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 Harlingen
Most people in Harlingen don’t want to build a second home on their lot. They want their adult daughter and grandkids to have a place nearby, or they want a rental unit that pays the note, or they’re done climbing stairs and need a first-floor suite. A home addition or ADU in Harlingen typically runs $45,000 to $130,000 for additions, and $90,000 to $220,000 for a full detached ADU, with garage conversions landing between $30,000 and $80,000. We’re Barrett & Sons Construction, and we’ve spent nearly three decades building on the black clay that makes this city’s foundations move more than any contractor from up north expects. Call us at (877) 610-1318 and we’ll talk through what your lot can actually handle.
What makes Harlingen different isn’t the heat. It’s the ground. The montmorillonite clay under the 78550 and 78552 ZIP codes swells and shrinks with every drought and every rain, and any addition poured on a conventional slab without post-tension cables is going to crack. That’s not speculation. We see it in the corner cracking and door-frame racking on pre-1980s homes across the city. Before we draw a single line for your ADU, we look at what your existing foundation is doing, because tying a new structure to a shifting slab is how you turn a $90,000 project into a $140,000 repair.
Why Barrett & Sons Construction Is Harlingen’s Preferred Home Additions & ADU Company
Tom Barrett started this company in 1998, and his sons run the crews. When you call about a new detached ADU in Harlingen, the person who answers is a live person, day or night, not a call center reading from a script. Tom publishes his name, his address, and his license number. Look them up before you sign anything. That’s the point.
Harlingen homeowners ask us the same question: “Will the price change once work starts?” Our answer is on paper. Every scope, every allowance, every change order arrives in writing before a single nail moves. The allowance that isn’t on paper is a surprise waiting for a date. We don’t do surprises. And when the job is done, it’s backed by the 90-Day Done Right Promise, written on every contract. If something isn’t done right, one call brings Tom back.
We know the local realities that national companies miss. A second-story addition in a CMU block house built in the 1960s needs different tie-in work than a modern frame home off Dixieland Road. A garage conversion in a Winter Texan neighborhood near Stuart Place means working around seasonal absence and deferred maintenance. These aren’t edge cases here. They’re the normal Tuesday.
Our Home Additions & ADU Services in Harlingen
ADU Design & Permitting
Harlingen sits in a wind-borne debris hurricane zone, so every ADU needs wind-load compliance that somebody from Dallas or Austin might not think twice about. We handle design, engineering, and all permitting with the city. The permit inspector works for you, not for us, and we want him on your job. Every eligible project gets permits pulled and inspections signed. Call (877) 610-1318 to start drawings.
Garage Conversion ADU
Plenty of Harlingen homes have attached garages that bake in the South Texas sun half the year and store almost nothing. Converting one into a rentable unit or a mother-in-law suite usually runs $30,000 to $80,000. The big variable isn’t finish level. It’s whether the existing slab was poured with post-tension reinforcement and whether the garage shares a wall with the main house. We’ve converted garages in neighborhoods across the 78551 area, and every one starts with a foundation inspection, not a sledgehammer.
New Detached ADU
This is the big one for Harlingen families who want a separate structure in the backyard. At $90,000 to $220,000, a new detached ADU is a serious decision, and the soil under the footprint will determine the foundation design more than any other single factor. We specify post-tension slab systems as standard, because conventional slabs on this clay will move. It’s not an upgrade. It’s the only way to build here.
Junior ADU & Interior Conversion
Not every household needs a full kitchen. A junior ADU, often a bedroom with a kitchenette and private entrance carved from existing square footage, gives an aging parent independence without the cost of new construction. Interior conversions avoid foundation questions entirely, which appeals to owners of older homes in the 78552 ZIP code who don’t want to disturb a settled slab. We’ll tell you honestly whether a conversion or an addition makes more sense for your floor plan.
