It May Be Cheap Living Space, but There Are Special Codes and Considerations
Some conditions are intensified below grade
Turning an unfinished basement into additional living space is one of the least expensive ways to make a customer's house bigger and greener. At the same time, basements pose some unique challenges in terms of air quality, natural lighting, insulation, and moisture control. In some parts the country, radon could be a problem, while in all locations, there are codes that address egress windows.
Turning an unused below-grade basement into a living space is a greener move than adding on.
By their nature, basements have inherently higher moisture levels, less natural light, and limited ventilation--all which must be overcome to turn a below grade space into a above average living area.
Codes also may require a minimum floor-to-ceiling height. Concealing overhead ducts and plumbing, or adding rigid insulation and sleepers to the floor, can made it tough to meet the standards. Other codes and considerations also apply.
Windows bring in natural light, often in short supply in a basement, but with them come energy and moisture issues. When a basement will be used as a home office, a family room or especially a bedroom, building codes typically require some means of getting in and out in an emergency. Windows used for this purpose are called egress windows, and they must meet minimum size requirements Larger windows may require wells that come with their own set of requirements.
This problem of radon, a naturally occurring radioactive gas, is a common one among properties in some parts of the country. But there are other potential contaminants in basements: lead, mold, creosote, pesticides, and asbestos. Removing or encapsulating these materials is important and often requires the help of a professional abatement company.
Increasing the energy efficiency of the building envelope can create a basement moisture problem where there was none before. Energy flowing through a structure tends to dry things out. A home's moisture equilibrium can be upset when the basement is made more energy efficient and energy flows are reduced through finishing. Moisture management involves assessing gutters and downspouts, finished grade, foundation damp-proofing and perimeter drains, and whether there is free-draining fill and a capillary break (a barrier that is wide enough to prevent moisture from moving through it) beneath the slab. Some of these things can be checked by a visual inspection during a heavy rain, with moisture meters and with a plastic-sheet or calcium chloride test as described in ASTM standards.
Efficient heating and hot water
Finishing a basement doesn’t necessarily include replacing a furnace, boiler, or water heater. But older fuel-burning equipment can be a concern. Modern sealed-combustion appliances draw air from the outside into a combustion chamber that is completely separated from inside air, eliminating concerns about backdrafting. They’re also more energy efficient, usually take up less space and don’t have to be located next to a masonry chimney.
Insulate the basement floor and walls. Include a capillary break between all concrete and sill plates. Air seal and insulate rim joist areas.
Install smoke and carbon monoxide alarms. Consider installing equipment for ventilation and humidity control.
Insulate the water heater and hot water pipes.
Provide an appropriate mix of color-correct ambient and task lighting. Install energy-efficient lighting. Provide natural light.
Install hard-surface finish flooring. Avoid carpeting in high moisture areas or where spills could occur. Choose area rugs over wall-to-wall carpeting.
Walls and ceilings
Don’t use paper-faced gypsum drywall in damp areas. Limit the use of wall coverings in high moisture areas. Use low- or zero-VOC paints and finishes, sealants, caulks and adhesives.
Furniture and fittings
Choose furniture and fittings that don’t absorb moisture. Avoid cabinetry and furniture made from particleboard or medium-density fiberboard (MDF), which won't last in damp areas. Where moisture is a problem, avoid fully upholstered furniture.
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