Now that everyone is settling into working and spending substantial amounts of time at home for the foreseeable future, we are experiencing an increased interest in basement projects for people looking to create additional working or living space within their homes. There are a variety of issues one should consider, however, in the process of determining if this type of work makes sense for you. Cost, feasibility, and practicality are important considerations before launching forward into the world of basement renovation.
Is it feasible to dig out my basement?
All basements can be dug out, but vary substantially in terms of the amount of quality useable space that can be created, and the difficulty (aka the cost) of creating that space. The least practical projects are small houses on level lots with shallow crawlspaces.
The amount of excavation is extreme and expensive. Since the foundations will be tall with mostly concrete as the outside walls, there will be little space in which to add windows.
If bedrooms are contemplated, they will require larger egress windows, which will not be feasible. And the smaller square footage will be more expensive, as the cost per foot will go down as the size of the project increases. Houses on sloped lots are generally better candidates. These homes typically have taller existing crawlspaces, or basements, requiring less excavation and allowing taller windows.
Other considerations are important. What is the access to the crawlspace? Being able to drive a Bobcat into an existing garage to start digging is much easier than having to move dirt by hand from the back of the house with buckets and wheelbarrows or conveyors. It can literally add 50% to the time and cost to complete a project on a difficult site where the home is far from the street with limited access or space along the sides of the property and multiple sets of stairs. Given the large amounts of materials and debris that need to be transported in and out of the work area, this is an important but often undervalued element in overall cost.
What types of new spaces do I want to create?
The use of the new space is another important aspect. Most people opt to create habitable space (vs. non habitable) space, which means the space must meet the proper height, insulation, heating and light requirements for living spaces, which will then allow you to count the new square footage towards the value of your home. If this is to be rental space (ADU), there are zoning rules that can affect the use of the space, and whether new bedrooms, bathrooms and kitchens are allowed, etc. Fortunately, most cities have liberalized their policies regarding the use of basement spaces and related parking requirements based upon the number of bedrooms.
One of your first steps should be to measure the space that you will be adding and to layout the various rooms you want to create with their approximate sizes. Common layouts include a bedroom or two, large family room, bathroom, laundry, home office and mechanical room. If stairs are to be added connecting to the main floor above, there has to be an appropriate location with sufficient length for them to be installed that won’t adversely affect the upstairs floor plan. Keep in mind the height of the foundations in the new space as that will determine window sizes and locations.
The parts of the job you probably weren’t thinking about can be a big deal.
Since basements normally have most of the home’s utilities running through them, these generally have to be relocated as part of the job. Often the house will need to be partially or completely rewired, along with adding new plumbing and mechanical work for the new layout of the basement. A zoned heating and cooling system allows for the fact that the lower level is generally much cooler than the upstairs. Typically, utilities are consolidated into a new mechanical area along with any new baths and a laundry, and soffits are created to house ductwork. Often, a new sewer lateral needs to be added if the drains are not in the correct location. The new layout may require structural changes depending on the new wall locations, including the addition of structural beams and new piers. Drainage around the outside of the new foundations and waterproofing on the inside of them are critical to avoid dampness and mold issues in the future. Additionally, soundproofing is often added at the basement ceiling to isolate the downstairs more effectively from the space above.
The furnace was located to this utility closet with an adjacent laundry area and sink in the owner’s new art room. The ceiling in this room had to be lowered from 8’ to 7’ to accommodate all the new ductwork feeding the upstairs and downstairs. In the photo on the right, the owner’s new space steps up into the back portion of the basement, the apartment for Mom.