on your street about us, or look up the license number yourself.
Our Home Additions & ADU Services in Prosper
ADU Design & Permitting
Detached ADUs in Prosper face a specific set of constraints: post-tension slab engineering, city setback requirements, and soil movement that neighboring cities don’t deal with the same way. We handle design, structural drawings, and the full permit package. We also pull the permits ourselves and stand next to the inspection. The permit inspector works for you, not for me, so we like having them involved early. In a town where most homes are 5 to 15 years old, getting the foundation right on a new ADU means understanding how the original slab was designed and how the clay has moved since.
Garage Conversion ADU
A garage conversion ADU in Prosper typically runs $30,000 to $80,000. That range moves with plumbing runs, insulation upgrades, and whether the slab has shifted at the door thresholds, which we check before we quote. Many Prosper garages were built as part of the original post-tension pour, which actually helps, but we still verify the slab profile before framing interior walls. We convert attached garages into livable suites with proper egress, HVAC ties, and finished drywall that won’t crack the first summer the clay dries out.
New Detached ADU
Building a detached ADU in Prosper means pouring a new foundation engineered for expansive clay. We work with local structural engineers who know Collin County soil reports, and we schedule pours early when surface temperatures allow. In July, an unshaded slab in Prosper can hit 120°F, and that changes the curing schedule. We plan for it. A new detached ADU here runs $90,000 to $220,000 by the time the interior is finished, plumbing is stubbed, and the final inspection is signed.
Junior ADU & Interior Conversion
A junior ADU inside an existing Prosper home often makes more sense than a detached build, especially in the large two-story houses common in Whitley Place and Star Trail. We convert bonus rooms, formal dining areas, or oversized utility spaces into private suites with their own entry where the floor plan allows. These projects run the same room addition range of $45,000 to $130,000 depending on square footage, bathroom rough-ins, and whether you need a separate HVAC zone.
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 Prosper
We install brands you can look up, not mystery materials off a van. For ADU kitchens and wet bars, we carry Schluter for waterproofing shower pans and tile substrates. For plumbing fixtures in Prosper garage conversions and junior ADUs, we install Grohe and Sterling. We keep our standard material lists stocked locally so a missing rough-in valve doesn’t stall your finish date. When we quote an ADU or addition in Prosper, the allowance sheet names the exact materials. Scope in writing, allowances in writing, change orders in writing.
Common Home Additions & ADU Problems We See in Prosper Homes
- Post-tension slab movement at interior partition walls. Prosper sits on some of the most expansive clay in the country. Homes as young as 5 to 8 years old already show measurable differential movement, which means any addition we tie into the existing structure has to account for what that slab has already done and what it’ll do in the next drought cycle.
- Undersized framing hidden behind drywall. We recently opened a wall in a Whitley Place home to tie a 400-square-foot room addition into the gable end and found a 12-foot load-bearing header that was undersized and had already cracked the drywall above a transom window. We wrote a change order for the new LVL beam and hurricane ties, held the draw schedule until the city signed off, and closed the wall. The addition went up without a single crack after the first wet season.
- Code upgrades nobody quoted. Prosper’s building code has tightened since most of this housing stock went up. When you open walls for an addition, you trigger requirements for arc-fault breakers, hardwired smoke detectors, tempered glass near stairs, and sometimes updated shear wall details. A contractor who doesn’t know this in advance is pricing you for a surprise.
- Concrete pours scheduled wrong for the heat. Summer surface temperatures on unshaded Prosper slabs regularly pass 120°F. Pouring too late in the day means weakened curing, warped subfloor, and racked exterior walls before the roof is even loaded. We schedule pours early and cure aggressively.
Pricing for Home Additions & ADU in Prosper, TX
Here’s what we see across Prosper for the work we do most in this town. These ranges are specific to Prosper’s labor market and housing stock, not pulled from a national price book.
| Project Type | Typical Range in Prosper |
|---|---|
| Room Addition | $45,000 - $130,000 |
| Garage Conversion ADU | $30,000 - $80,000 |
| ADU Construction (Detached) | $90,000 - $220,000 |
The biggest cost drivers in Prosper are foundation engineering for clay soil, code-triggered upgrades once walls are open, and the labor competition created by all the active spec builds in master-planned communities around town. We write allowances into your contract up front. If an allowance changes, you’ll get a written change order and a signature line before any extra work starts. An allowance that isn’t on paper is a surprise waiting for a date. Call (877) 610-1318 for a free estimate on your addition or ADU in Home Additions & ADU.
We Also Serve Cities Near Prosper
Our crews serve Prosper and the surrounding communities, including Frisco, Celina, Little Elm, and Fairview. If you’re in one of those areas and planning an addition or ADU, we bring the same permit-pulling, change-order-written approach to your project. Our Home Additions & ADU team covers the full metro.
Serving Prosper, TX - Our Local Coverage Area
We’re based in the Prosper 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 Prosper
Post-tension slabs in Prosper move because the blackland prairie clay under them shrinks in summer drought and swells when the rains return, and we’ve measured differential movement in homes as young as 5 to 8 years old. Before we frame any addition onto an existing Prosper home, we check slab profile and look for signs of movement at interior partition walls, door thresholds, and window corners. When we find movement, we write the repair into the scope as a line item before construction starts, not as a change order after the walls are open. Call (877) 610-1318 to talk through what your slab is telling you.
Expect to bring the opened areas up to current code, which in a 2010s Prosper home usually means arc-fault breakers, hardwired interconnected smoke detectors, tempered glass near stairwells and doors, and sometimes shear wall upgrades if you’re opening a large exterior wall. A contractor who doesn’t tell you this before you sign is setting you up for a change order mid-job. We walk the existing structure before we quote, and we write anticipated code upgrades into your contract as allowances so you see the number before demolition starts. Call (877) 610-1318 for an exact quote on your Prosper addition.
We schedule your project with named crews, not whoever shows up, and we order long-lead materials the week your contract is signed so your project doesn’t stall while spec builders around Star Trail and Windsong Ranch are buying up the same framing packages and concrete pours. We also write material allowances at current Prosper market rates, not last year’s price book, so your allowance actually covers what things cost here right now. Call (877) 610-1318 and we’ll walk you through the schedule.
A detached ADU in Prosper needs its own engineered foundation; you don’t tie a new structure onto a post-tension slab that was poured for a different building. We work with local structural engineers who test your soil and design a slab or pier system sized for Prosper’s expansive clay, including the early-morning pours and aggressive curing schedule the summer heat demands here. A new detached ADU in Prosper runs $90,000 to $220,000 depending on size and finish level. Call (877) 610-1318 to get your site evaluated.
Plan for at least one weather delay if your garage conversion runs through spring, because Prosper’s clay holds water and a soaked subgrade can push your concrete work back a week or more. We build that into the schedule up front, and we check existing slab elevation at the garage door threshold before we frame so the finished floor doesn’t bind when the soil dries out and the slab shifts. A garage conversion ADU in Prosper runs $30,000 to $80,000. Call (877) 610-1318 for a free estimate on yours.
Get a Free Estimate on Your Prosper Addition or ADU
Tom Barrett and his sons are on-site most days. We’ve been owner-operated since 1998, and we don’t quote one price and show up with another. Every scope, every allowance, and every price change arrives in writing before work happens. We pull permits and stand next to the inspections. And every job carries our written 90-Day Done Right Promise, plus our permanent 10% Senior & Veteran discount, $40 off any repair over $200, free second opinions on written estimates, and no trip charge inside the county. Call (877) 610-1318 to schedule your free estimate.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Prosper since the company’s founding in 1998.