Stringers support the components of a staircase.David Sacks/Lifesize/Getty Images
Building a set of stairs can be tricky. Every single measurement must be precise, or the stairs may make those who use them stumble or trip. Stairs that are not supported correctly can buckle or collapse, causing injury. Stringers provide a supportive framework on which to anchor the components of the stairs. They are the foundation on which the stairs are built and must be strong enough to support the weight of the people who use them.
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Stair stringers should be made from 2-foot by-12 foot boards. These boards should be at least 5 inches thick to provide enough support. Ninety degree angles are marked on the boards where each stair will be located. The angles are then cut with a circular saw. The tread is attached to the horizontal surface of the angle, while the risers are attached to the vertical surface of the angle. Stringers should be spaced no more than 36 inches apart from each other for maximum stair support, according to the International Association of Certified Home Inspectors. However, local residential codes may vary slightly, so check the building codes before building a staircase.
The treads of a stair are the horizontal pieces that people step on when walking up and down the stairs. There are usually at least three stair stringers supporting the treads; there is one on each end and in the middle of the tread, depending upon the size of the stairs. A set of stairs may need even more stringers if the width of the stairs exceeds 72 inches to ensure that the stringers are no more than 36 inches apart. These stringers should be strong enough so that a person walking on any part of the tread, in the middle or on the sides, will feel no difference in tread stability.
Risers are vertical boards that join two stair treads together. Once mounted on the stair stringers, they act as a type of kickplate, preventing a person's foot from entering the space on the stairs between the treads. They also give the stair additional stability. Some staircases do not use risers so that an open, airy decor is maintained. Support of each tread then falls fully on the stringers. Where risers are used, standard riser height is 7 5/8 inches.
The end stringers on an open staircase may also support the balusters. Balusters, also called spindles, pickets or turnings, are decorative pieces of wood that fit between the stair stringers and a handrail. The balusters and handrail prevent people and objects from falling over the open side of a staircase. According to the International Association of Certified Home Inspectors, stairs with four or more risers should have a handrail on one, if not both, stair sides.