Typically older basements are not built to code to be able to convert your basement area to a liveable dwelling. This is typically because the windows are too small to meet building codes and allow safe exit from the residence in case of an emergency. Likewise, many basements were converted before these codes and requirements were put in place, so your finished basement might not be up to code if it doesn't have egress windows.
Local code regulations vary from county to county and city to city, so it is important to consult your local code administration office about basement window regulations in your area. Most regulations require one egress window in every room that is up to code and allows safe exit from the house. Local housing officials will likely require one egress window for every bedroom-sized room in a basement, whether the room is labelled as a bedroom or not. A small den may require an egress window as well, so mislabelling blueprints is by no means a way to get around these building codes. Although adding egress windows to a basement is a formidable expense, a finished basement with egress windows will make up the cost 15-fold when it comes time to sell your home.
International Residential Codes (IRC) state that all bedroom windows must have one egress window, although local codes may specify otherwise. Bedroom windows must have a 20-inch minimum width of opening, with a minimum height of 24 inches. The minimum net clear opening must be 5.7 square feet, or 5 square feet on ground-floor bedrooms. The maximum height of the sill can be no more than 44 inches; if the window is located under a porch or deck, you must leave an additional 48 inches from bottom of the deck or porch joists to the top of the window.
Basement windows built below the foundation of the house may also require window wells. A window well must provide at least 9 square feet of floor area. The window well must be a minimum of 36 inches in length and width. If the window well exceeds a depth of 44 inches, it must contain steps for climbing or a ladder. Ladders must be 12 inches wide and have to be permanently affixed to the window well. The ladder must project at least three inches from the window well and cannot obstruct the window from opening.