According to most building codes, basement and attic stairways must be at least 36” wide, with a mini mum of 6 ft., 8” of headroom. Each step may have a maximum riser height of 7 3/4” and a minimum tread depth of 10”. In addition, stairwells are required to have a 34”- to 38"-high handrail on at least one side, and a minimum 36-deep landing at both the top and bottom of the stairs. and all stairways must be illuminated.
When evaluating your stairway, take into account your finishing plans. Steps must be as uniform as possible, with no more than a 3/8” variance in riser height. Thick tile or a basement subfloor that runs up to the first step will shorten the height of the first riser, creating an unsafe situation that doesn’t meet code. You can adjust a new staircase to compensate for this, but an existing one doesn’t offer such flexibility
To plan a new staircase, consider how it will affect the surrounding spaces, as well as the traffic patterns, on both floors. The type of staircase you choose and where you put it will largely be determined by the available floor space. A standard straight-run stairway will occupy almost 50 sq. ft. of floor space on the lower level and 35 to 40 sq. ft. on the upper level. L- and U-shape stairways make 90° and 180° turns, respectively allow them to fit into smaller areas. Winders are L-shape stairs that make the turn with wedge- shape steps rather than a square platform. These allow a steeper rise in a confined area.
A spiral staircase offers a space-saving alternative for attic access. Spirals are available in stock sizes, or you can have them custom-built. However, spirals aren't for everyone. They can be difficult to use for older people and young children, and some building codes limit their use as primary staircases.