Synopsis: If you think that your house needs more living area, you don’t necessarily have to consider the expense and hassle of an addition. Habitable space might already exist above or below your current living areas in the basement or attic of your home. Architect Jerri Holan outlines the things to keep in mind if you want to transform an attic or basement into a functional space. Holan considers not just design aspects of transforming an attic or basement space into a room but also code and structural issues. Basements, for instance, may need to correct moisture issues before they can be habitable; attics may require reinforced floor and roof framing.

Perhaps you’re wondering what it would take to make a real bedroom out of that attic space your teenager has monopolized. Or maybe you’re curious if it’s possible to transform the basement into the home office you’ve been dreaming of. You’re not alone. Attic and basement conversions are two of the most popular remodeling projects for homeowners—and for good reason. Dollar for dollar, capturing existing space that already has floors, walls, and a roof can make more sense than building an addition.

An attic or basement might need only minor structural modifications and mechanical extensions to make the space habitable. By staying within a home’s envelope, the character and scale of the original house are maintained, and valuable yard space is preserved. A not-so-apparent bonus of converting an attic or basement is the opportunity to improve existing conditions such as insufficient insulation, undersize structural components, and obsolete mechanical systems.

 

STRUCTURAL EVALUATION

Basement

Concrete: If the existing floor shows no evidence of moisture or efflorescence, it can probably be reused. If it’s old, cracked, or not level, or if water is present, replace it. If you have enough ceiling height, a new slab can be poured on top of the old one as long as the subgrade is prepared and waterproofed properly. If the walls are concrete, look for cracks and signs of moisture, especially if the wall is below grade.

Wood: If the floor sags, strengthen it with intermediate joists and midspan blocking. If the walls are wood-framed, ascertain if they have any damage, such as mold, dry rot, or pest infestation, and replace all damaged wood.

Wet basement? If it’s not possible to waterproof the exterior wall, deal with the water inside. Mild moisture problems can be controlled by damp-proofing the walls on the inside by covering them with a layer of rigid foam or closed-cell insulation followed by a pressure-treated stud wall finished with drywall. Heavier flows can be controlled by cutting channels in the floor to direct runoff toward a sump pump.

REMODEL CHECKLIST

Basement

No brainer: The easiest space to convert is a dry basement with an existing floor and walls. As long as it has the minimum ceiling height, the only thing you need to do is evaluate the structural condition of the floors and walls and satisfy code requirements for habitable space.

More complicated: A bit more difficult conversion is creating a basement level from an existing large crawlspace by adding floor framing. This is a popular technique in hilly landscapes. Depending on the steepness of the grade, the new basement floor also might change levels as the grade descends.

Still might be worth it: Raising a house to create a basement level is more expensive, but may be part of a foundation upgrade and drainage improvements. A slab floor adds the least height. A wood floor is easy to insulate, and the crawlspace below is a convenient area to run pipes, ducts, and electrical conduit.

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