Finishing or remodeling a basement serves a dual purpose of providing more usable living space in a home and helping increase the home’s value. Finishing a basement costs about $25–$50 per square foot, depending on how the basement is finished, whether any challenges come up or whether there are special circumstances with the project. A 1,000-square-foot basement can cost up to $50,000 to finish. Virgil Miranda of Virgil Miranda’s Construction, a general contracting company based in New Bedford, Massachusetts, says it can be tricky to estimate remodeling jobs based on square footage, but using that number is an easy way for homeowners to know what they’re getting into.
Finish versus remodel
Finishing a basement in a newer home that has plumbing and electrical roughed in, a watertight foundation and some insulation installed usually costs less than remodeling an already finished basement. In the latter case, demolition at the beginning of the project will add $500–$1,500 to overall costs.
Waterproofing and moisture control
Because basements are typically below ground level, contractors must address any water seepage or moisture collection issues. Prior to creating a project bid, most contractors will inspect the area to check the interior floor and walls for dampness and make sure the exterior of the foundation is in good shape. Homeowners can clear downspouts and gutters of debris to ensure that they help keep moisture away from the foundation. Depending on how watertight the basement and foundation are, it may be necessary to protect the basement from water future damage after it’s finished. This work can cost anywhere from $700-$3,000, depending on what needs to be done.
City building permits and inspections may be required to ensure that a basement refinishing project meets building code requirements—especially if a bathroom or kitchenette is added. Most contractors take care of pulling the permits and scheduling inspections and add the cost to the final bill.
If the basement space is open—without any separation of rooms—the contractor will need to do the interior framing necessary to define the rooms and spaces. A ballpark cost for framing in a 1,000-square foot basement is $1,000, but this can vary depending on the layout of the basement and any existing structural issues.
Installing a bathroom in a basement costs more than installing a bathroom above ground. Costs can range from $2,500 to $5,000, depending on the number of fixtures and whether the plumbing must be installed from scratch or if it’s roughed in already. Basement plumbing requires special considerations to ensure proper drainage and tie-in with the main sewer line, which may not be deep enough to allow the basement bathroom plumbing to use gravity the way above-ground plumbing does. Virgil Miranda’s Construction subcontracts all plumbing work. Miranda says that sometimes the toilet alone in a basement can cost up to $2,500 because sometimes homeowners need to invest in a toilet that does not use gravity but instead a macerating function to grind waste down to prevent clogging. Miranda estimates that each bathroom fixture in a basement costs $800–$900 on average, so a full three-piece bath could cost $3,000 for the fixtures alone. Adding a kitchenette or wet bar sink adds more to overall refinishing costs. In addition, some basements require a French drain with one or more sump pumps, which can cost up to $10,000, depending on how much ground the drain covers.
Because they lack natural light, basements require extra attention to lighting from artificial sources. Installing electrical outlets and lighting in a standard basement costs $1,000–$1,500, plus the costs of fixtures and switches.
Audio-visual and home theater
Basements converted into game rooms or home theaters may include special audio-visual features that will be part of the electrical finishing. These additions can cost a few hundred dollars or a couple thousand, depending on the exact setup.
Flooring in a basement sometimes requires special consideration because of the below-ground location. Before the flooring goes down, the contractor may install a layer that acts as a moisture barrier, such as dimpled polyethylene. Carpet or vinyl flooring can cost about $1,500 for an average basement and hardwood can cost up to $4,000.
Doors and trim
Miranda of Virgil Miranda’s Construction says he typically charges $1.25 per linear square foot to install baseboards and trim and $125 per door, not including materials costs.