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 Harlingen
If we’re putting windows in your new ADU or sunroom, you’ll get names you can look up. We install Simonton, Ply Gem, PGT, and CGI products, and PGT’s impact-rated lines matter here in a wind-borne debris zone. Southern exposures off any east-west street in Harlingen take brutal UV, and cheap vinyl frames chalk and warp within a few years. We’d rather install a PGT or CGI window once than replace a bargain twice. If you’re adding a sunroom or wrapping an enclosed patio, ask us which glass package makes sense for your orientation.
Common Home Additions & ADU Problems We See in Harlingen Homes
- Slab movement under the existing house. The clay beneath Harlingen can move two to four inches vertically between a dry summer and a wet winter. Older slabs without post-tension cables show corner cracking, and any addition tied to them without a proper isolation joint will crack along with them.
- Pipes in exterior walls. Harlingen houses were built for subtropical weather, which is why Winter Storm Uri in February 2021 caused so many failures. When we open a wall for an addition or conversion, we check what’s running through it and bring insulation and pipe placement up to a standard that can survive a freeze nobody expected.
- Heat and UV degradation. Sustained 95 to 100°F summers and intense sun break down roofing, sealants, and exterior finishes faster than almost anywhere else in the country. Rooflines and tie-ins for additions need materials rated for this climate, not whatever the big-box store has on the shelf.
- Deferred maintenance in vacant homes. Winter Texans leave for months, and problems bake undetected. We regularly walk into Harlingen garage conversions where a seal failed in June and nobody noticed until November. Part of our job is finding what’s been quietly failing before we build on top of it.
Pricing for Home Additions & ADU in Harlingen, TX
We also handle Kitchen Remodeling in Harlingen and Bathroom Remodeling in Harlingen, so if your addition includes a new kitchen or bath, one crew handles the whole job.
We Also Serve Cities Near Harlingen
Our Home Additions & ADU work reaches every corner of Harlingen and beyond. We serve San Benito, La Feria, Mercedes, and Progreso, and the same crews, the same written change orders, and the same 90-Day Done Right Promise apply in every one of them. No trip charge inside the county.
Serving Harlingen, TX - Our Local Coverage Area
We’re based in the Harlingen area and know this community well - from Harlingen Roofing to full remodels. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Home Additions & ADU in Harlingen
A room addition in Harlingen runs $45,000 to $130,000, a detached ADU runs $90,000 to $220,000, and a garage conversion runs $30,000 to $80,000. Foundation work on Harlingen’s expansive clay is the single biggest variable, which is why we walk the lot before we quote. Call (877) 610-1318 for a free estimate with exact numbers.
After permits are approved, most Harlingen additions and ADUs take four to eight months from groundbreaking to final inspection, depending on size and foundation work. Design and permitting usually add six to ten weeks. We’ll give you a written schedule before work starts.
Yes, on every eligible job. Harlingen sits in a wind-borne debris hurricane zone, and wind-load compliance is not optional. We pull all permits and schedule all inspections, and the inspector works for you, not for us.
A garage conversion in Harlingen runs $30,000 to $80,000, while a new detached ADU runs $90,000 to $220,000, and Windows & Doors - Harlingen upgrades can be bundled into either project. The conversion wins on cost because the shell already exists, but the existing slab condition determines whether it’s actually a bargain. Call (877) 610-1318 and we’ll inspect the slab before you commit to anything.
Yes. Every job we complete in Harlingen carries the 90-Day Done Right Promise in writing. If something isn’t done right, one call brings Tom Barrett back to make it right. No fine print, no runaround.
Call Barrett & Sons Construction for Your Harlingen Home Addition or ADU
If you’re thinking about an addition or ADU on your Harlingen lot, start with a conversation, not a contract. Call (877) 610-1318. A live person answers. We’ll ask about your house, your soil, your family’s needs, and we’ll tell you straight what this is going to cost and what could go wrong. Free estimates, written change orders, permits pulled, and a promise in writing. That’s how Tom Barrett has done it since 1998, and that’s how his sons do it now.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Harlingen and the Rio Grande Valley.