A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted Room Addition Contractor for San Antonio Homeowners
Room addition costs in San Antonio typically run between $180 and $340 per square foot for site-built construction, while prefab and modular options can bring that down to $120 to $220 per square foot depending on finishes and foundation work. That’s a wide band, and the number shifts with site access, soil conditions, and whether you choose a panelized system from a brand like Plant Prefab or a traditional stick-built addition. Benson ADU San Antonio has been building additions and ADUs since 2006, and we put every price in writing before a single shovel turns. Call Troy and the team at (430) 258-2928 to get a line-item estimate you can actually compare against other bids.
Most San Antonio homeowners call us when the house stops fitting the life inside it. A second kid. An aging parent. A remote job that needs a real office, not a corner of the dining room. We’ve built additions in Alamo Heights, Windcrest, and Castle Hills, and the conversation always starts the same way: what’s the real cost, what’s the timeline, and which Room Addition Contractor in San Antonio is showing up at my door. We answer all three in the first call.
Key Takeaways:
- The Relay Visibility Guarantee means a written price before work starts, a 365-Day Done Right Promise, and a free second visit if any covered repair fails.
- We build with researched, name-brand prefab systems: Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie cladding.
- Every technician is background-checked and wears a Benson uniform, and a live person answers the phone 24/7.
- Owned and operated by Troy Eastman as part of the Relay Home Co. family, founded 2006.
Sunroom Builders
Sunroom builders in San Antonio design and construct glass-focused room additions that flood a home with natural light without the full cost of a traditional extension, and that cost here typically lands between $150 and $280 per square foot when basic framing, glazing, and a foundation are included. A sunroom makes the most sense when you want a reading nook, a bright dining area, or a flex space that feels outdoorsy but stays climate-controlled. Benson ADU San Antonio handles the full scope: foundation, framing, glazing, HVAC tie-in, and the finish work, with a written price before we order a single window.
Foundation and Framing Choices
San Antonio’s clay-heavy soil moves with the seasons, and a sunroom foundation has to account for that. We pour slab-on-grade or install pier-and-beam depending on your lot, and we spec the frame for San Antonio’s wind load requirements, not a generic formula.
Glazing Packages and Finish Costs
Low-E insulated glass keeps a Texas summer sunroom from turning into a greenhouse. Expect glazing upgrades to add $30 to $60 per square foot over standard panels, and we’ll show you the payback on cooling costs before you commit.
Room Additions
Room additions in San Antonio are the broadest category we build: a new bedroom, a second living area, a home office, or a dining room bump-out, generally priced between $180 and $340 per square foot for site-built work from a Room Addition Contractor - Converse team like ours. You need a room addition when your family has outgrown the original floor plan and moving isn’t the right financial call. Benson ADU San Antonio provides a written, line-item price before work begins, and that price does not change unless you change the scope.
Tying Into the Existing Structure
The hardest part of any room addition is the transition where old roof meets new roof and old slab meets the new pour. We detail that connection point on every plan set and walk you through it, so there are no mystery line items in the estimate.
Permitting and Setback Reality
Most San Antonio neighborhoods have setback rules that dictate how close you can build to property lines. We measure the lot, check the plat, and flag any variance risk in the first conversation, not at the foundation inspection.
Modular Home Addition
Modular home addition pricing in San Antonio ranges from $120 to $220 per square foot, because modules are built in a controlled factory environment and then set on your site, which trims labor days and weather delays. This is the right choice when speed matters and you want factory-precision framing with less on-site noise. Benson ADU San Antonio is authorized to build with Plant Prefab, Boxabl, and other panelized systems, and we give you curated options instead of one take-it-or-leave-it product.
Factory Tolerance vs. Site Tolerance
Factory-built modules are assembled to tighter tolerances than most site framing, which matters for finish quality on drywall and trim. The trade-off for a homeowner is fewer customization changes after the order, so we front-load design decisions in a structured, easy sequence.
Site Prep and Crane Access
Modular additions need clear crane access and a stable setting pad. We survey the site early and confirm access width, overhead lines, and soil bearing, because a surprise on set day is the one surprise you never want to pay for.
Home Addition Plans
Home addition plans in San Antonio typically cost between $2,500 and $8,000 for a full permit-ready drawing set from a licensed designer or draftsman, which is a line item Benson ADU San Antonio includes transparently in your written estimate. Good plans prevent the two things that sink additions: permit rejections and scope creep. We produce or manage a full plan set: floor plan, foundation, roof framing, electrical, and a written scope of work that matches the drawings line by line.
What a Real Plan Set Includes
A legitimate plan set for a San Antonio addition includes site plan, foundation plan, framing plan, and electrical layout. If a contractor hands you a one-page sketch and calls it a plan, walk away. We don’t operate that way.
