Use this guide to budget for building a saltbox house based on factors such as location, size, labor, and finishing costs.
How Much Does It Cost to Build a Duplex in 2025?
Normal Range: $293,000 - $549,000
Building a duplex costs $402,000 on average
How we get this data
Javier Ballester / ADDICTIVE STOCK / Adobe Stock
Javier Ballester / ADDICTIVE STOCK / Adobe Stock
Highlights
Qualifying for duplex construction can affect financing, zoning, and permits.
Average costs range from $293,000 to $549,000.
Size, location, materials, and labor rates have the biggest impact on your budget.
A duplex can generate rental income or create a flexible multigenerational living space.
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This article was updated using automation technology and thoroughly reviewed for accuracy by HomeAdvisor Editor Ryan Noonan.
The cost to build a duplex falls between $293,000 and $549,000, with most homeowners spending an average of $402,000. Prices rise or fall with square footage, local labor rates, material quality, and the overall design. Smaller duplexes can go as low as $128,000, while larger duplexes or more complex construction projects can run as high as $1,120,000.
How Much Does It Cost to Build a Duplex?
Construction is the largest expense in any duplex project, and it’s made up of dozens of moving parts. From laying the foundation to installing the final coat of paint, every stage adds to your total cost. The materials you choose, local labor rates, and the overall design will all influence how much you spend per square foot. The tables below outline the costs you can expect to incur when building a duplex.
Building a Duplex Construction Prices
Construction costs for a duplex can vary widely depending on the materials, labor rates, and complexity of the build. Here’s a breakdown of estimated per-square-foot prices for each major component of the build.
| Building Component | Estimated Cost per Sq. Ft. |
|---|---|
| Concrete slab or foundation | $5–$33 |
| Lumber and framing labor | $11–$30 |
| Roof structure and materials | $3–$6 |
| Flooring (material + install) | $4–$15 |
| Exterior finish (siding) | $4–$13 |
| Drywall installation & finish | $1.50–$3.50 |
| Interior paint application | $1–$3 |
| Heating and cooling (HVAC) | $3–$6 |
| Electrical system setup | $4–$9 |
| Plumbing rough-in and fixtures | $4–$5 |
Building a Duplex Labor Prices
Bringing a duplex to life takes more than just materials and labor—it requires a skilled team of professionals. From design to final inspection, each expert plays a crucial role in ensuring your build is safe, efficient, and compliant with all relevant codes.
| Professional | Role & Responsibilites | Fee or Rate |
|---|---|---|
| General Contractor | Manages the entire project, hires subcontractors, sources materials, and oversees quality | 10%–20% of total cost or flat fee (e.g. $50–$100K on a $500K build) |
| Architect | Designs plans, ensures code compliance, prepares permits, and may oversee construction | $100–$250/hour, flat fee, or 10%–15% of project cost |
| Interior Designer | Plans layouts, selects finishes, and ensures functional interior design | $50–$200/hour based on scope |
| Structural Engineer | Designs foundations, analyzes loads, and handles inspections for safety and compliance | $100–$220/hour |
| Electrician | Installs wiring, panels, and lighting and ensures code compliance | $50–$130/hour |
| Plumber | Installs pipes, fixtures, and ensures water and waste systems are to code | $45–$150/hour |
Cost to Build a Duplex by Size
Building a duplex is a complex project that involves numerous components and various professions. The cost to build a duplex varies from $115 to $240 per square foot, including parts and labor.
| Duplex Size (Sq . Ft.) | Cost Range |
|---|---|
| 1,500 | $172,500–$360,000 |
| 2,000 | $230,000–$480,000 |
| 3,000 | $345,000–$720,000 |
| 4,000 | $380,000 – $880,000 |
| 5,000 | $475,000 – $1,100,000 |
Additional Expenses
Beyond materials and labor, a range of secondary costs can affect your total duplex budget. These include permits, site prep, insurance, and post-build services—expenses that can sneak up if you’re not prepared.
Demolition and Site Prep
If there’s an old structure on your lot, demolition will come first. Clearing the site can cost anywhere from $3,000 to $25,000, depending on size, location, and ease of access. Lots with slopes, trees, or tight access points may require extra work. Don’t forget to factor in debris removal and disposal fees.
Permitting
Duplex builds require permits for construction, zoning, utilities, and sometimes environmental review. These fees vary by location and project scope, and the application process can take weeks or even months. Your contractor may handle permitting, but in some areas, homeowners are required to do it themselves, so be sure to check.
Other Expenses
Taxes, insurance, warranties, and optional upgrades—such as smart technology or accessibility features—can increase your budget. Once construction is complete, plan for move-in costs, including repairs, inspections, and a professional cleanup.
Ways to Keep Duplex Construction Costs Down
Thoughtful planning and a few strategic choices can help you stay on budget during your duplex build:
Opt for ready-made building plans instead of commissioning a fully custom design.
Purchase materials from local suppliers to reduce freight and delivery costs.
Get multiple quotes from contractors and design pros to ensure you're paying fair market rates.
Start your project in the off-season when construction demand—and prices—may be lower.
Stick to standard finishes and avoid splurging on premium appliances unless necessary.
Install energy-efficient systems that can save you money over time on utility bills.
If your budget is tight, consider breaking the project into phases.
Utilize reclaimed or surplus materials whenever possible to minimize waste and reduce costs.
Take on simple DIY projects, such as painting or landscaping, to reduce labor expenses.
DIY vs. Hiring a Duplex Building Pro
Building a duplex without a general contractor may seem like a cost-saver, but it often leads to delays, code issues, and costly mistakes. While complete DIY construction isn’t practical due to the need for licensed trades, handy homeowners can cut costs by handling interior tasks like flooring, painting, and trim. For most people, hiring a local general contractor ensures the project runs smoothly and meets all safety and permit requirements.
How HomeAdvisor Gets Its Cost Data
No place is more important than your home, which is why HomeAdvisor connects homeowners with local pros to transform their houses into homes they love. To help homeowners prepare for their next project, HomeAdvisor provides readers with accurate cost data and follows strict editorial guidelines. After a project is complete, we survey real customers about the costs to develop the pricing data you see, so you can make the best decisions for you and your home. We pair this data with research from reputable sources, including the U.S. Bureau of Labor Statistics, academic journals, market studies, and interviews with industry experts—all to ensure our prices reflect real-world projects.
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