How much does it cost to dig out a basement?
How much does it cost to dig out a basement?
$50 – $100 per square foot
$50,000 – $200,000 cost to convert crawlspace to finished basement
$10,000 – $30,000 cost to dig out basement for new house
Basement dig out cost vs. crawl space conversion
Digging out a basement for a new construction costs $10,000 to $30,000. The cost to convert a crawlspace into a finished basement is $50,000 to $200,000 or $50 to $100 per square foot. Adding a basement to an existing house typically requires excavation and underpinning to lower the floor.
| Project | Average cost |
|---|---|
| Convert a crawlspace to a finished basement | $50,000 – $200,000 |
| Expand a partial basement to full | $20,000 – $80,000 |
| Deepen an existing basement by 1 to 2 feet | $40,000 – $90,000 |
| Dig out a basement for new construction | $10,000 – $30,000 |
Cost to dig out a basement by size & project
The following costs are to dig out a basement and finish the space.
| Basement size (square feet) | Average cost |
|---|---|
| 800 | $40,000 – $80,000 |
| 1,000 | $50,000 – $100,000 |
| 1,200 | $60,000 – $120,000 |
| 1,500 | $75,000 – $150,000 |
| 2,000 | $100,000 – $200,000 |
| 2,400 | $120,000 – $240,000 |
*Cost data is from research and project costs reported by HomeGuide members.
Underpinning cost to lower basement floor
Underpinning a foundation costs $10,000 to $30,000+ on average. Underpinning includes:
Removing the old floor
Digging underneath
Adding supports
Pouring new concrete floor and walls for a basement
Basement foundation benching cost
Foundation benching costs $20,000 to $35,000. Benching involves building a concrete ledge or "bench" around the basement's inner walls, lowering the foundation within the benched space, and pouring a new concrete floor at a lower depth.
This method is faster and less expensive than underpinning because it does not remove the existing soil or foundation footing. However, the bench around the perimeter reduces the basement's square footage.
Cost to add a basement by raising a house
The cost to raise a house is $10,000 to $40,000 just to elevate or $40,000 to $150,000 to lift a house and build a basement underneath, including finishing the interior. This method costs more than underpinning or benching but does not require as much excavation.
Crawl space excavation costs for basement
Crawlspace excavation costs $20,000 to $45,000 for digging and leveling alone, depending on the soil type and the basement depth.
Cost to convert a crawlspace to a full basement
| Service | Average cost |
|---|---|
| Raising or underpinning and bracing | $20,000 – $50,000 |
| Excavation | $20,000 – $45,000 |
| Installing plumbing and drainage | $6,300 – $17,000 |
| Pouring foundation | $5,000 – $19,000 |
| Finishing | $22,000 – $46,000 |
The following factors affect the cost:
Size & depth – Most basements are 8 feet tall and 1,000 to 2,000 square feet. Adding a larger or deeper basement increases costs.
Soil type – Sand, silt, and loam are easier and cheaper to remove than clay or rocky soil.
Permits – Construction permits cost $500 to $2,000 on average, depending on the project’s total value or square footage.
Insurance – Adding a basement involves major structural changes. Make sure your insurance plan covers the changes and any potential repairs.
Basement drainage and plumbing
The following costs may apply to installing drainage and plumbing under a new foundation:
Plumbing installation costs $450 to $1,800 per fixture or $2,300 to $5,000 total on average.
Drainage installation costs $4,000 to $12,000 or $40 to $85 per linear foot for a basement perimeter drain.
The cost to waterproof a basement is $4,500 to $15,000 on average or $6 to $15 per square foot.
Pouring basement foundation
Pouring a basement foundation costs $26,800 to $80,500 or $30 to $35 per square foot, not including finishing the basement's interior. Contractors pour the new foundation after digging and installing plumbing.
Cost to add a finished basement
Finishing a basement costs $22,000 to $46,000 and includes the following costs:
Basement insulation costs $600 to $4,600 on average.
Basement framing costs $2,300 to $6,000, depending on the square footage and layout.
Drywall installation costs $1,500 to $7,000 total for a 1,000 square foot basement or $1.50 to $3.50 per square foot.
Interior painting costs $350 to $850 per room or $1 to $3 per square foot.
Flooring installation costs $4 to $15 per square foot, depending on the material.
Basement rewiring costs $800 to $1,500 for a 1,000 square foot area.
A walkout basement or mother-in-law apartment may add more value to a home than other basement styles.
Alternative costs to digging an existing basement deeper
A home addition costs $22,500 to $74,000 on average and is a less expensive way to add square footage to an existing house than digging a basement.
Cost to finish a crawl space
Crawlspace encapsulation costs $3,000 to $8,000 or $3 to $7 per square foot and typically includes cleaning, sealing, vapor barrier installation, a sump pump, insulation, and a dehumidifier. Encapsulation prevents mold growth, pests, and pollutants.
Cost to dig a basement for new construction
Digging a basement for a new construction costs $10,000 to $30,000 for the excavation alone, compared to digging beneath a crawlspace or an existing basement.
Pros and cons of basement excavation
| Pros | Cons |
|---|---|
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Frequently asked questions
Can an existing basement be dug deeper?
Yes, it’s possible to lower an existing basement. Deepening an existing basement by 1 to 2 feet costs $40,000 to $90,000 on average, including excavation and a new concrete floor.
Is it worth it to dig out a basement?
Digging out a basement increases a home's square footage and resale value, especially if the basement is walkout or rental space. However, the project is expensive and may not provide enough return on investment (ROI) to be worth it.
Consider a home addition as a less costly way to add square footage if yard space is available.
How long does it take to dig out and lower a basement?
Digging out and lowering a basement takes 2 to 5 weeks, or several months if there are any major obstacles.
Getting estimates and hiring basement dig out contractors
Before hiring a contractor to dig out a basement, be sure to:
Get at least three detailed estimates to compare.
Hire a company that is licensed, bonded, insured, and has been in business at least five years.
Browse their reviews on HomeGuide and Google.
Ask for references with contact information.
Ask for a portfolio of past renovation projects.
Get a detailed contract and warranty in writing before the work begins.
Never pay in full before the project is complete.
Questions to ask
What experience do you have digging basements?
Are you licensed, bonded, and insured?
What does the estimate include?
What additional costs should I expect?
How long will the project take?
What permits do I need, and will you obtain them?
How do you handle any on-the-job damage?