Building Up? Here’s the Cost to Add a Second Story to Your Home

You’ve decluttered, reorganized, and maybe even rearranged some furniture, but there’s no getting around the fact that you’ve outgrown your single-story home. Maybe your family has expanded, or perhaps you’re now working permanently from home. Whatever the situation, you need more space — and you’d rather not go through the hassle or sacrifice of selling a house you otherwise love. Instead, you’re seriously considering the alternative of building up.

To put together this cost guide for homeowners like you, we combined reputable pricing information from our online research with insights from contractors and builders who have spearheaded these types of massive projects in the past.

Before we dive in, be warned: This decision is drastic and probably a lot more expensive and disruptive than you realize. Take the time to digest all of the information, crunch the numbers, and go in eyes-open to determine whether building up is really better than moving on.

Get a Home Value Estimate Before You Renovate

Home values have skyrocketed over the past two years. As you plan whether to sell or build up, start with a preliminary estimate of how much your home is currently worth.

National averages for second-story additions

Justin Bride, principal at Ascent Contracting in Denver, Colorado, has worked with many residential expansions. Over the past 18 months, he’s seen some pretty significant pricing increases for this type of project. “In Denver, we’re not sure if those increases are mostly attributed to continued effects from the pandemic and the ensuing supply chain constraints, or whether they are the result of continued increased demand,” he says.

Prices for this project will vary across states and markets, but below are some general averages for adding a second story in the U.S.

Source: HomeAdvisor

Average cost per square foot: $100-$300

Low and high-end cost range: You’ll pay somewhere between $80,000 and $600,000.

Methodology: HomeAdvisor collects a short cost survey from homeowners who use their site to find renovation professionals.

Source: Fixr

Average cost per square foot: $100-$300

Low and high-end cost range: Expect to pay $100,000-$300,000 for a home 1,000 square feet or larger. Owners of small homes (~600 square feet) may complete the project for $60,000-$180,000.

Methodology: Fixr pulls its cost data from multiple sources, including “specialized publications, websites, cost studies, U.S. associations, reports from the U.S. government, contractors and subcontractors, material suppliers, material price services, and other vendor websites.”

Source: HomeGuide

Average cost per square foot: $100-$300

Low and high-end cost range: Depending on the size of the space and quality of the materials, HomeGuide estimates a price range of $100,000-$350,000 for this project.

Methodology: HomeGuide receives millions of requests for home improvement cost estimates every year. The site then tracks cost estimates consumers get from local companies and shares pricing information.

Types of second-story additions

Not all second-story additions have the same scope. Depending on how much space you need and the size of your budget, you can choose from the following options:

Full-story addition

If you need a lot of extra space, you can opt to add a full second story that’s roughly the same size as the first story. In the below example, a full second story was added to this Denver, Colorado home:

Source: (Ascent Contracting)
Source: (Ascent Contracting)

Partial addition

If you only need to add a small amount of extra space — perhaps an extra bedroom and bathroom — and are working on a smaller budget, adding a partial second-story addition might be the way to go.

Architect Jeff Pelletier points out in a blog post that whether you add just one primary suite or three additional bedrooms and a bathroom, many of the associated costs (not to mention the disruption to your day-to-day life) will be largely the same. “I usually advocate to aim for the three-bed/two-bath second floor,” he recommends. “It is a solid investment as it is so desirable, and helps ensure the value of your investment.”

Below is an example of a partial second-story addition in California:

Source: (Design Everest)
Source: (Design Everest)

Bonus room addition

Another way to increase your living or storage space without expanding your house’s footprint is to add a bonus room over the garage. It could be used as a home office, in-law suite, man cave, playroom, craft room, storage room…the possibilities are endless. One of the main benefits of going this route is that because you’re building on top of an unfinished garage, you don’t have to worry as much about damaging existing drywall, flooring, or other elements during construction, which means there will be less need to remodel the space after the addition is complete.

Not all garages are candidates for supporting bonus rooms without significant structural rework to the existing foundation, particularly in the case of detached garages. “Sometimes it makes more sense to demolish the existing garage if the goal is to build a new garage with an ‘accessory dwelling unit’ (or ADU) on top,” says Bride, the Colorado contractor.

