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 Lewisville
Most home additions and ADUs in Lewisville run between $45,000 and $130,000 for the construction scope, and a detached ADU with its own foundation typically lands between $90,000 and $220,000. The number that actually matters on your lot is driven by something half the contractors quoting Lewisville work never ask about: whether your parcel sits on Blackland Prairie clay, and whether it falls inside a FEMA flood zone for Lake Lewisville. We live with both of those realities on every job in the 75057, 75067, 75077, and 75029 zips, and we price accordingly, in writing, before a single nail moves. Call (877) 610-1318 and we’ll walk your lot with you before we put a number on paper.
Why Barrett & Sons Construction Is Lewisville’s Preferred Home Additions & ADU Company
Tom Barrett started this company in 1998, and his sons run the crews that work Lewisville. That’s not a slogan; it’s who shows up. When a homeowner in the Castle Hills corridor has an HOA architectural-review question, or a family off 3040 needs a variance explained, the person answering that question has pulled a permit in Lewisville before, not in four other states.
Our Home Additions & ADU team approaches Lewisville differently because the ground itself demands it. The Blackland Prairie clay under most of this city shrinks and swells with every wet and dry cycle. A foundation that treats that as an afterthought becomes a crack in the new hallway by year two. We spec post-tensioned engineered foundations as the default on additions here, not as an upgrade line item. It’s the difference between a permit the inspector signs off on and a slab he shakes his head at.
We carry a 90-Day Done Right Promise on every job, written on the contract, not hidden in fine print. If something isn’t done right, Tom comes back and makes it right, one call. Lewisville homeowners have put up with enough surprises from contractors who quote one price and then find the other one. Our crew members are background-checked and uniformed, and a live person answers the phone 24/7 at (877) 610-1318, not a voicemail box and not an out-of-state call center.
Our Home Additions & ADU Services in Lewisville
ADU Design & Permitting
An ADU in Lewisville is not a shed with a bed in it. It’s a permitted dwelling unit, and the permit path runs through the city, plus the U.S. Army Corps of Engineers if you’re near Lake Lewisville. We handle the design, the engineering, the floodplain coordination, and every inspection sign-off. What we will not do is tell you permits are optional. The permit inspector works for you, not for us, and that’s exactly how we like it. A proper ADU design in Lewisville starts with a soils report and a foundation spec that answers the clay question before the drawings go anywhere.
Garage Conversion ADU
Garage conversions in Lewisville run $30,000 to $80,000, but the range isn’t just about finishes. Many of the 1970s to 1990s brick-veneer homes in 75057 and 75067 were built on slabs that have already seen decades of clay movement. Before we convert the garage, we check what the slab is doing now, because framing over a cracked and drifting slab means tearing it out later. We also handle the zoning and set-back review so your conversion doesn’t turn into a code violation with your name on it.
New Detached ADU
A new detached ADU on a Lewisville lot carries the full weight of local requirements: post-tensioned foundation, wind-load framing for Denton County exposure, electrical service upgrade usually, and often dual floodplain permits if your parcel is near the reservoir. We budget the extra 6 to 10 weeks that the Corps Section 404 review adds, because we have watched other schedules stall mid-subfloor when that step got skipped. The structure we build will stand up to a July heat wave and a January ice storm, in that order and often in the same calendar year.
Junior ADU & Interior Conversion
Not every addition needs to be a new building. A junior ADU inside your existing footprint, often a converted primary suite or a finished lower level, keeps you inside the envelope that’s already permitted. In Lewisville, the older ranch homes lend themselves to this well: the floor plans are simple, the interior partitions are not load-bearing, and the existing roof lines give you headroom a second story wouldn’t. We’ll tell you when a junior ADU is the smarter permit path and when a detached unit makes more financial sense for resale.
What happens when you call
- 1
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 Lewisville
We stock and install materials we can put a name behind, because a Lewisville homeowner should be able to look up exactly what’s going into their addition and what it’s rated for. Schluter systems in wet areas, Sterling fixtures where the budget is tight, and GAF roofing and underlayment on any new addition roof. We keep local parts and fast turnaround for Lewisville customers because waiting two weeks on a backordered flashing clip while your new room sits open to a Texas thunderstorm is not acceptable. You can look up every brand we install before you sign anything.
Common Home Additions & ADU Problems We See in Lewisville Homes
- Conventional slabs poured on Blackland Prairie clay. Without post-tensioning, the seasonal shrink-swell cycle cracks the new addition within the first two years. We see it under patio covers, room additions, and garage conversions where someone treated the foundation like it was a Frisco flat lot.
