How Much Does It Cost to Build a Duplex?

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Written By Justin McGill

DealBloom aims to share the latest tips and strategies to help realtors, brokers, loan officers, and investors navigate the world of real estate.

If you want to try a real estate developer career path, you probably want to know how much does it cost to build a duplex. In addition to creating equity, a duplex also increases rental returns. This makes them an attractive investment for those looking to make money in the real estate market.

A duplex investment is a great way to create equity and increase rental returns.

I remember when I was first considering building a duplex, I did some research and found that the average cost to build a duplex is between $150,000 and $300,000. Of course, many factors can affect the final cost, but this gives you an idea of what to expect.

How Much Does It Cost to Build a Duplex?

The final number on how much does it cost to build a duplex will ultimately depend on the size of the duplex, the materials used, the location, and the contractor you choose.

Like other types of apartments, duplex homes are built using similar materials and styles. However, their cost varies depending on the location.

Building side-by-side apartments is more expensive than building single-family homes. The cost of building a duplex is around $95 to $220 per square foot.

Most duplex owners spend about $130 per square foot on renovations.

Types of Duplexes

You can build a duplex in two ways: horizontal or vertical. One unit is on top of the other in a two-story building, or two units are side by side.

Both units are the same shape, size, and layout and each has an entrance.

The cost of building a side-by-side duplex is usually more expensive regardless of whether it is single or two-story.

This is because most duplex homes have two units that sit side by side, which often results in additional expenses for the roof, frame, and plumbing services. These extra costs can be mitigated by stacking apartments on top of each other.

The price range for duplexes is between $95 and $135 a square foot. While a side-by-side duplex can have two separate apartments, a stack style with only one unit above the other is the cheapest to build.

By putting two apartments on top of each other, you reduce the amount of space you need to cover with roofing materials and concrete. You also make it easier and less expensive to run plumbing and electrical lines.

One-story duplexes typically cost between $110 and $180 per square foot. These homes are two units, side by side, each on only one level.

This means that a two-story duplex requires more space and a larger roof and foundation than a one-up, one-down duplex. Even if the apartments in both types are identical in floor plans, the two-story duplex is more expensive to build.

A side-by-side duplex costs anywhere from $130 to $220 per square foot. This is the most commonly built type of duplexes.

In this style of apartment, there are two floors, which are mirror images of each other. They are larger than other styles, have more square feet, and are more expensive.

They have the disadvantages of a one-story such as having a larger roof and foundation and a decentralized plumbing system, while they also incur additional costs for adding a second level.

Estimated Costs to Build a Duplex

According to some estimates, the average cost of building a house is roughly $150 to $200 per square foot.

This means you would spend between $225,000 and $300,000 for a home with a 1,500-square-foot living area.

The cost of building a duplex depends on the size, location, and current housing market.

The average cost of a single-family home in the U.S. is $138,500, with 900 square feet of living space and a 30 x 60-foot floor plan.

This equates to $154 per square foot for materials of average quality.

This price includes all materials, labor, and finishing touches, including windows, doors, a poured concrete base, a finished basement, and all major appliances and fixtures.

Land and building costs are not included in the cost of building a duplex. You still need to pay for the lot, which can be expensive if the property is not already a single-family home.

Labor Costs

Each property is unique and will have different costs. Your specific labor, material, and time requirements will vary.

For an idea of how much this project will cost, you can break down all of the different components. Some prices may change depending on where you live.

The architect, engineer, and contractors’ fees are added to the total cost of your project instead of being included in the original price.

The Modular Duplex

Stick-built houses, which are typically constructed on-site, are inefficient and take a long time to build. A modular house, on the other hand, is much faster and can be built in segments off-site.

The modular building process involves transporting finished pieces to a job site for assembly. This usually requires more materials and stricter building allowances, as the house must be able to withstand transport.

However, the use of computer-aided programs and technology can help speed up the build process and reduce costs.

Modular duplexes offer a more affordable option for those looking to invest in a duplex property. On average, modular duplexes cost $100 per square foot, while the average stick-built duplex costs $150 per square foot.

This makes modular duplexes a more budget-friendly choice for those interested in this type of investment.

How Much Land Do You Need?

The amount of land needed for a duplex can vary. Stacked duplex homes use vertical space to create additional rooms, which generally makes them require less land area than side-by-side or single-stories.

Generally, the lot should be between 2.5 to 3.5 times that of the square footage of a private home.

Because apartment buildings are shared by many people, you may decide that you don’t need much space around the entire complex, or you may need more yard space for each unit.

Both cases are acceptable as long as your apartment building complies with your local building codes.

How to Convert a Single Family Home to a Duplex

If you’re considering converting a single-family home into a multi-family property, there are many benefits, such as having an extra room to rent out or housing a friend or family member.

Not all homes are eligible for duplex conversion, though. Some are not set up in a way where it makes sense – a duplex has two separate living spaces, and some houses cannot easily be converted.

Some homes are not zoned for multi-family buildings and cannot be legally converted.

You’ll need to put in new windows and doors, and insulate the walls. You’ll also need to install a second kitchen and bathroom. All of this will cost an estimated $80,000 to $100,000.

Pros and Cons of Living in a Duplex

Living in a duplex has both pros and cons. On the plus side, if you own the rental unit, you can collect rent to help pay off your mortgage. On the negative side, you have to deal with renters, which can be stressful.

Living with your tenants means that you’re always there for them, whether for maintenance or a complaint.

If both you and the other tenant are renting, this could mean having to interact with them regularly.

If the other renter is a friend or family member, this may be beneficial. But this can be problematic if it’s someone who you don’t get along with.

Duplexes have some shared areas, like the roof and foundation. This means that if something needs to be repaired, it could impact both residences at once.

If it’s not your side, you still have to deal with it at some level.

One of the benefits of living in a duplex is that you typically only have one other family to deal with, as opposed to several. This can often create a more relaxed living atmosphere.

What is the Average Size of a Duplex?

According to the National Association of Home Builders, the average size of a duplex unit is 1,500 square feet. This figure will vary depending on the location and type of duplex.

Is a Duplex Worth Buying?

A duplex is two homes in one, so it can be a great investment. The income from renting out one side can help to cover the mortgage and other expenses, and you may even be able to live in the other unit for free.

Duplexes can also appreciate over time, so they can be a good long-term investment.


How much does it cost to build a duplex? The average cost to build a duplex is between $150,000 and $300,000. Of course, many factors can affect the final cost, but this gives you an idea of what to expect. If you’re thinking about building a duplex, be sure to factor in all of the costs involved before making your decision.

Justin McGill