Estimated cost to add a second story in 4 cities

Just as home prices vary widely from one market to the next, the cost of a home addition can range dramatically based on where you live. We spoke with some experienced contractors in four different cities to get an idea of the price variances for home additions across the U.S.

Los Angeles, California

Full second story cost: $550,000-$1,000,000, depending on interior and exterior finishes

Partial second story cost: $165,000-$300,000, depending on interior and exterior finishes

Garage bonus room cost: $150,000-$175,000

According to: Oren Farkash, general contractor for South Land Remodeling in Los Angeles, California, and winner of “Best of Houzz” for four consecutive years

Denver, Colorado

Full second story cost: $350,000-$550,000, depending on interior and exterior finishes

Partial second story cost: Approximately $250,000

Garage bonus room cost: Approximately $82,500

According to: Justin Bride of Ascent Contracting, which specializes in residential renovations and additions

Houston, Texas

Full second story cost: $360,000-$500,000 (for a 2,000-square-foot house)

Partial second story cost: $90,000-$125,000 (for 500 square feet)

According to: Legal Eagle Contractors, a Houston-based construction firm that has completed many second-story additions

Seattle, Washington

Full second story cost: Approximately $400,000-$550,000

Partial second story cost: Approximately $250,000-$300,000

Garage bonus room cost: Approximately $150,000

According to: Architect Jeff Pelletier, writing for Board & Vellum

Is it cheaper to build up or out?

Every home and every project is different, but Bride says that overall, it’s less expensive to build out onto your lot space than it is to build up. When you build out, there’s no need to reinforce the existing foundation. In addition, when you add onto the back or the side of an existing house, you’ll need to remodel the breached wall. But when you add a second story, you remove the roof and will possibly need to remodel several walls and rooms.

That said, when you build out, you sacrifice the existing square footage of your lot. If you don’t have enough physical space to increase the footprint of your house or don’t want to infringe on your yard space, it may be worth the extra investment to expand vertically.

Additionally, building up could dramatically increase a home’s curb appeal and boost its value for resale. According to HomeAdvisor, homeowners can expect roughly a 65% return on investment (ROI) for a full two-story addition.

With a second-story addition, you’ll also save money on digging and excavation, which can cost $1,519 to $5,935, as well as on pouring a new foundation, which can run you anywhere from $4,032 to $14,340 or $5 to $37 per square foot, according to HomeAdvisor.

As a bonus, you’ll end up with a brand-new roof, which has been shown to provide up to a 94% return on investment.

What makes second-story additions so expensive?

Now that you have some estimates for this project, you may be wondering where all of those dollars are going. What are some of the most expensive components of a second-story addition?

Modifying the first floor

The contractors we spoke with agree that the need to reconfigure or remodel the first floor to accommodate the second-story addition ratchets up the total project cost. In many cases, the existing walls need to be reinforced to support the weight of the new ceiling. Bride often ends up replacing the first-floor windows, doors, and trim to match the new second story.

Plumbing/electrical/HVAC systems

When adding a second story, these systems will have to be moved, expanded, or upgraded to accommodate the extra square footage, which can be a complex and expensive task. Electrical wiring and plumbing may also have to be altered to meet the new code.

Exterior construction

With some additions, Bride has also added exterior decks, rooftop decks, or wrap-around porches, which can add a significant expense. The project can also involve reconfiguring exterior landscaping, fencing, and other site work.

Foundation work

If the existing foundation needs to be reinforced to support the new level, it can add extensive time, cost, and challenges to the overall project — but it’s necessary to ensure safety and stability.

Smart ways to make an addition less of a budget-buster

There’s no way around it — you’ll have to pony up a big chunk of change to add a second story. But there are some ways to soften the blow to your bank account:

  • Farkash, the contractor in Los Angeles, recommends choosing standard finishes instead of high-end options to save significantly on cost.
  • When possible, be flexible with the design. If your designer or contractor suggests an alternate layout that’s more cost-effective, consider taking his or her advice.
  • The simpler the design of your addition, the less it will cost. More complicated layouts will always be more expensive.
  • Be open to tackling some project elements yourself. If you’re the DIY type, you might want to take on the demolition work or painting instead of paying someone else to do it. Another option would be to order products yourself from less expensive sources.