- Lakefront ADU projects stalled mid-subfloor. The owner didn’t budget the extra 6 to 10 weeks for the Army Corps of Engineers Section 404 review alongside the Lewisville floodplain permit. The footing gets poured, then everything stops while the permits catch up. That’s avoidable if the scheduling is done honestly up front.
- Cold-weather concrete curing ignored during a Denton County ice storm. Fresh foundations spall at the edges, and the framing inspection sign-off fails. Crews accustomed to the generic DFW pattern don’t always account for how much more often ice hits the north side of the metro. We do.
- Additions framed without wind-load engineering for the Denton County exposure. A sunroom or second-story addition that wasn’t designed for the rated uplift can rack in a straight-line wind event. The fix afterward is far more expensive than the engineering line item would have been.
Pricing for Home Additions & ADU in Lewisville, TX
Here’s what you should actually expect to pay in Lewisville, with real numbers, not a vague promise of a quote after the first visit.
| Project Type | Typical Lewisville Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
What moves a Lewisville addition within those ranges: whether your lot requires a post-tensioned foundation (most do), whether your parcel triggers floodplain review (near-lake lots usually do), the age and condition of the existing slab if the addition ties into it, and the finish level you choose. A cheap quote that leaves out the engineering and the floodplain coordination is not a better price. It’s an incomplete one. We’ll give you a free written estimate, with every allowance on paper, and we’ll explain every line. Call (877) 610-1318 to schedule yours.
We Also Serve Cities Near Lewisville
Our crews work Lewisville every week, and we also serve the surrounding communities, including Highland Village, Lake Dallas, Flower Mound, and Coppell. If you’re just outside the Lewisville line, the same local knowledge applies, because the clay doesn’t stop at the city limit. Learn more about our service area or call (877) 610-1318 and tell us your cross street.
Serving Lewisville, TX - Our Local Coverage Area
We’re based in the Lewisville 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 Lewisville
Yes, it really does, and it’s not an upsell; it’s what the Blackland Prairie clay under Lewisville demands. Expansive clay shrinks when it dries and swells when it wets, and the seasonal movement here is severe enough that a conventional slab will crack and heave within a couple of years. Post-tensioned engineered foundations are the standard corrective for that condition, and any Lewisville addition quote that skips them is either uninformed or counting on you not to notice until the walls crack. We’ll show you the soils report before we pour. Call (877) 610-1318 for an exact foundation spec on your lot.
Near-lake lots in Lewisville typically trigger a city floodplain development permit and a U.S. Army Corps of Engineers Section 404 or Nationwide Permit review, and sometimes a LOMA review to get the parcel’s flood zone designation right. That combination can add 6 to 10 weeks to your timeline before construction even starts, which is why we plan for it from the first drawing rather than discovering it mid-subfloor. Some builders quote the job without it, then hand you the delay later. We put it in the schedule and the written scope from day one. Call (877) 610-1318 and we’ll check your parcel’s flood status before you commit to anything.
Yes, and they should. Denton County exposure means your addition’s roof and wall assemblies have to meet the engineered uplift and racking numbers in the current adopted code, not the numbers that worked for a patio cover twenty years ago. A compliant quote includes the engineering, the hold-downs, and the strapping details, all of which get inspected. A cheap quote usually leaves the engineering out entirely. The permit inspector signs off on the framing only when those details are right, and that signature is what protects you later, both structurally and for insurance. Call (877) 610-1318 for a quote that includes the wind-load spec in writing.
It often can, because a permitted, inspected addition with an engineered foundation and documented wind-load compliance tells the insurer the structure isn’t a hidden liability. The key word is documented: when your insurer asks what the addition looks like under the drywall, you can hand them the inspection records instead of a story about the guy who did it for cash. Ask anyone on your street, or look up our license number yourself. A paper trail on the permit and the inspections is worth real money when the policy renews. Call (877) 610-1318 and we’ll walk you through what the paperwork will include.
You put every allowance and every price change in writing before work happens, and you work with a contractor whose default is the written change order rather than the verbal “we’ll sort it out later.” An allowance that isn’t on paper is a surprise waiting for a date. In Lewisville, where foundation and floodplain discoveries can shift the scope, that paper trail matters even more. We issue a written change order before any scope change touches the job, and we do not proceed until you’ve signed it. Call (877) 610-1318 for a quote you can hold us to, on paper.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Lewisville since 1998.