The second type is the closed stringer, sometimes referred to as routed, housed, boxed, solid, or side stringers, whose treads are contained in between the stringers. Some carpenters refer to this type of stringer as a carriage because it exposes the treads and risers. This stringer is cut open with the rise and run measurements. The first type is the cut stringer, sometimes referred to as the open or sawtooth stringer, whose treads are exposed when viewed from the side of the stairway. There are two common types of stringers for stairs in residential buildings. The information presented here covers 2x12-inch board stringers. And the stringers and treads could be made from 5/4-inch- thick boards of pine, poplar, oak, or Douglas fir. Some finish carpenters prefer to remove the entire rough stairway and build a housed-stringer stairway that has treads and risers fitted and glued into routed dadoes of closed, solid stringers.
#Irc stair rail code install
A finish carpenter will later remove the rough treads and install finished treads, risers, and inner and outer skirt boards. Framers will cut stringers from 2x12-inch boards or sometimes laminated veneer lumber (LVL), and then attach rough treads for temporary use during the home's construction. Stairs inside a house are often built by two different contractors. The throat depth is the net depth of a stringer once the steps are cut and removed, and it is measured from the step perpendicular to the bottom edge of the stringer. These tread and riser dimensions directly affect the size of the stringer board, the throat dimensions of a cut stringer, and the amount of board remaining beneath the tread-riser piece that was removed. That is measured horizontally between the vertical planes of the foremost projection of the adjacent treads at a right angle to the tread's leading edge. The tread depth must be at least 10 inches (254 mm). That is measured vertically between the leading edges of the adjacent treads. The primary function of the stringer is to provide a framework and load-bearing support for the treads and risers.Īccording to the 2018 IRC, R311.7.5, the riser height maximum is 7-3/4 inches (196 mm). The stair stringer is a structural member installed on either side or in the center of a flight of stairs into which the treads and risers are attached. Therefore, it's mostly left to the builder's or contractor's knowledge, experience, and the rules-of-thumb they follow in relation to stair stringers. There are limited dimensional constraints for residential interior stair construction.
#Irc stair rail code code
Most of the code provisions describe dimension minimums and maximums for width, rise, run, and vertical height. The International Residential Code (IRC) and the International Building Code (IBC) contain few provisions regarding wood-framed stair stringer design and construction. Stair stringers should meet the general construction standards except where amended by the local jurisdiction. Despite those issues, there are a lot of general rule-of-thumb recommendations but very few specific prescriptive code construction provisions for wood-framed stair stringers in residential buildings. Structural performance issues of stair stringers in residential buildings can result in problems ranging from cracking of the cosmetic finish and vibrations to major structural failures, which can result in severe injuries. The home inspection will not reveal every issue that exists or ever could exist, but only those material defects observed by the inspector on the date of the inspection. A home inspection report shall identify, in written format, defects within specific systems and components defined by the Home Inspection Standards of Practice that are both observed and deemed material by the inspector. The image below is of a cut stringer, a common but a mostly hidden component of an interior finished stairway.ĭuring a home inspection, the stair stringers are usually covered up, and therefore not observed and not inspected. Understanding the components of a stairway, including the stringers, may help a home inspector do a better job. The following information is about a load-bearing component of the stairway that is usually not readily visible and beyond the scope of a visual-only home inspection – the stair stringer. According to the InterNACHI® Home Inspection Standards of Practice ( the home inspector is required to inspect the stairs, steps, landings, and stairways.
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