A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable ADU Builders Across Alamo Heights
ADU construction in Alamo Heights typically runs $180,000 – $420,000 for a detached unit and $120,000 – $240,000 for a garage conversion or attached addition. That’s a wide spread because Alamo Heights brings something most San Antonio neighborhoods don’t: a separate zoning ordinance, a 40% lot coverage cap, and a design review process that actually reads your elevation drawings. If you’re researching ADU Builders who understand how that process works before the first concrete pour, call Benson ADU San Antonio at (430) 258-2928. We write the price before we start, and we don’t surprise you after the walls come open.
Why Benson ADU San Antonio Is Alamo Heights’s Preferred ADU Builders Company
Homeowners in Alamo Heights tend to ask sharper questions than most. They know their house was built between the 1920s and 1950s. They know the clay soil moves. They know a permit might trigger electrical upgrades they didn’t plan for. That’s exactly the conversation our ADU Builders team is built to have. We don’t hand you a verbal number and hope for the best. We inspect first, then price the real scope, including the code upgrades a 1948 house will require once the walls are open.
Troy Eastman, who leads our team, has a straightforward rule: if a surprise is coming, the homeowner hears about it in writing before it becomes a line item. That’s why Alamo Heights customers stick with us. They’ve been through contractors who quote low, open the wall, and then send a change order that doubles the budget. We write allowances into the contract for exactly that scenario, and any change gets a written price and your approval before we move.
Our response time to Alamo Heights is typically same-week for initial consultations and site evaluations. Crews dispatch from our San Antonio office and serve Alamo Heights locally. Every technician is background-checked and arrives in uniform, so you know exactly who’s walking onto your property on Cambridge Oval or along Arcadia Place. And when you call, a live person answers. Always.
ADU Construction in Alamo Heights
ADU Construction in Alamo Heights means building a livable secondary unit on a lot that was platted when cars were narrower and houses sat deeper. The work involves foundation design suited to expansive clay soil, framing or panelized construction, full electrical and plumbing runs, insulation rated for hot humid summers, and exterior finishes that pass the city’s architectural compatibility review. A homeowner here needs this when a garage conversion, backyard cottage, or attached addition becomes the most practical way to house family or generate rent without leaving the neighborhood.
A site-built detached ADU in Alamo Heights generally runs $280,000 – $420,000 depending on size, foundation work, and the level of architectural detailing the design review board expects. A garage conversion lands between $120,000 and $180,000 when the existing structure is sound; if the garage has foundation issues or knob-and-tube wiring, the number moves up. We give you that range in writing before you commit.
Permit Triggers and the Real Cost of Opening Walls
Here’s what most contractors won’t tell you upfront: in Alamo Heights, pulling a permit on a 1930s or 1940s house means the inspector will look at more than the ADU. If the existing service panel is undersized, you’re upgrading it. If the wiring is original, you’re rewiring. If the sill plates are rotted, you’re sistering framing. We plan for that in the estimate, not after demo day.
Foundation Work on Expansive Clay
The clay soil under Alamo Heights expands when wet and contracts when dry. That movement cracks slabs and pulls foundations apart over decades. Any new ADU needs either a properly engineered slab on grade with moisture barriers or a pier-and-beam system that can flex. We bring in a geotechnical review on every project and price the drainage system as a required line item, not an extra.
Detached ADU in Alamo Heights
Detached ADU construction in Alamo Heights is the most requested project type we quote, and it’s also the one most likely to hit the city’s 40% lot coverage cap. A detached unit means a separate structure with its own foundation, walls, roof, and utility connections, typically 400 – 800 square feet. Homeowners pursue this when they want true separation from the main house, whether for an aging parent, a tenant, or a quiet workspace.
A 600-square-foot detached studio ADU in Alamo Heights typically costs $240,000 – $320,000. A one-bedroom unit with a full kitchen and bath runs $300,000 – $420,000. The spread comes from foundation requirements, utility trenching distance, and the level of stucco, tile, and trim work needed to satisfy the architectural compatibility standard.
Working Within the 40% Coverage Rule
Alamo Heights caps total building coverage at 40% of the lot. A 1950s ranch on a 7,500-square-foot lot with a 2,200-square-foot house and a 400-square-foot garage is already at 34.6%. Add a 600-square-foot detached ADU and you’re over. That’s a variance situation, and we handle the application, drawings, and hearing prep. We’ve done enough of them to know what the board pushes back on and how to design around it.
What the Design Review Actually Checks
The city requires detached ADUs to be architecturally compatible with the main house. On a Spanish Colonial Revival home near Broadway, our crew opened the garage to find original knob-and-tube wiring brittle at every junction and sill plates rotted by decades of gutter overflow against the clay soil. We rewired the entire ADU to current code with a new subpanel, sistered the damaged framing, and flashed the foundation with a drainage mat before closing walls, each change priced in writing before we touched it. That’s the job, done honestly.
Trusted Brands We Service in Alamo Heights
We’re authorized to build with prefab and panelized systems from Boxabl, Plant Prefab, Tuff Shed, and James Hardie cladding products. For Alamo Heights specifically, panelized construction often makes sense because it shortens on-site build time and reduces disruption on tight lots where staging space is scarce near Broadway and Nacogdoches Road. We stock the most common materials for these systems locally, so a replacement panel or trim match doesn’t mean waiting two weeks for a freight order. Homeowners can research these brands independently, which is exactly how it should be.
