Is It Possible to Add a Basement to an Existing House?

Matt Marandola
Written by Matt Marandola
Reviewed by Robert Tschudi
Updated February 15, 2022
Modern finished basement of a home
Photo: Anatoli / Adobe Stock


  • Before breaking ground, check that your state or climate is conducive to basements first.

  • Basements are great for providing increased storage, space for entertainment, and resale value.

  • The average cost to build a full 2,000-square-foot basement with no existing crawlspace is around $110,000.

  • If you already have a crawlspace, you can add a basement for about $45,000.

  • Alternative options include a home addition or converted attic.

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Adding a basement to a house is a perfect way to create a workspace, entertainment area, or simply to have more room for a growing family. But while you can add a basement to a house, it doesn’t mean it’s always worth it.

You need to keep in mind that you’re affecting your home’s foundation, and you need to look into whether your state or climate is conducive to basements in the first place.

Benefits of Adding a Basement to a House

If adding a basement is on your wishlist, then you’re likely suffering from a storage or space problem. Building up isn’t always an option, so why not see if there’s room to build below? This is especially true if you already have a crawl space underneath your home.

Extra Storage Space

If your bedroom closets are overflowing with extra baby stuff, clothes, or holiday decorations, a new basement can give you a significant storage boost.

Living or Entertaining Space

Basements also allow people to hang downstairs and away from the kitchen while you’re prepping dinner. An added bonus: The concrete walls offer good soundproofing for your kiddos’ drum set and act as a perfect overflow room during large parties.

Increase in Home Value

Because you’re creating additional square footage, you’re likely going to see an increase in the value of your home. However, you will need to waterproof your basement to ensure it retains that value. To keep things dry, the cost of waterproofing a basement can run an additional $20,000.

“Basements are often below the water table, so waterproofing is key,” says Bob Tschudi, Angi Expert Review Board member and general contractor in Raleigh, NC. “Keeping water out involves a combination of waterproofing and water-pumping. Fortunately, there are ways to keep your basement dry in many places.”

Negatives of Adding a Basement to a House

While basements bring plenty of benefits, they do come with some drawbacks. You need to consider flooding, the initial construction costs, and whether it’s even possible to build one in your home.

Not Possible in Some Areas

In states such as Florida and Georgia, you’re unlikely to find any basements at all. This is because both the climate and local aquifers make it impossible to build more than a few feet into the ground.

The soil in these areas is also prone to shifting, making the basement likely to collapse. These areas also tend to experience high amounts of rain, so you’ll need to look into tips to prevent basement flooding.

Unfinished basement under construction
Photo: Jason / Adobe Stock

High Cost to Build

While adding on a basement to an existing house does increase its value, it’s not likely going to recuperate the initial cost to add on. The average cost to build a full basement is around $110,000 for 2,000 square feet if there’s no existing crawl space. If there is an existing crawl space or even a partial basement, the cost is closer to $45,000 for 2,000 square feet.

This doesn’t include the cost of finishing the basement, which is typically around $20,000 for the inside and around $10,000 for waterproofing the outside. You’ll also want to add in flooring, have your HVAC system hooked up, and ensure the walls are complete. Some flooring options perfect for basements include vinyl, ceramic tile, and stone tile.

Attracts Pests

While the scary stories you were told as a kid about spooky monsters in the basement weren’t true, the basement is an ideal spot for pests. The high moisture combined with low lighting makes basements a prime candidate for all the creepy crawlies and critters if not sealed properly.

Alternatives to Adding a Basement to a House

So, if you’re still undecided about whether you should add a basement, there are a few other options you can consider to accomplish your goal of additional space.

Home Addition

The cost to build on a home addition is around $140 per square foot on average. So if you only need around 200 square feet of extra space added on, you’re looking at spending around $28,000.

Converted Attic

Maybe you consider the attic an unused space. If you can’t build down, why not look into building up? The average cost to convert and finish an attic into a bedroom is around $19,000, depending on the square footage.

Who Should Add a Basement to a House?

If you’re looking to maximize the amount of space in your existing home and you don’t plan on leaving anytime soon, you might want to consider adding a basement. You’re going to get the most square footage possible, and you don’t need to deal with the stress of moving into a bigger home.

However, if you live in warmer regions, a basement may not even be an option for you. You also need to put a hefty amount toward getting a basement, so if you only need an extra bedroom, then adding another room or finishing the attic is a better option for you.

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