Design Decisions That Move the Price
Vaulted ceilings, extra windows, and plumbing additions each add real cost. We build a design session around what you value versus what quietly inflates the price, so you decide with numbers in front of you.
In Law Suite Builders
In law suite builders in San Antonio construct self-contained living spaces with a small kitchen or kitchenette, a bath, and a private entrance, typically priced between $200 and $350 per square foot when built as an attached addition. An in-law suite is the answer when a parent or adult child moves in and needs both proximity and privacy. Benson ADU San Antonio builds these to code with separate access, its own HVAC zone, and sound isolation at the shared wall, and we give you a written price on the full scope.
Accessibility and Aging in Place
If the suite is for an aging parent, we discuss door widths, zero-threshold showers, and grab-bar blocking early. Retro-fitting those features after drywall is up costs three times as much, and we’d rather get it right the first time.
Kitchenette or Full Kitchen?
San Antonio zoning treats a full kitchen differently from a kitchenette, and that distinction changes permitting. We’ll explain the local ordinance plainly and design the suite to meet your family’s actual need, not a generic template.
ADU Conversion
ADU conversion pricing in San Antonio usually lands between $120 and $250 per square foot when you are converting an existing garage, shed, or other structure into a legal accessory dwelling unit. This is the best path to rental income or a guest suite when you already have a structure that can be brought to code. Benson ADU San Antonio handles the complete conversion: insulation, electrical, plumbing, egress, and finish, with a written price and a 365-Day Done Right Promise stamped on the project.
Garage Conversion Economics
Garage conversions typically cost less than ground-up ADUs because the shell, slab, and roof are already there. But they still need new electrical service, insulation, and proper egress, and we price all of that out in the first written estimate.
What Makes a Conversion Legal
A legal ADU conversion in San Antonio requires permitted work and a final inspection, not just drywall and a window unit. Unpermitted conversions become a problem at resale and with insurance, and we won’t build one that isn’t fully permitted.
Brands We Service
We work with Boxabl systems regularly for ADU conversions and compact additions. Boxabl’s folding panel design means less crane time on site, and we spec the foundation and utility hookups to match the factory tolerances exactly. That matters in San Antonio’s shifting clay soil, where a mismatched pad causes door binding within the first year.
Plant Prefab is another brand we recommend for San Antonio homeowners who want a greener, panelized build. Their panels arrive pre-cut and pre-drilled, which reduces on-site waste and shortens the framing window. We also use James Hardie cladding on both prefab and site-built additions, because San Antonio humidity and sun punish cheap siding fast. Whether you have a specific brand in mind or want us to compare options with real numbers, Benson ADU San Antonio can help you decide.
Signs You Need a Pro Right Now
- Cracks spreading across the ceiling or walls near the proposed addition area. These can signal foundation movement in San Antonio’s expansive clay soil, and a poor addition design can make it worse. A professional assessment before you build is cheaper than structural repair after.
- Roof leaks where a previous addition was tied in. The old-roof-to-new-roof junction is a frequent failure point. If water is getting in, the flashing job was rushed or installed without step flashing, and it needs professional correction before framing begins.
- Doors sticking or gaps widening around existing window frames. Humidity swings in San Antonio stress framing and trim. A knowledgeable contractor will check for structural movement before adding weight to any wall.
- Any unpermitted addition or conversion on the property. If a previous owner built something without permits, you may be sitting on a liability that affects your insurance and resale. We can assess what’s salvageable and what needs to come out.
- Electrical panel at capacity. A room addition or ADU often requires a panel upgrade or a subpanel. If your panel is already maxed out, any competent addition plan has to account for that cost from day one, not when the electrician discovers it mid-project.
Our Process, Step by Step
- 1
Initial call and rough budget. You reach a live person, not a voicemail. We ask about your goals, the structure, and the lot, and we give you a real price range based on similar San Antonio projects before we ever schedule a site visit.
- 2
On-site walkthrough and measurements. We measure the existing structure, check the soil and access, and document everything with photos. This is also when we flag setback, easement, or HOA concerns specific to your neighborhood.
- 3
Written line-item estimate. You get a written price with every cost category spelled out: foundation, framing, roofing, electrical, plumbing, finishes, permits. If the number changes later, it’s because you changed the scope. We put that in writing too.
- 4
Permit-ready plans and submission. We coordinate the full drawing set and handle the San Antonio permit submission. You’ll know exactly what the city has approved and when inspections are scheduled.
- 5
Build, photo updates, and final walkthrough. Uniformed, background-checked technicians handle the build, and you get progress photos so you can see the work even if you can’t be on-site. We close with the 365-Day Done Right Promise in writing: if anything isn’t right within a year, we make it right.
