If you want to expand your home, you have options other than building an addition or adding a story. An additional way to increase your home’s livable space is to excavate a basement or convert a crawl space into a finished basement. The total cost to dig out and finish a basement is typically between $60,000 and $150,000, and the cost to expand a crawl space ranges from about $47,500 to $135,000.*

*Unless otherwise noted, cost figures throughout this article were pulled from Angi and HomeAdvisor.

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What Are the Differences Between Basement Excavation vs. Crawl Space Conversion?

Excavating a basement is slightly more expensive than expanding an existing crawl space. It costs around $22,500–$45,000 to dig out a brand-new basement. Comparatively, the digging required for crawl space expansion costs around $10,000–$30,000. 

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What Factors Affect the Cost Of Digging Out a Basement?

Here are the primary factors that determine the total cost of a basement excavation project.

• Size of excavation: The larger the space you need to have excavated, the more the project will cost.
• Raising or bracing: Raising your home on jacks will be less expensive but also less stable than bracing it.
• Plumbing: Your new basement will need proper plumbing and drainage systems.
• Permits: Local building codes will determine how much you’ll pay in permit costs.
• Foundation: A new concrete foundation will need to be poured under your new basement.

Cost by Size of Excavation

The digging itself is the largest contributor to basement excavation costs since you’ll pay between $75 and $150 per cubic yard of dirt removed. Creating a 1,000-square-foot basement requires excavating about 300 cubic yards, so you’ll likely pay between $22,500 and $45,000 for the digging alone.

Cost of Raising or Bracing the Home

A house needs support when the earth underneath is excavated to create a basement. One way to support a home is to raise it on hydraulic jacks. While this is the quicker and less expensive option at $3,100–$9,400, it also subjects the home’s structure to substantial stress, potentially causing cracks or other damage to the walls, floors, or ceilings. Your home may need to pass structural checks to determine whether it’s safe to raise.

Alternatively, you can have your home braced along the foundation footing while the digging takes place underneath. This process is called underpinning and requires more time and labor, so it can add up to $20,000 to the project. However, it preserves some of the structural integrity of the house and reduces risk. You’ll want to speak to a structural engineer about the best process for your home.

Cost of Plumbing and Water Control

To make your new basement space livable, you’ll need to install new plumbing. In addition, you’ll need drainage and waterproofing to keep your basement dry if you live in an area with a high water table.

• Plumbing: Depending on the fixtures you want in your basement and how the excavation affects the main sewer line, you may pay anywhere from $1,000–$3,000 for plumbing. 
• Drainage: The drainage system you need will depend on the local climate and soil conditions, plus the grading of your yard. It will likely cost between $2,000 and $6,000.

Cost of Engineering

Whether you’re raising a house, installing piles, or bracing the foundation with underpinning, make sure that the soil is assessed and the foundation gets designed by a professional structural engineer. There are inherent risks with all methods of foundation expansion and reinforcement, and each situation requires design and load calculations provided by engineers.

If you don’t have access to a structural engineer, consult with your foundation contractor. Be aware of the risks of home damage during and after construction, and be proactive in both design and the contract with your builder. Engineering will often be a small percentage of the project’s total cost, generally running in the thousands of dollars.

Cost of Permits

This major construction project will require building permits no matter where you live. However, the specific permits and their costs will vary based on your city and state. Prepare to pay between $1,200 and $2,000 for permits.

Cost of New Foundation

Once the engineering is completed, the permit is obtained, and a contract has been signed, your home will need a new foundation. The price of a foundation for footings, walls, and the cost of pouring a concrete slab is usually between $10,000 and $30,000.

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Additional Cost Considerations for Digging Out a Basement

In addition to the factors above, some other considerations may raise the project cost.

Adding a Basement Below an Addition

Construction of an aboveground addition to your home is nearly always cheaper than digging a basement under an existing foundation—usually costing between $21,000 and $73,000. If you are planning an addition, consider adding a partial basement to the plans. Excavation as part of new construction is a far easier prospect than jacking up or underpinning your home.

Finishing Your Basement

You can use an unfinished basement for storage space, but if you want it to qualify as extra living space, you’ll need to finish the basement. The cost to finish a basement is usually between $7 and $23 per square foot and may include flooring, HVAC additions, plumbing, electrical, drywall, painting, and egress window installation.

