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 Alamo Heights
A home addition or ADU in Alamo Heights typically runs $45,000 to $130,000 for a room addition and $90,000 to $220,000 for a detached ADU, with garage conversions landing between $30,000 and $80,000. Those numbers assume the work is permitted through Alamo Heights City Hall, not San Antonio or Bexar County, which is where most surprises start. Barrett & Sons Construction has been doing additions and ADUs in Alamo Heights long enough to know the difference between what a contractor promises and what an older 78209 home actually gives up once the walls come open. Call (877) 610-1318 and Tom Barrett will talk you through what your project really involves before you spend a dime.
Why Alamo Heights Trusts Barrett & Sons for Additions and ADUs
Alamo Heights is not San Antonio. It runs its own building department on Austin Highway, and every permit for a room addition, garage conversion, or backyard ADU gets pulled through Alamo Heights City Hall. We know the inspectors there by name. We know they schedule differently than the county. We know they look hard at tie-ins to older framing and foundations. That local knowledge is the difference between a project that cruises through inspections and one that sits under a stop-work order while the homeowner wonders what happened.
We’re an owner-operated company founded in 1998. Tom Barrett’s name is on the truck, on the contract, and on the license you can look up before you sign. His sons run the crews. When we quote a home addition in Alamo Heights, the scope arrives in writing, every allowance is on paper, and any change gets priced and approved before a single nail moves. Homeowners in their 50s, 60s, and 70s who have been burned by a national outfit that quoted one number on the phone and billed another at the door tend to appreciate that.
And when a Tudor Revival in the 78209 zip code opened up a wall for a room addition last spring, our crew found original knob-and-tube wiring and a load-bearing header someone had notched decades ago. We pulled the Alamo Heights permit, wrote a change order for the rewiring and structural repair, and got the city’s inspection sign-off before closing the wall. No surprises at the punch list. That’s how we work.
Our Home Additions & ADU Services in Alamo Heights
ADU Design & Permitting
Building an ADU in Alamo Heights starts long before a shovel hits dirt. Because the city is an independent municipality entirely surrounded by San Antonio, the permit goes through Alamo Heights City Hall on Austin Highway, not the San Antonio portal. We handle the drawings, the zoning check, the soil evaluation, and every inspection booking so you’re not chasing paperwork. Alamo Heights inspectors apply their own interpretations of the IRC to older, non-conforming lots, which means a design that works elsewhere may need adjustments here. Our Home Additions & ADU team knows what triggers a deferral and what gets approved.
Garage Conversion ADU
Detached garages in Alamo Heights are frequently original to 1920s through 1950s homes. Many sit on slabs that have moved with the expansive clay, and most were never waterproofed or insulated for living space. Converting one to an ADU usually means foundation assessment first, then moisture management, then the build-out. In Alamo Heights, garage conversions commonly land between $30,000 and $80,000 depending on whether we’re adding a bathroom, a kitchenette, and a separate meter for utilities. We write the foundation contingency into the contract, on paper, before we start.
New Detached ADU
A new detached ADU in Alamo Heights is a serious investment, typically $90,000 to $220,000 all-in with permits, site work, utilities, and finishes. The biggest variable here is the soil. San Antonio’s montmorillonite clay runs directly under Alamo Heights, and the summer-drought then fall-rain cycle causes slabs to heave and settle. We design foundations with the drainage and soil-moisture management those conditions demand, not what a tract builder would pour in a suburb. If the city requires a soils report, we pull it and design to it.
Junior ADU & Interior Conversion
A junior ADU converts existing interior space, often a portion of a ranch or a second-story room, into a self-contained unit with a separate entrance and small kitchen. Because these projects touch existing framing in homes built between the 1920s and 1950s, we see lath-and-plaster walls, undersized headers, and floor systems that have shifted over the decades. We plan for those realities up front. The scope of work includes allowances for hidden knob-and-tube, notched structural members, and framing that no longer meets code the moment we open the wall.
We also handle room additions, second story additions, sunrooms and enclosed patios, and ADU site prep and utilities. Each one gets the same treatment: inspection first, allowances in writing, and every price change approved on paper before work proceeds.
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 Install in Alamo Heights
When you add onto a home in Alamo Heights, the windows and doors you choose have to match the architectural character of the original house. We install Simonton windows for their clean profiles and durability in the Texas heat. For impact-rated projects or homes with specific wind-load requirements, we use PGT and CGI. These are brands you can look up, not mystery products off a van. We stock the common sizes and hardware for Alamo Heights jobs, which keeps lead times short and lets us order the right units the first time rather than guessing at rough openings.
