A finished attic can provide a very welcome addition to living space, but it’s not appropriate for every home—in fact, it can be a very bad decision. Here are the key things to consider when deciding whether to finish your attic, either on your own or with a contractor…

Height and Space

These are factors that many home owners don’t fully anticipate and that could ruin the whole project…

Ceiling height. Building codes typically require a ceiling height of at least seven feet in all or some specified part of a finished attic. What many home owners don’t realize is that a seven-foot ceiling—especially one that slopes down to the floor—will make the space feel much more cramped. Best: Don’t finish your attic unless a large part of the unfinished ceiling is at least eight feet high.

Staircase space. If your attic ­currently is accessed via a ladder and there’s no obvious spot for a staircase, installing stairs might be so expensive and require so much space in the attic and the floor below that the project isn’t worth it. Ask an experienced remodeling contractor for an evaluation and estimate—attic access issues might mean that it’s actually less ­expensive to have an addition put on your house instead.

Warning: Spiral staircases take little space, but home owners are rarely happy with them. For one thing, you cannot move most medium- or large-sized furniture up and down.

Cooling, Floors and Windows

These are challenges that can almost always be overcome, but many people plunge into finishing projects without fully accounting for them…

Cooling is probably a must. Many attics get stiflingly hot in the spring and summer, and your existing cooling system may not be adequate. Recommendation: A “ductless split system” such as the Toshiba/Carrier Residential Series Ductless is an energy-efficient way to cool and heat a finished attic. It typically costs $2,000 to $5,000 installed.

You might have to reinforce the floor. Unfinished attics often have joists sufficient only to hold up the ceiling below, not to support much additional weight above. Consult an experienced remodeling contractor or structural ­engineer about this even if you finish your attic yourself. Expect to pay about $500 for this consulting help.

You’ll probably have to add windows. Windows not only provide natural light and air—some also qualify as emergency exits, and building codes typically require at least two exits from a finished attic. Dormer windows, which protrude upward from sloping roofs, increase ceiling height, too, and therefore make the finished space feel less constricting. ­Expect to pay $3,000 to $5,000 per newly installed dormer…more for long dormers containing multiple windows.