How much does it cost to build a duplex?
$150 – $280 cost per square foot
$300,000 – $560,000 total average cost
Average cost to build a duplex
The average cost to build a duplex is $150 to $280 per square foot or $300,000 to $580,000 for 2,000 total square feet. The final cost to build a duplex home depends on the location, size, material quality, and structure type. Side-by-side duplexes are the most common type but cost more than unit-over-unit duplexes.
|National Average Cost||$430,000|
|Average Range||$300,000 to $580,000*|
*Not including the cost of the land
What is a duplex home?
A duplex is a multi-family home that connects two individual residences under one roof, separated by a partition wall or ceiling. Duplexes have separate entrances, interiors, and garages. This allows landlords to charge rent from two households, making it more profitable than a single-family residence.
Cost to build a duplex by size
The following table shows the average cost to build a duplex depending on its square footage:
|Total square footage||Average total cost*|
|1,000||$150,000 – $280,000|
|2,000||$300,000 – $560,000|
|3,000||$450,000 – $840,000|
|4,000||$600,000 – $1,120,000|
|5,000||$750,000 – $1,400,000|
*Not including the cost of the land
Cost to build a duplex by type
Most duplexes are side-by-side and separated by a vertical wall. Sometimes developers stack the units on top of each other, separating them by a ceiling or floor.
|Type||Average cost per square foot*|
|Unit-over-unit||$150 – $190|
|Side-by-side||$160 – $280|
*Not including the cost of the land
Unit-over-unit duplexes cost $150 to $190 per square foot and are cheaper to build than side-by-side duplexes because they require a smaller foundation and roof. Contractors can also save money by centralizing piping and wiring. The only downside to this duplex type is that second-level units are more difficult to access than ground-floor units.
Side-by side duplex
Side-by-side duplexes cost $160 to $280 per square foot, depending on the number of stories, and typically have a bigger footprint than unit-over-unit duplexes. Single-story side-by-side duplexes cost $160 to $220 per square foot, while two-story side-by-side duplexes cost $180 to $280 per square foot.
Duplex building cost factors
Building a duplex includes many projects that require several different professionals. Each task varies in cost and depends on the quality of materials, local labor rates, and duplex size.
|Factor||Average cost per square foot|
|Foundation cost||$5.00 – $33.00|
|Framing cost||$11.00 – $30.00|
|Drywall cost||$1.50 – $3.50|
|Flooring cost||$4.00 – $15.00|
|Plumbing cost||$4.00 – $5.00|
|Interior trim cost||$4.00 – $10.00|
|Siding cost||$4.00 – $13.00|
|Roof cost||$3.00 – $6.00|
|Insulation cost||$1.00 – $4.50|
|Electrical wiring cost||$4.00 – $9.00|
|HVAC system cost||$3.00 – $6.00|
|Interior painting cost||$1.00 – $3.00|
|Countertops cost||$50.00 – $150.00|
|Driveway cost||$3.00 – $12.00|
|Garage cost||$35.00 – $60.00|
|Doors cost||$225 – $1,900 each|
|Windows cost||$450 – $1,500 each|
|Light fixtures cost||$70 – $300 each|
|Toilets cost||$350 – $800 each|
|Sinks cost||$330 – $1,300 each|
|Cabinets cost||$150 – $500 per linear foot|
|Appliances cost||$2,500 – $6,800 per kitchen|
The following factors also affect the cost of building a duplex:
Duplex design – Basic fixtures cost less than luxury materials. Luxury homes cost more to build but tend to make more money in rent.
Region – Duplexes built on the east or west coast typically cost more than in the Midwest or south. Homes that are close to restaurants, schools, major cities, and bodies of water are also worth more.
Land – Before you can build a duplex, you’ll need to purchase the land. Lots cost $3,000 to $150,000, depending on the size and location.
Hard vs. soft costs – Hard costs include the materials, labor, utilities, and other costs that directly relate to construction. Soft costs include designing, inspections, permits, taxes, and other indirect costs.
Financing – The cost of borrowing money from a bank, lender, or investor includes processing fees and interest.
Maintenance – After construction, you may need to pay ongoing fees for utilities, landscaping, and other relevant maintenance.
Building permits – General contractors normally obtain building permits and include them in their labor fee. Research zoning regulations for multi-family homes before buying land to confirm you can build a duplex in your desired location.
Before you can build a duplex, you’ll have to hire several different professionals to help design the building, make sure the land and plans are sound, and begin construction:
An architect charges $100 to $250 per hour.
A structural engineer charges $100 to $220 per hour.
A general contractor costs $50 to $150 per hour.
Electrician services cost $50 to $130 per hour.
Plumber services cost $45 to $150 per hour.
An interior designer costs $50 to $200 per hour.
If you haven’t bought a lot to build your duplex on yet, consider hiring a real estate attorney to assist with construction laws, zoning regulations, and drafting contracts for builders.
Converting a single-family home into a duplex
Converting a single-family home into a duplex costs $50,000 to $100,000 on average. Some people consider this project when having family members live with them or in order to bring in rental income. However, there are cases when this conversion is not possible.
Check local zoning laws to make sure the property is eligible to be turned into a multi-family dwelling. Next, consider whether you could reasonably cut the floor plan in half vertically or horizontally. You may need to reroute plumbing or electricity, construct walls, and add new exterior doors.
Duplex building FAQs
Is building a duplex worth it?
Building a duplex is worth it if you value the potential for flexible rental income. You can rent out both units in a duplex or live in one unit and rent out the other. However, being a landlord comes with extra responsibilities like collecting rent and maintaining the property.
How long does it take to build a duplex?
Building a duplex takes about 12 months, depending on its size and number of stories. Delays from materials shortages, disputes, or inclement weather can draw out the process.
Is it cheaper to buy or build a duplex?
Buying a duplex is typically cheaper than building a new one. The final cost depends on the condition of the existing property, the location, and the quality of the building materials.
How big of a down payment do you need to build a duplex?
Building a duplex requires a 10% to 20% down payment, depending on your credit score and local rates. Sometimes, you can take out a home equity line of credit (HELOC) on an existing property to finance the project.
Getting estimates from duplex construction companies
Choose builders with the best reviews on HomeGuide and Google.
Ask to see a portfolio or pictures of past projects.
Get a few different estimates to compare.
Choose contractors that are licensed, bonded, and experienced.
Get a written estimate and contract before making payments.
Questions to ask duplex builders
When hiring builders, remember to ask these questions:
How long have you been in business?
Can you give me any references from past clients?
Will you hire subcontractors, plumbers, and electricians?
How much input can I provide during the building process?
What are your labor rates currently?
Can you get me any discounts on materials?
What delays or extra fees can I expect, if any?
Can you give me a written estimate and contract?