Common headaches associated with second-story additions

Rarely does a home improvement project go smoothly from start to finish, particularly with something as major as adding a second story. To help minimize expensive setbacks and unwelcome surprises, be prepared for the common challenges associated with building up.

Supply chain issues

In Denver, Bride has seen a marked decrease in the availability of most materials, as well as increased lead times on finished products such as cabinets, windows, exterior doors, and appliances. “It seems that most finished products that get made up from various types of raw materials or separately manufactured parts are in the shortest supply and have the most vulnerability to supply chain issues,” he says.

Lack of transparency from the builder

Bride cites this as the most common problem encountered with residential construction projects. When the builder isn’t honest with the homeowner or there is a lack of communication, it can result in the homeowner’s expectations not matching what is delivered. “It’s important to contract with a reputable firm that emphasizes open and clear communication, refined project management and delivery methods, and transparency in project cost, both during pre-construction and construction,” says Bride. To combat this problem, he suggests choosing the building and design teams early, so the builders can act proactively during the preconstruction phase and have ample time to purchase the necessary materials.

Weight-bearing issues

Not every single-story home has a strong enough foundation to support another floor. Before you start building up, you’ll need to hire a structural engineer to inspect the existing house to determine whether it’s strong enough to hold the extra weight. If not, the slab, walls, beams, and other supporting elements will need to be fortified or replaced, which can drive up the cost of the project even further. To find a structural engineer, start by calling a local architectural firm or your local building code/inspection office for recommendations.

Adding a staircase

A second story is only useful if it can be accessed, hence the inevitable staircase. This can be a challenge if the existing layout of the first floor doesn’t have enough open floor space to accommodate a staircase. Some homeowners opt to place the staircase outside the home to conserve floor space and save money.


While the roof is removed, there is always some degree of risk that rain or snow could compromise the interior of the home, although your contractor should have the area covered with tarps to help keep moisture out.

Renovating? Check your home value first

How much is your home worth today? In as little as two minutes, HomeLight can provide you with a preliminary estimate of value in preparation of your plans to renovate, remodel, or make repairs.

Build up or buy: Is it worth it to add a second story?

When trying to decide whether this renovation is worth the time, expense, and hassle, you’ll want to weigh these five important factors:

  1. Attachment to your current home: If you have a strong sentimental attachment to your house, as well as strong bonds with your neighbors and community, it may be tougher for you to make the sacrifice to sell.
  2. Affinity for construction: Undergoing a major renovation is not for the faint of heart. If you’ve already tackled some big projects, you enjoy the remodeling process, and you’re not afraid of the inevitable hassles along the way, you may be better equipped to execute this project.
  3. Availability of time and costs: Adding a second story is not a quick or cheap endeavor. Consider whether you can spare the weeks (or months), the significant expense, and whether the payoff will be worth it.
  4. Cost of the project vs. price of a different home: To determine whether it makes financial sense to build up, you’ll need to compare the projected costs to the market price of a similar home in your area. Plug your address into HomeLight’s Home Value Estimator to get a preliminary home value estimate in less than two minutes.
  5. Your patience level: Bride says that if you’re just starting to think about whether you want to take on this project, you should expect to wait at least a year before being able to build — but don’t consider that a complete waste of time. In fact, he sees it as the most important phase of the project. “That year-long waiting period, which we call the project development phase, is when families have the most ability to affect the outcome of the project in terms of finish level, price, and smooth construction,” he explains. “It’s definitely in everyone’s best interest during this time to work energetically so that designs can be finalized, interior finishes can be selected, and materials can be purchased well in advance so that projects are not held up during construction.”

If the price of the addition is within your budget and is less than the market price of typical two-story homes in your area — and if you have at least several months to spare, plenty of patience, and the inclination to tackle a project of this scale — building up can be a creative and practical way to get the space you need. However, if the project costs are higher than purchasing a new home, or if you’re time-crunched and need more square footage immediately, it may make more sense to sell and purchase a new, bigger home.

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Header Image Source: (Roger Starnes Sr / Unsplash)