Common ADU Builders Problems We See in Alamo Heights Homes
- Knob-and-tube wiring hiding behind original plaster. Most 1920s – 1950s homes in Alamo Heights still have at least one active circuit of it. Opening walls for an ADU conversion triggers a code requirement to address it, and rewiring a 1,500-square-foot house can run $18,000 – $35,000 before you ever hang drywall on the ADU itself.
- Design rejection due to the 40% coverage cap. We’ve walked into homes where a previous contractor drew a detached ADU that put the lot at 43% coverage and the owner didn’t learn it until the city stamped “denied.” Getting a variance takes 6 – 10 weeks and costs $1,500 – $4,000 in fees and drawings, so we check coverage math before we draw anything.
- Clay soil movement cracking fresh foundations. Without proper drainage and a moisture barrier, a new slab in Alamo Heights can show hairline cracks after the first wet-dry cycle. We install drainage mats and perimeter drains on every foundation, and we price it in the original quote.
- Rot at the sill plate from gutter overflow. Decades of downspouts dumping water against the foundation rots the wood where the wall meets the slab. If you’re converting a garage, that rot is load-bearing. We sister on new framing and flash the joint before any finish work.
Pricing for ADU Builders in Alamo Heights, TX
Here are the numbers we quoted in Alamo Heights in the last twelve months. Garage conversion with new subpanel and full rewire: $140,000 – $180,000. Attached ADU addition of 400 square feet: $160,000 – $220,000. Detached studio with bath and kitchenette: $210,000 – $280,000. Detached one-bedroom with full architectural compatibility detailing: $320,000 – $420,000. What moves the number most in this city is the existing electrical service, the foundation condition, and whether you need a coverage variance. The way we handle it: you get a written quote with allowances for the unknowns. If an allowance gets used, you approve it in writing first. Call (430) 258-2928 and we’ll schedule the free site evaluation.
We Also Serve Cities Near Alamo Heights
Our team handles ADU projects across the broader San Antonio metro, including ADU Builders in Alamo Heights, San Antonio proper, Schertz, Live Oak, and Leon Valley. The permit rules change at each city line, and we track those differences so you don’t have to. If you’re on the edge of Alamo Heights or just outside it, call and we’ll tell you which jurisdiction you’re in and what it means for your project.
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 About ADU Builders in Alamo Heights
Yes. Alamo Heights’s zoning ordinance requires accessory dwelling units to be architecturally compatible with the primary residence, which typically means matching rooflines, exterior materials, window proportions, and overall style. On a Spanish Colonial Revival home, that means stucco, clay tile, and deeply recessed windows. On a Craftsman bungalow, it means wood siding details and bracketed eaves. We prepare elevation drawings that meet the design review standard before filing, which dramatically reduces rejection risk. Call (430) 258-2928 if you want to know whether your planned ADU will pass before you spend money on drawings.
Opening walls on a pre-1955 house triggers electrical, structural, and sometimes plumbing code reviews of the connected existing structure. If the inspector finds knob-and-tube wiring, you must address it. If the framing is undersized or rotted, you must fix it. If the panel is undersized, you must upgrade it. We write these as allowances in the contract, and every allowance has a pre-priced scope attached. You’ll know the worst case before we ever open the wall. Estimates are free, and so is the first conversation.
We measure your lot, your existing house footprint, the garage, any covered patios, and any accessory structures. If the total exceeds 40% of the lot area, a variance is required. The math is simple; it’s the variance process that gets complicated. We run the coverage calculation for free during the initial site visit and tell you the same day whether your project fits or needs board approval.
Yes. We prepare the site plan, coverage calculation, elevation drawings, and variance application package, and we attend the board hearing with you. Alamo Heights variances for ADUs typically take 6 – 10 weeks and cost $1,500 – $4,000 in application fees and preparation work. We’ve handled them for detached ADUs between Arcadia Place and Patterson Avenue, and we know what the board wants to see.
Maybe. Alamo Heights requires architectural compatibility with the main house, so a standard Tuff Shed shell won’t pass design review on most lots unless we substantially modify the exterior. A Boxabl or Plant Prefab panelized unit comes closer, but we typically need to add stucco, a compatible roofline, and trim details to satisfy the standard. The best approach is to pick the prefab brand you’re interested in, bring us the lot and the main house photos, and we’ll tell you honestly whether it’ll pass or what it takes to get it there. Call (430) 258-2928 and we’ll walk you through it.
Get Your Alamo Heights ADU Priced in Writing
You deserve a real number, not a handshake and a maybe. If you’re planning a detached ADU, garage conversion, or attached addition in Alamo Heights, call Benson ADU San Antonio at (430) 258-2928 or schedule a free site evaluation. We’ll walk your lot, run the coverage math, check the panel and the wiring, and give you a written price that includes the code upgrades your house will actually need. No surprises after the walls come open. Just the number, in writing, before we start.
Written by Troy Eastman, Owner at Benson ADU San Antonio, serving Alamo Heights and the surrounding metro.
