Back to Blog Casita / ADU How Much Does It Cost to Build a Casita in San Antonio? (2026 Pricing Guide)
Mark WhiteJune 17, 20268 min read What Does a Casita Actually Cost to Build in San Antonio?
If you're considering building a casita (also called an ADU, guest house, or in-law suite) on your San Antonio property, the first question is always about cost. The short answer: casita construction in San Antonio typically ranges from $100 to $250 per square foot, depending on size, finishes, and site conditions.
But the real answer is more nuanced, and there are significant City of San Antonio incentives that can dramatically lower your out-of-pocket costs. As one of the contractors on the City's official Casita Contractor List, Legacy Home Improvements builds casitas across Greater San Antonio and helps homeowners navigate the incentive process.
Casita Cost Breakdown by Size
San Antonio allows casitas up to 800 square feet (or 50% of your primary home's living area, whichever is less). Here's what typical projects cost before incentives:
- Small casita (375-400 sq ft, 1 bed/1 bath): $40,000 to $100,000. These are ideal for a single family member or rental unit.
- Medium casita (500-600 sq ft, 1-2 bed/1 bath): $60,000 to $150,000. The most popular size for rental income or family use.
- Large casita (700-800 sq ft, 2 bed/1 bath): $80,000 to $200,000. Maximum space for a comfortable two-bedroom layout.
- Design fees: $0 to $4,500+. Using a City-approved permit-ready plan (starting at $450) eliminates custom architecture costs.
San Antonio City Incentives: Up to $35,000 in Forgivable Loans
The City of San Antonio's Casita Incentives Pilot Program is a game-changer for homeowners. These are forgivable loans, meaning you never pay them back as long as you meet the program requirements.
Level I offers up to $25,000 as a 5-year forgivable loan for homeowners earning up to 80% of the Area Median Income. Level II offers up to $35,000 as a 10-year forgivable loan for homeowners earning up to 50% AMI. On top of that, the City may reimburse up to $4,500 in design fees and waive City permit fees and SAWS connection fees.
That means a $100,000 casita project could effectively cost as little as $60,000 to $70,000 after incentives and fee waivers. Legacy helps you apply for and maximize these benefits as part of our service.
What Factors Affect Casita Construction Costs?
Every casita project is different. Here are the main factors that influence your final cost in San Antonio:
- Lot conditions: Slope, soil type, tree removal, and utility access all affect foundation and site prep costs.
- Plan type: Permit-ready City plans are the most affordable starting point. Custom designs add architectural fees but allow maximum flexibility.
- Finishes and materials: Standard fixtures keep costs lower. Upgraded countertops, flooring, and appliances increase the budget.
- Utility connections: Running water, sewer, and electrical to a detached casita can add $5,000 to $15,000 depending on distance from the main house.
- Foundation type: Slab-on-grade is most common and affordable. Pier-and-beam costs more but works better on certain lots.
- HOA requirements: Some HOAs have additional design or material requirements that can affect cost.
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The City of San Antonio offers five architect-designed, permit-ready casita plans ranging from 375 to 800 square feet. These plans are pre-approved by the City, which means faster permitting and no custom design fees. Legacy offers all five plans and can walk you through which one fits your lot and lifestyle.
Using a permit-ready plan can save $5,000 to $15,000 in architectural fees alone, plus weeks of design time. And if you qualify for City incentives, the design fee reimbursement can cover the plan purchase cost entirely.
How to Finance Your San Antonio Casita
Beyond City incentives, San Antonio homeowners have several roof financing options for casita construction:
Home equity loans and HELOCs use your existing home equity to fund the build at competitive rates. Construction loans are designed specifically for building projects and convert to a mortgage upon completion. Cash-out refinancing may work if you have significant equity and want to consolidate. Personal loans can work for smaller projects but typically carry higher rates.
Legacy Home Improvements can help you understand your options and connect you with local lenders experienced in casita financing.
Ready to Get a Casita Cost Estimate?
Every property is different, and the best way to get an accurate instant roof estimate for your San Antonio casita is a free consultation with Legacy Home Improvements. We'll assess your lot, review your goals, check incentive eligibility, and provide a detailed cost breakdown. As an official City of San Antonio casita contractor with over 25 years of local building experience, we make the process simple from start to finish.
Call us at (210) 272-7272 or visit our Casita Program page to get started.
Have Questions? Call Us Directly
Talk to a real person, not a call center. Mark and the Legacy team answer roofing questions all day, every day.
Call (210) 272-7272 → MW Mark White
Owner, Legacy Home Improvements · San Antonio since 1999
Mark has been in the roofing business for over 25 years. He personally inspects homes, works with insurance adjusters, and answers every email at mwhite@legacytx.com.
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