How Much to Dig a Basement Under Existing House

How Much to Dig a Basement Under Existing House

Are you considering adding a basement to your existing house? It’s important to understand the cost factors involved in this major construction project. From excavation to plumbing and permits, each aspect contributes to the overall expense. In this article, I will break down the cost considerations and provide valuable insights to help you plan your basement excavation.

Key Takeaways:

  • The total cost of digging out and finishing a basement under an existing house typically ranges from $60,000 to $150,000.
  • Excavation costs make up a significant portion of the total expenses, averaging $75 to $150 per cubic yard of dirt removed.
  • Raising the house on jacks is a less expensive option, but bracing provides greater stability.
  • Plumbing and drainage systems, as well as building permits, are additional factors that affect the cost.
  • Considerations such as adding a basement below an addition, finishing the basement, and creating a walkout basement can increase the project cost.

Factors Affecting the Cost To Dig Out a Basement

The cost to dig out a basement is influenced by several factors that homeowners should consider when planning this type of project. Understanding these factors can help ensure a more accurate budget estimate and avoid any surprises along the way.

Size of the Excavation

The size of the excavation is a major consideration when calculating the cost of digging out a basement. Larger spaces will require more time, labor, and equipment, which can increase the overall cost. It is important to accurately measure and assess the dimensions of the basement area to get an estimate from contractors.

Raising or Bracing the House

The method used to support the existing house during excavation also affects the cost. Raising the house on jacks is a less expensive option, but it may result in potential damage to the structure. On the other hand, bracing the house is a more costly but safer choice that ensures the stability of the property.

Plumbing and Drainage Systems

Installing plumbing and drainage systems in the newly excavated basement is necessary for proper functionality. The complexity of these systems and their associated costs should be factored into the overall budget. Homeowners should consult with a professional plumber to determine the specific requirements and estimate the expenses.

Building Permits

Obtaining the necessary building permits is an essential step when digging out a basement. The cost of permits can vary depending on local building codes and regulations. Homeowners should contact their local municipality or building department to understand the permit requirements and associated fees.

Type of Foundation

The cost of a new foundation, including the pouring of concrete walls, floors, and footings, should also be considered. The type of foundation chosen, such as poured concrete or block, will impact the overall cost. Homeowners should consult with a professional contractor to determine the most suitable foundation type for their specific project.

Factors Average Cost Impact
Size of the Excavation Higher excavation costs for larger spaces
Raising or Bracing the House Higher cost for bracing, but increased stability
Plumbing and Drainage Systems Additional expenses for installation
Building Permits Varying permit fees depending on location
Type of Foundation Cost variation based on foundation type chosen

Additional Cost Considerations for Digging Out a Basement

In addition to the primary cost factors mentioned above, there are other considerations that can increase the project cost. One such consideration is adding a basement below an existing addition. This is usually a more cost-effective option compared to digging a basement under the main house. The size and complexity of the addition will influence the overall cost.

Another important consideration is the cost of finishing the basement to create livable space. This involves expenses such as flooring, electrical work, drywall, painting, and egress window installation. The average cost of finishing a basement can range from $7 to $23 per square foot, depending on the materials chosen and the desired level of customization.

For those looking to create a walkout basement, there will be additional costs to consider. This type of basement allows for direct access to the outside, usually through a set of doors or a sliding glass window. Installing the necessary structural components and ensuring proper drainage may add to the overall construction cost.

It is important to note that unexpected repairs can arise during the excavation process, especially in older homes. These repairs can include issues with the existing foundation, plumbing, or electrical systems. It is advisable to budget for potential repairs and include them in the overall cost estimation.

Impact on Homeowners Insurance

When undertaking a major home renovation such as digging out a basement, it is important to consider the potential impact on homeowners insurance. Adding square footage to your home can increase its value, which may result in higher insurance premiums. It is recommended to contact your insurance provider to discuss any changes to your policy, ensuring adequate coverage during and after the construction process.

By taking these additional cost considerations into account, homeowners can make informed decisions about whether digging out a basement is the right choice for their needs and budget. While the average cost of digging a basement can vary, with factors such as the size of excavation, finishing options, and additional features influencing the final price, proper planning and budgeting can help ensure a successful and cost-effective basement construction project.


How much does it cost to dig out a basement under an existing house?

The total cost typically ranges from $60,000 to $150,000.

Is excavating a basement more expensive than expanding an existing crawl space?

Yes, excavating a basement is slightly more expensive, with costs ranging from $22,500 to $45,000 for a new basement and $10,000 to $30,000 for crawl space expansion.

What factors affect the cost to dig out a basement?

Factors that affect the cost include the size of excavation, raising or bracing the house, plumbing and drainage systems, building permits, and the cost of a new foundation.

What is the average cost of digging out a basement?

The average range for the digging process is $75 to $150 per cubic yard of dirt removed.

What are the costs associated with plumbing and drainage systems for a new basement?

Plumbing costs can vary from $1,000 to $3,000, while drainage costs range from $2,000 to $6,000.

How much do building permits typically cost?

Building permits can cost between $1,200 and $2,000.

What is the cost of a new foundation?

The cost of a new foundation can range from $10,000 to $30,000.

What other cost considerations should I keep in mind?

Other cost considerations include adding a basement below an addition, finishing the basement, creating a walkout basement, unexpected repairs, and potential increases in homeowners insurance premiums.

Can I dig out a basement myself?

DIY basement excavation is not recommended due to the complexity and safety concerns involved.

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