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

At HomeLight, our vision is a world where every real estate transaction is simple, certain, and satisfying. Therefore, we promote strict editorial integrity in each of our posts.

If you’re evaluating the cost to add a second story to your home, your house is likely feeling more than a little cramped. Moving for you isn’t ideal, either — it would mean giving up trail access, walkability to local shops, or a backyard sunset view. Or maybe you don’t want to leave behind a group of amazing close-knit neighbors. In any case, your location can’t beat, and you’re seriously considering the alternative of building up.

To put together this cost guide for families like you, we combined reputable pricing information from the web with insights from contractors and builders who’ve spearheaded these massive projects in the past. We’ll warn you now: This decision is drastic and probably a lot more expensive and disruptive than you realize. Go in eyes-open about what you’ve signed up for and be sure to think about whether a move would truly be worse.

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

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: For an extra 1,000 square feet, you’d pay somewhere between $100,000 and $300,000. For a complex project with high-end materials, costs can rise to as much as $500,000.
Methodology: HomeAdvisor collects a short cost survey from homeowners who use their site to find renovation professionals.

Source: Fixr
Average cost per square foot: $300-$500
Low and high end cost range: Expect to pay $150,000-$200,000 for a home 1,000 square feet or larger. Owners of small homes may complete the project for $90,000-$120,000.
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:

A house before adding a second story.
Source: (Ascent Contracting)
A house before adding a second story.
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 master 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:

A house before adding a second story.
Source: (Design Everest)
A house with a second story that was recently added.
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 Justin Bride, principal at Ascent Contracting in Denver, Colorado, who has worked with many residential expansions.

Denver, where you can add a second story to a house.
Source: (Cassie Gallegos / Unsplash)

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: $150,000-$200,000 (for a 2,000-square-foot house)
  • Partial second story cost: $90,000-$120,000 (for 500-700 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’s True Cost Guide, you can expect to recoup a 65% return on your investment when adding a two-story addition.

With a second story addition, you’ll also save money on digging and excavation, which can cost up to $4,110, and on pouring a new foundation, which can run you anywhere from $4,400 to $12,700 per 100 square feet. 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 sitework.
  • 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.
Spackle used after adding a second story.
Source: (La Miko / Pexels)

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.

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.

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.

A second story attic addition that cost money to complete.
Source: (Pixabay / Pexels)

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

The question of whether this renovation is worth the time, expense, and hassle is one that only the homeowner can answer. To gauge whether you’re a good candidate to pursue this project, Bride suggests asking yourself these important questions:

  • Do you have a strong bond with your neighborhood and neighbors? Do you love the local schools, parks, and local shops?
  • Do you love the idea of remodeling and construction? Do you enjoy seeing a project take shape in design and then watching that design come to fruition week by week and month by month?
  • Do you have the time available to design, plan, and execute the renovation, or is the extra space an immediate need?
  • Do you love the idea of contributing to the history of your home, recognizing that the changes you make will be enjoyed and valued for years to come?

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.

Header Image Source: (Roger Starnes Sr / Unsplash)