Stairways are such an efficient and well-tested method of traversing different levels, that they're common in American homes with multiple floors. They can exist as a few steps connecting a deck with gardens, outdoor spirals joining small spaces or standard inclines between floors. Bulkhead stairways are a less well-known type of residential construction.
A stairway or basement bulkhead is an enclosed construction that connects an exterior level, such as in a yard or driveway, to an underground part of the house, such as a basement or root cellar. The walls, ceiling and staircase of this structure are typically made from concrete or stone. One or two doors usually swing outward from the entrance, to prevent water, animals and other sources of destruction from entering the space. Homeowners can lock the doors to prevent unwanted visitors from breaking into the home. The entire bulkhead and steps are usually known as bulkhead stairways in construction manuals and building codes.
Local, state and some federal jurisdictions specify the standards that residences and their stairways must follow, such as their widths, inclines, tread depths and riser heights. These are based on the International Residential Code, or IRC, developed by the International Code Council. These rules ensure that constructions remain safe and usable to the homeowner, his family and visitors. However, most also specifically exempt bulkhead stairways from following these standards, as long as another exit method is provided for the underground level, the change in levels is 8 feet or less -- and the bulkhead has the required doors.
Stairway bulkheads that do not meet the exceptions need stairways that are at least 36 inches wide at all points, from the stair step up to the required headroom height of 80 inches. The steps or treads must have a minimum depth of 10 inches. Their risers, which form the vertical separations between treads, must be a maximum of 7.75 inches high. Though risers may slope, their angle cannot exceed 30 degrees. Open risers must not allow the passage of a 4-inch-diameter sphere, which is the size of a small child's head.
The Americans with Disabilities Act, or ADA, specifies construction codes based on the IRC that allow use by individuals with handicaps. Because stairway bulkheads that meet exceptions are generally inaccessible to those in wheelchairs or with mobility issues, the ADA does not define special standards for them. It instead relies totally on IRC codes for standards. However, some regulations exist for stairway bulkheads that do not meet the exceptions. These include having a slope not steeper than 1:48, and requiring handrails on both sides of the bulkhead. Standard residential stairs require handrails only for four or more steps, and then typically on only one side of the stair (see Resources section).