Basic Stairway Arrangements • Stairway Components Unit 63 Types of Stairways Basic Stairway Arrangements • Stairway Components
Interior stairways lead to upper or lower levels within a building. Main or primary stairways serve the inhabited areas of a building. Service stairways serve the uninhabited areas such as a basement or attic. Interior stairways are located inside a building. See Figure 63‑1.
Exterior stairways lead to entrances or decks. Exterior stairways are located outside a building and lead to entrances or decks. See Figure 63‑2.
Stairway arrangements are based on room design. Room design determines the stairway arrangement. Figure 63‑3 shows basic stairway arrangements. The simplest stairway to construct is a straight‑flight (straight‑ run) stairway without a landing. A straight-flight stairway runs in a direct line from one floor to another.
Stairways may be enclosed by walls or railings. Stairways may be enclosed by walls or railings. See Figure 63‑4. If a stairway is enclosed by walls on both sides, handrails are attached to the walls. In another type of stairway, a short wall may form the railing for one or both sides of the stairway. Still another type of stairway has a balustrade on one or both sides. A balustrade is formed by balusters and a handrail. Balusters (banisters) are upright pieces that extend between the handrail and treads.
A stairway is composed of many components A stairway is composed of many components. Main stairways are commonly outfitted with balusters and newel posts. Figure 63‑5 illustrates the components of an interior stairway with a balustrade. An explanation of these components follows: A. Landing newel post: Newel posts are installed at the ends of the stairway and where stairways change direction. The main post supporting the handrail at the landing is the landing newel post. B. Gooseneck: A gooseneck is a curved or bent section at the upper end of a finish handrail. A gooseneck is used to connect the straight section of handrail to a newel post. C. Baluster: The upright pieces that run between the handrail and treads are balusters. D. Handrail: A handrail is grasped by the hand for support when using a stairway. …see complete list of the components of an interior stairway with a balustrade on page 686.
A stringer provides the main support for a stairway A stringer provides the main support for a stairway. Treads and risers are fastened to the stringers. The stringers, or carriage, provide the main support for a stairway. Finish treads and risers are nailed to the stringers. See Figure 63‑6.
Four types of stringers are cleated, dadoed, cut-out, and housed Four types of stringers are cleated, dadoed, cut-out, and housed. Cleated or dadoed stringers are used for stairways to basements and other uninhabited areas of a building. Cut-out or housed stringers are usually used for other stairways. Stringers may be cleated, dadoed, cut-out, or housed. See Figure 63‑7. A cleated stringer is a type of stringer with cleats nailed to it to support the treads. A dadoed stringer is a type of stringer in which treads fit into dadoes cut into the stringer. Cleated and dadoed stringers are typically used for stairways to a basement and other uninhabited areas of a house. However, attractive and modern dadoed stringer designs may be used for main stairways as well.
The total rise of a stairway is its total height and the total run is its length. The unit rise is the riser height and the unit run is the tread depth. The unit rise (riser height) is determined by dividing the total rise of a stairway by the number of risers. See Figure 63‑8. The total rise is the vertical distance of a stairway from the finished floor to the finished floor above.
Preferred angles for stairs fall between 30° and 35°. Stringers should be laid out so that a set of stairs will rise at a safe and comfortable angle. Figure 63‑9 shows preferred versus critical angles. Preferred angles afford the most comfortable walking angles. Critical angles are the minimum and maximum angles for walking safety. The preferred angle for a stairway is 30° to 35°. Critical angles are 20° to 30° and 35° to 50°. For a stairway to rise at a certain angle, the proper combination of tread depth and riser height must be used.
Riser height is calculated first, followed by tread depth calculations Riser height is calculated first, followed by tread depth calculations. In this example, the total rise of the residential stairway is 8′-11″ and the total run is 12′-4 3/4″. Exact tread and riser sizes are based on the total rise and run of a stairway. Figure 63‑10 shows the procedure for calculating tread and riser sizes for a residential stairway with a total rise of 8′‑11″. Total rise is found by adding the rough floor‑to‑ceiling height, actual header width, and subfloor thickness (8′-1″ + 9 1/4″ + 3/4″ = 8′-11″).
Square gauges are positioned on a framing square to ensure accurate tread and riser measurements. In this example for a residential stairway, the risers are 7 1/4″ high and the treads are 10 1/2″ deep. The stairway has seven treads and eight risers. A framing square is used to mark treads and risers on a stringer. Square gauges are positioned on the blade and tongue of the framing square to ensure consistent measurements during layout. The tread depth is indicated on the blade and the riser height is indicated on the tongue. Figure 63‑11 shows a procedure for marking treads and risers on a cut-out stringer with seven 10 1/2″ treads and eight 7 1/4″ risers.
When dropping the stringer, all riser heights will be equal when a finish floor is placed. A small amount of material may need to be deducted from the bottom step so all finished riser heights are equal after the tread material is nailed to the stringer. This calculation is called dropping the stringer. See Figure 63‑12.
Stringers must be securely fastened at the top and bottom since the stringers carry the main load of the stairway. After the stringers are cut to the proper size, they must be fastened in place. Stringers carry the main load of a stairway and must be securely fastened for strength. Figure 63‑13 shows common methods for fastening stair stringers at the top and bottom.