How Deep Can You Dig A Basement?

Kerry Souder
by Kerry Souder

Having a basement offers more storage space and additional living space for you and your family, which makes it a popular project for many homeowners, especially if you don’t have a lot of overall square footage. Depending on where you live, you’re going to run into different guidelines and roadblocks when it comes to digging out a basement.

That said, we’re going to do our best to help you understand a bit more about the project, so you can meet your unique wants and needs for your home. So, how deep can you dig a basement?

Depending on where you live, you can dig a basement between 7 feet to 25 feet. That said, it is crucial to hire a professional inspector to make sure your land is suited for the project. Most basements in the U.S. aren’t as deep due to regulations for an additional exit out of the basement, environmental factors, and drainage issues.

In this article, we’re going to go over why you can’t dig your basement out too deep, how much the project costs, the average basement size in the U.S., and more. That way, you can have plenty of useful information to start planning your basement construction project.

Why Can’t You Dig a Basement Too Deep?

There are a few factors that go into deciding how deep a basement can be, and it’s important to consider them all before you plan your project. Otherwise, you risk running into issues down the road, including your basement sinking further into the ground. Many of the guidelines that will dictate your basement construction project will depend on where you live, but these are three things that you will absolutely have to be on your mind.

Secondary Emergency Exit

Due to the current safety standards in the United States, most basements won’t be deeper than one floor. According to the International Residential Code, each basement level needs to have at least one additional exit route other than the interior staircase. This is usually an egress window or a separate door and staircase that leads directly outside. This secondary exit must lead either directly to a public way or onto a yard that leads there.

Environmental Reasons

Where you live is going to have a big impact on how deep you can dig out your basement. Before you consider digging out a basement, be sure to get in touch with local builders and inspectors to ensure your property is able to accommodate this extra space underneath your home.

For example, many neighborhoods in California and New York have houses built on bedrock, which is impossible to dig deep into. In other places like Chicago, you have to deal with a high water table. That said, digging a basement will pose too much risk for water damage.

Water Damage and Drainage Issues

If you live near water or deal with many storms, having a basement can lead to drainage issues. Even basements with functioning floor drains may not be able to handle the threat of water taking over the space if your home is constantly impacted by water.

Average Basement Size in the United States

Basement sizes in the United States can vary depending on when the home was built and the set-up of the house in general. However, the average basement is between 7 and 8 feet high for most new construction projects.

How Much Does It Cost to Make a Basement Deeper?

The cost to add a basement to a home that did not have one can cost you anywhere from $30,000 to $50,000, but what if you want to simply dig a basement deeper? Depending on the extent of the project, you can expect digging out a basement to cost anywhere from $10,000 all the way to $100,000. For the average project, you can expect to pay between $30 and $75 per square foot.

Can You Have a 2-Level Basement?

Some homeowners want to add a sub-basement in their home for additional storage space or usable space for a wine cellar, a pantry, or anything in between. Some homeowners also may store their boilers or furnaces there.

You can add a sub-basement to your existing basement, but you have to consider a handful of different factors before starting the project. Otherwise, you risk damaging your basement and potentially your home’s entire foundation. For this reason, you should always consult with a professional. Here are the things you need to consider before installing a sub-level basement:

  • Topography. The size of your sub-basement will depend on where your house is situated. Different ground levels will impact ventilation and light levels.
  • Geology. A building official will need to test the ground conditions around your home, so you’re aware of the groundwater level and soil type. For example, you will not be able to dig deeper into solid rock to construct a sub-basement.
  • Property structure. Your home’s foundation will play a big role in if you can even have a sub-basement. It needs to be fully secure with no threat of destabilizing.
  • Drainage. If you’re planning to have a bathroom in your sub-basement, you will have to consider the plumbing situation and waste drainage capabilities.
  • Access. Construction workers will need enough room around your property to finish the project. You will have to get the right documentation for this and may have to talk to your neighbors, too.
  • Fire escapes. Your sub-basement needs to have a fire escape or egress. If you have an egress in the main basement, you will still need an independent exit that goes all the way to the ground.

Other Common Regulations for Concrete Basements in The U.S.

When building a basement, it’s important to pay attention to local regulations to ensure you do everything correctly. The following points are more of a guideline that apply to most residential basement projects. That said, building codes can vary depending on where you live.

Size and Ceiling Height

When constructing a basement, you have to follow guidelines about what is considered a habitable room. For basements, this involves the area being 70 square feet or larger. It also cannot be smaller than 7 feet in height or width.

Furthermore, finished box-outs for beams, cutwork, plumbing, or electrical systems should have a minimum clearance of 6’6”. A professional inspector will be able to help you figure out these dimensions and any other sizing guidelines.


Concrete walls in your basement that are less than 50% above grade should have an insulation level of at least R-8 that extends down to the basement floor. Conversely, basement walls that have more than 50% above grade should have at least R-13. The exception to this rule is if your foundation walls have less than 20% exposure. These walls may be uninsulated.

Natural Light and Ventilation

For a room to be habitable, any glass areas (i.e., windows) can’t be less than 8% of the floor area. At least half of this space must have unobstructed ventilation with screens included. Should you not have enough space for windows of this size, you may be able to use artificial lights or mechanical ventilation.

The emergency escape window also needs to be operable from the inside without any special circumstances. Basically, this means anyone has to be able to open this window without exerting force or using a tool of some sort.

Basement Stairs and Emergency Exits

Any stairways leading into the basement need to have solid risers or toe boards and sturdy handrails. Any guards that are on the open side of the stairs should be 34 inches high at a minimum. They also need to have balusters spaced 4 inches apart or closer. These stipulations will be different for walkout basements.

That said, you will need a secondary emergency exit from your basement regardless of what type of basement you have.

So, How Deep Can You Dig a Basement Out?

Technically, you may be able to dig a basement out up to 25 feet. However, odds are, the ground around your home will deter you from doing so. Most basements in the United States are between 7 and 8 feet high. Some may be higher if you decide to add a sub-basement. Be sure to get in touch with a professional inspector and builder before moving forward.

Kerry Souder
Kerry Souder

I am a copywriter and editor based in the Las Vegas area with nearly a decade of experience under my belt writing landing pages, cost guides, blog posts, newsletters, case studies, and social media content. I have a degree in Strategic Communication and experience working in both the account and creative spheres. My goal is to always be discovering new interests and bettering myself as a writer and editor along the way.

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