• Flooring: The price of your finished basement floor will primarily depend on the material you choose. Including installation, hardwood flooring costs $6–$18 per square foot, carpet installation costs $5–$11 per square foot, and vinyl tile floor costs $2–$14 per square foot.
• Electrical: Your basement will need all new wiring, and hiring an electrician costs $40–$120 per hour.
• Drywall: Hanging new drywall will typically run between $1.50 and $3 per square foot. Remember that this applies to the walls’ area, not the floor’s square footage.
• Painting: Of course, you can paint the new basement space yourself, but if you want to hire a pro, interior painting costs $1,000–$4,000 for a 1,000-square-foot area.
• Egress window: If you want to use the new basement as a bedroom, you’ll need to install a window big enough to be used as an emergency exit. Egress windows cost $2,500–$5,300 each.

Walkout Basement

A walkout basement has at least one completely above-grade wall so that someone in the basement can open the door and walk out into the yard. Not every property is suitable for this type of basement since it requires a sloped lot. Adding a walkout door to an existing basement will cost $2,500–$10,000, but creating an entirely new walkout basement is likely to reach the higher end of the basement excavation price range.

Unexpected Repairs

Since excavating a basement or expanding a crawl space involves foundation work and alters your home’s structure, the potential for unexpected repair costs is high. If the contractors find substantial cracks or unevenness in your foundation, you will likely pay $2,100–$7,800 for foundation repair. If your house sustains damage from the raising process, you may need to repair the drywall or the frame at a cost of $50–$80 per square foot. This is one project where it pays to leave substantial overage space in your budget.

Homeowners Insurance

Your homeowners insurance premiums may increase if the additional space in your new basement is considered official square footage. Talk to your insurance agent about a possible increase as well as potential coverage for your home should something go wrong during or after the excavation process.

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Is Adding a Basement Worth It?

Adding a new basement to an existing home is a significant expense and a disruptive project. The house could become uninhabitable during the process, which can easily take months to complete. You’ll need to carefully weigh the project’s cost against an expanded living space and increased home value. Here are some factors to consider when deciding whether this project is right for you.

• The return on investment (ROI) of a fully finished basement is around 70%, according to Zillow, but that applies to the cost of an existing basement remodel, not the digging of a new one. This is a rare enough project that there’s little data readily available on a specific ROI.
• You won’t receive the full value of the new basement unless you finish the space. Budgeting for and designing a finished basement from the outset is your best bet.
• Talk to your local planning department and tax assessor about whether the finished basement space will count toward your home’s official square footage and what the implications are.
• Keep your home’s landscaping in mind. If you have trees or shrubs near your home, you may need to alter the landscape substantially to complete the project.
• Remember that building up or out is almost always going to be cheaper and easier than expanding under an existing home.

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Should You DIY vs. Professional Basement Excavation?

Simply put, digging out a basement under a home on your own is a bad idea. Some environmental safety experts regard excavation as the most dangerous type of construction project. Even if you could rent the necessary heavy equipment, the risk to your safety and your home’s structural integrity is large.

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Our Conclusion

Creating a basement under a house that doesn’t already have one is an expensive, time-consuming, and risky project. However, if you want to expand your home but can’t build up or out, excavating a basement or converting a crawl space is your best bet short of moving to a new house. If you’re thinking about adding a basement, plan, and budget carefully, consulting with experts every step of the way so you’re in for as few surprises as possible.

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FAQ About the Cost Of Digging Out a Basement

How do you excavate a basement under an existing house?

Contractors excavate a basement by first supporting the house by either raising it on jacks or underpinning it. Then, they use heavy machinery such as a backhoe or Bobcat to excavate the space. They then pour concrete walls and a concrete floor to serve as the new foundation.

What is the deepest you can dig a basement?

According to U.S. residential building codes, you can only dig a basement that’s one floor deep. Usually, that equates to a ceiling height of about 8 to 10 feet.

Can you dig a basement next to an existing house?

You can dig a basement alongside an existing house, but only under certain conditions. The soil needs to be the right consistency and free of bedrock, and your home needs to be structurally sound since the current foundation will be undermined when you dig next to it.

Can you turn a crawl space into a full basement?

Yes, a crawl space can be converted into a full basement. The process is similar to the situation described above but generally requires slightly less excavating as some space is already free of soil.

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