Building codes require a basement bedroom has a window for fire escape purposes. At a minimum the bottom of the window must be no more than 44 inches from the floor and that the actual opening be a minimum of 20 inches wide and 24 inches high. Larger is better, not only to make escape easier but also to allow firefighters packing tools and breathing equipment to enter the area quickly.
If you're considering a basement renovation as a way to expand your living space, don't be surprised if your building-codes office has something to say about it, especially if a new bedroom is part of your plan. Without an egress window in case of fire, regulations simply won't allow a basement bedroom. Because this ruling is fairly recent in many parts of the country, most existing basements were not built with egress windows. It's a conundrum that could keep you cramped for space, with all the space you need right under your feet. Thankfully, you needn't be restricted by the basement your house was built with. You can solve the problem by cutting a large opening in a basement wall and adding a window that meets code requirements for egress. You'll find contractors willing to do this work, often for between $2,000 and $3,000, or you might consider doing it yourself. About $500 and two days of work for two people will usually finish the job. While this is clearly a down-and-dirty project, there's nothing particularly complicated about it, and the savings can be substantial.
What will you get for your investment? The added light let in by the new, deep window can eliminate the dark and dank atmosphere so common to earlier basement finishes. The sensory difference can be remarkable. In basements, more than anywhere else, light is a critical design element.
Of course, the primary benefit of a deep window is egress, an easily accessible opening through which you can escape or a firefighter can enter in the event of a basement fire. Basement fires are common, so this is really more than a code issue. And of course, what's good for you will be good for the next owner as well. With an extra legal bedroom, you could recover 10 to 20 times your window installation costs when you eventually sell your home.
Local regulations vary, so you'll need to start with a visit to your codes administration office. With minor variances, here's what you'll find:
To begin, not all basement rooms need a legal egress window, but certainly no basement bedrooms will be allowed without one. If it has occurred to you to call a given room a den before the inspection and a bedroom after, well, let's just say that this isn't a very original idea. Today, any bedroom-sized room with a closet is considered a bedroom, no matter what the blueprint says. As for size requirements, expect to need a window with an opening of 5.7 square feet. Some codes count the glass area, while others measure the area with the window open. In any case, a vertical casement window with six square feet of access is a good choice for a retrofit installation.
The height of the window installation is also important. The bottom of the window opening should be no more than 44 inches off the floor. Outside, an oversize window well is required. It will need to be at least 36 inches wide and extend 36 inches out from the window. The window well height is also limited to 44 inches, as measured from the well floor. If a deep basement forces a deeper window well, most codes will allow a concrete block on the floor of the well to serve as a step, as long as it doesn't interfere with the window's opening.