How to Calculate the Cost of Building a Basement

All sound construction projects begin with working everything out on paper -- developing a budget and blueprint -- to help you estimate the costs and the time it will take to complete the project. The budget can also double as a project plan, by helping you to anticipate the individual phases of construction.

The more than you can plan for on paper, the better prepared you are to deal with any surprises that may come up. If you create a budget in a spreadsheet or worksheet, it can also help you keep track of your expenses as you go. The categories you need to add to calculate the cost of building a basement include:

  • Design and engineering fees
  • Building and permit fees
  • Soil and grading costs
  • Foundation and footings
  • Building materials
  • Plumbing and electrical
  • Miscellaneous supplies
  • Finish materials
  • Labor fees
  • Contingency account

Design and Engineering Fees

Before you can build any residential or commercial project, you need to have a solid design and blueprints -- in some building jurisdictions -- and the plans engineered, especially when soil tests indicate this need. You will need to present to the local authorities a design that includes blueprints and detailed information on your building project. The architect or engineer chosen for the project must have an understanding of local conservation, environment, zoning and building code requirements. The finished blueprint includes the size of the basement such as wall heights, lengths and widths along with total square footage -- all of which drive material costs.

Permit Fees

To calculate the permit fees, you need to contact your local building authority. In some areas of the country, building authorities may require separate permits for various phases of construction, such as one for grading, building, plumbing or electrical -- or they may roll these all up into the one fee. The local agency can provide you a list of permits needed and the fees for each. Local fees may also include taxes for impacts to schools, roads and fire services, depending on where you live.

Soil and Grading

Because building a basement requires excavation -- removing dirt from the ground -- the local authority generally requires you to perform soil tests before you can break ground to determine the soil's components. The results from these tests can influence the materials you choose to build your basement. The project may also call for a surveyor to accurately set the site up for grading. All basements require a grader to excavate the site to create the space to build.

Foundation and Footings

Unless you're building an underground shelter of some sort, basements double as the foundation for the structure above it. All foundations made from block or cement also require footings beneath the ground engineered to support the weight of the structure. The results in the soil tests can impact how the foundation and footings are constructed. Foundation and footings also include costs for gravel, sand and rebar as part of its support.

Building Materials List

Research the costs of building materials needed for the project so that you can price out these components individually. After the basement has been designed and blueprinted, the architect or engineer should also include a materials lists that details everything needed to complete the project. Use this list to determine how much the materials will cost. This should include cement or block for the exterior walls, interior stud framing -- lumber, fasteners, drywall and doors -- if you are planning to divide the basement space into separate rooms, any exterior above-grade windows or doors as well as any waterproofing needed. You may also need to incorporate costs for drainage around the foundation of the basement or sump pumps depending on where you live and the ground's makeup.

Plumbing and Electrical

When you want to add a small kitchen or a bathroom to the basement, don't forget to incorporate the costs for water supply lines, drains and vents as well as plumbing fixtures -- sinks, toilets, tubs or showers. Some people opt to put their laundry room in the basement; you'll need to provide the needed hookups for all appliances: hot water heater and heating or air conditioning as well as ducting, light fixtures and electrical outlets.

Miscellaneous Supplies

Every construction project has a list of miscellaneous supplies that you need to complete the structure. For a basement, calculate the costs for waterproofing </ahref="http:>it, foam insulation, vapor barriers, caulking or fasteners.

Finish Materials

The finish materials include cabinetry, countertops, paint, wall, door and window trim, drop ceilings -- if planned for -- and flooring materials such as carpet, vinyl or tile; all the supplies you need to make the basement a usable space.

Labor Costs

Many contractors don't break out their labor costs individually when providing you with a bid. For example, grading bids generally break out the setup fee as a separate line item -- transporting the grader to the site and setting it up -- and include either an hourly figure or a by-the-job estimate that includes both the machine and the labor to operate it. You may also want to contract out only portions of the project to professionals -- such as the grading and exterior wall construction -- and finish the rest of the basement yourself if you have the experience. This can help you to keep labor costs and overall project costs down.

Contingency Account

As a safety factor, add a contingency account that represents 5 percent to 10 percent of the overall budget. This gives you wiggle room for cost overruns, unplanned costs or surprises.