Common Home Additions & ADU Problems We See in Alamo Heights Homes
- Permits pulled from the wrong jurisdiction. Alamo Heights has its own inspections office on Austin Highway, separate from San Antonio and Bexar County. A contractor who files through the San Antonio portal gets a stop-work order. We file every Alamo Heights permit through Alamo Heights City Hall, period.
- Hidden knob-and-tube wiring and notched framing. Homes built in the 1920s through 1950s carry original electrical systems and structural modifications that never met code. Opening a wall for a room addition reveals these conditions. Our contracts carry written allowances so the price doesn’t blow up mid-project and force you to fight every change order.
- Expansive clay soil movement. The montmorillonite clay under Alamo Heights swells in wet months and shrinks in drought. Pier-and-beam homes shift, slabs crack, and drainage grading becomes a structural issue. Nearly every addition or ADU we build here includes soil-moisture management and drainage correction as part of the scope.
- Historic structure requirements. Alamo Heights inspectors treat additions to non-conforming historic structures with extra scrutiny, particularly around setbacks, rooflines, and matching materials. If your home is a Tudor Revival or Spanish Colonial Revival, the addition has to respect the original massing. We have done enough of these to know what the city will accept before we draw final plans.
Pricing for Home Additions & ADU in Alamo Heights, TX
On this page, we give you the real market ranges for Home Additions & ADU in Alamo Heights. These are not national averages. They reflect what older homes in the 78209 actually cost when you factor in Alamo Heights permits, hidden conditions in 1920s to 1950s construction, and the soil work the clay demands.
| Project Type | Typical Range in Alamo Heights |
|---|---|
| Home Addition | $45,000 – $130,000 |
| ADU Construction | $90,000 – $220,000 |
| Garage Conversion | $30,000 – $80,000 |
What moves the number? Foundation condition, the amount of hidden electrical and framing work the existing structure forces on us, whether the project triggers historic review, and the finish level you choose. We write every allowance into the contract before we start, and if a surprise shows up after the wall is open, you get a written change order with the price before we spend a dollar of your money. Call (877) 610-1318 for a free estimate with line-item pricing.
We Also Serve Cities Near Alamo Heights
Our Home Additions & ADU team works throughout the Alamo Heights area and into the surrounding communities. We’re scheduling additions and ADUs in Terrell Hills, San Antonio, Windcrest, and Kirby right now. If you live nearby and want the same permit-first, written-change-order approach, call (877) 610-1318.
Serving Alamo Heights, TX - Our Local Coverage Area
We’re based in the Alamo Heights 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 Alamo Heights
Every ADU in Alamo Heights must be permitted through Alamo Heights City Hall on Austin Highway, not through the City of San Antonio’s portal and not through Bexar County. Alamo Heights operates its own building department with its own inspectors and scheduling system. A contractor who files in the wrong jurisdiction will get a stop-work order. We pull Alamo Heights permits exclusively. Call (877) 610-1318 to confirm your project’s permit path.
The most common hidden issues are knob-and-tube wiring, load-bearing headers that have been notched, lath-and-plaster walls that crumble when opened, and foundation movement from the expansive clay soil. Homes from the 1930s and 1940s were built before modern framing standards, so we carry written allowances for rewiring, structural repair, and plaster remediation in every contract. That way, the price is agreed before the wall is opened, not argued after. For an exact scope, call (877) 610-1318 for a free estimate.
Alamo Heights inspectors apply their own interpretations of the IRC to additions on historic and non-conforming structures, with extra attention to roofline compatibility, setbacks, and material matching. They review these projects individually rather than applying a blanket suburban standard. We have built enough additions on Tudor Revivals and Spanish Colonial Revivals in the 78209 to know what will pass before we draw final plans. Call (877) 610-1318 and we’ll walk your project through the review process.
Most detached garages in Alamo Heights sit on slabs that have moved with the clay soil and were never designed for living space, so the foundation usually needs assessment and often reinforcement or drainage work before conversion. Skipping that step leads to cracked walls, moisture problems, and an inspection failure. We evaluate the slab first and write any foundation contingency into the contract, in writing, before we start. Get a free evaluation by calling (877) 610-1318.
Alamo Heights additions cost more because the city runs its own permitting and inspection process, the housing stock is older and carries hidden electrical, structural, and plaster conditions, and the expansive clay soil demands foundation and drainage work that newer subdivisions rarely require. You are also paying for a contractor who knows the Alamo Heights building department and shows up with the right permits the first time. Our quotes carry line-item allowances for those realities, not vague contingencies. For a written estimate, call (877) 610-1318.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Alamo Heights with permit-first home additions and ADUs.