How Much Does Room Addition Contractor Cost in San Antonio?
A typical room addition in San Antonio runs $180 to $340 per square foot for site-built work, so a 300-square-foot bedroom addition lands roughly between $54,000 and $102,000 before finishes when you hire a Room Addition Contractor in Universal City like Benson ADU San Antonio. A modular or prefab addition from a brand like Plant Prefab or Boxabl runs lower, usually $120 to $220 per square foot. A sunroom sits in the middle at $150 to $280 per square foot. An ADU conversion of an existing garage can run $120 to $250 per square foot because the shell already exists.
What affects the price:
- Foundation type: slab-on-grade is standard, but pier-and-beam or a raised foundation adds cost on sloped lots.
- Site access: tight lots in neighborhoods like Terrell Hills or Alamo Heights can add crane or material-handling time on modular sets.
- Finish level: builder-grade trim versus custom millwork swings the final number by 20% or more.
- Existing conditions: knob-and-tube wiring, a maxed electrical panel, or an aging roof intersection all add line items.
- Brand choice: Boxabl and Plant Prefab have different cost structures than site-built framing, and we show you both options side by side.
How to avoid overpaying: Get a written, line-item estimate before work starts. A verbal estimate that shifts after demo day is the most common way San Antonio homeowners end up over budget. Ask for a fixed price with a written scope of work, and ask what happens if the price moves. Our free estimate includes every line item: permits, labor, materials, and the 365-Day Done Right Promise, so there is nothing hidden in fine print. Call (430) 258-2928 and we’ll walk you through it.
Our Service Area Near San Antonio
Benson ADU San Antonio works across the San Antonio metro, including Room Addition Contractor in Schertz, Room Addition Contractor in Live Oak, Leon Valley, Alamo Heights, Windcrest, Bulverde, Converse, Kirby, Castle Hills, Lackland AFB, and Terrell Hills. Typical response for an initial site visit is within a few days depending on your neighborhood. If you’re just starting to explore, our home page covers the full range of ADU and addition work we do across the region. And if you want to see how we approach the work closer to the city center, see Room Addition Contractor in San Antonio for more detail.
Serving San Antonio, TX - Our Local Coverage Area
We’re based in the San Antonio area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked Questions About Room Addition Contractor in San Antonio
A Room Addition Contractor in Schertz is a licensed professional who designs, permits, and builds new living space attached to your existing home. That includes foundations, framing, roofing, electrical, plumbing, drywall, and finish work. Benson ADU San Antonio handles the full scope, from the first measurement to the final inspection, with a written price before work starts.
Most single-room additions take 8 to 16 weeks from permit approval to final walkthrough, depending on scope and finishes. Prefab and modular additions from brands like Plant Prefab can trim several weeks off the framing phase. We give you a written timeline with the estimate, and we keep it updated with photo documentation as the work progresses. Call (430) 258-2928 for a more specific timeline based on your project.
Site-built room additions in San Antonio run $180 to $340 per square foot, while modular and prefab additions run $120 to $220 per square foot. A 300-square-foot addition therefore lands between roughly $36,000 and $102,000 depending on the build method and finishes. Your written estimate from Benson ADU San Antonio will show every line item, so you can compare apples to apples.
Yes, we are authorized to build with Boxabl and Plant Prefab systems, and we regularly use James Hardie cladding on both prefab and site-built work. We’ll show you pricing for multiple brand options so you can choose based on cost, timeline, and finish. If you already own a unit or have a brand preference, call us for a site assessment.
If an addition or conversion you already have is causing structural strain, leaking, or otherwise creating a safety issue, a live person answers our phone 24/7. We prioritize urgent assessments, and we’ll tell you honestly if the problem can wait for a scheduled visit or needs immediate attention. Your safety and the structural integrity of your home come first.
Every Benson ADU San Antonio project includes the 365-Day Done Right Promise: if any covered work isn’t right within a full year, we make it right at no charge. That’s a written guarantee stamped on every project, and it includes a free second visit if any covered repair fails. We put that promise in the contract before any work starts.
Start by listing what you need the space to do: who will use it, what furniture or fixtures go in it, and what budget range you can commit to. Then call us at (430) 258-2928 for a free site assessment. We’ll handle the measurements, the permit research, and the written estimate, so the hard part is done for you.
Schedule Your Room Addition Service in San Antonio Today
If you’re ready to stop guessing and start pricing, call Benson ADU San Antonio at (430) 258-2928 today. Troy Eastman and our team will give you a free written estimate, walk you through brand options like Boxabl and Plant Prefab, and answer every question with real numbers. No obligation, no pressure, and no price that changes at the door.
Written by Troy Eastman, Owner at Benson ADU San Antonio, serving San Antonio since 2006.
