Legal Depth of Stairs

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The width of the staircase refers to the distance from one side to the other as you go up or down the stairs. According to the IRC, this distance must be at least 36 inches and does not include handrails. Based on stair codes and safety research, we recommend designing stairs in such a way as to maximize the depth of stair steps as much as possible. A stair step must be at least 11 inches deep for stairs used as a means of exit under the IBC Building Code 2018. A stair step must be at least 9.5 inches deep for stairs used as an access device according to OSHA standards for stairs. Critical measurements such as standard stair width, climb height, and tread depth are not a matter of guesswork when renovating or building a home. Stairway measurements are determined by current practice and building codes, which in turn are often influenced by generally accepted practices. These rules aim to make stairs as safe as possible, so they should never be ignored or bypassed. There is no maximum tread depth of the staircase according to IBC 2018 stair design criteria or OSHA stair design criteria. There are only minimum requirements for the tread depth of the staircase. IBC 2018 states that “tread depth is measured horizontally between the vertical planes of the most advanced projection of adjacent treads and perpendicular to the leading edge of the tread.” It is a measure of the surface area available to the user`s foot to rest when climbing or descending stairs. The construction rules for the steps are in place for the safety of everyone who can use these stairs. It`s important to remember that consistency may be the most important thing you can get out of it and your inspector will make sure you stick to it.

If all the step and stair measurements for tread depth and climb height are the same, the safety risk is significantly reduced. Stairway code requirements are present for a reason, and for stairs that fall within the mandatory dimensions set by IRC and IBC, the concern about hazard should be eliminated. At the same time, stair code measurements allow for flexibility, as most measurements are accompanied by minimum or maximum values. A great example is the standard stair width. The stair code states that stairs must be 3 feet wide or more. As long as the 3-foot width standard is met, you can extend the width of the stairs as much as you want. (i) Height of climb and tread depth. The maximum climb height shall not exceed 8 1/4 inches and the minimum tread depth shall not be less than 9 inches. The climb height shall be measured vertically between the leading edges of adjacent intrusions.

The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and perpendicular to the leading edge of the tread. The tread of steps and platforms of a staircase shall not be steeper than a vertically inclined unit in 48 units horizontally (an inclination of 2%). The greatest height of climb in a staircase should not exceed the smallest by more than 3/8 of an inch. The maximum tread depth in a staircase should not exceed the smallest by more than 3/8 of an inch. Stair steps should be deep enough so that much of your foot has enough space to rest on the stairs. The walking depth of the stairs is more problematic downhill than uphill. In addition, the measurement of the profile of each tread in a staircase should be as close as possible to the identical. The maximum tread depth inside a staircase shall not be more than 3/8 of an inch greater than the smallest tread depth.

Alternatively, there are also regulations on commercial stairs that must be followed. There are small differences in the size of the stair profile for residential and commercial buildings. The International Building Code establishes the commercial building code for stairs. IBC stair codes are slightly different from those defined by IRC. For example, the maximum stair climb height is 7 inches and the minimum height is 4 inches. The requirements for the stair profile code are also slightly different, with a minimum depth of 11 inches. For both codes, the maximum permissible difference in height and depth is 3/8 of an inch, just like for residential stair code measurements. Another section of the stair specifications of IBC commercial stair codes is that no stair step nose is required as long as the minimum depth is 11 inches. Definition. “Fixed stairs” means internal and external stairs for machinery, tanks and equipment, as well as stairs leading to or from floors, platforms or pits. This term does not apply to stairs intended solely for emergency exits, articulated stairs (whose angle changes with the rise and fall of the base support) or stairs that are an integral part of machinery. This code specification is designed to prevent stairs from being too high when they go up or too low when they go down.

In addition, the pitch measurement of all treads should be as close as possible to the same. The maximum height of climb in a staircase should not exceed the smallest by more than 3/8 of an inch. A staircase in which there is a noticeable variation between risers presents a safety risk. You can see on the board that the minimum tread depth and the maximum climb height vary greatly between different types of stairs. The profile and dimensions of the climb height depend on the standard stair angle. In general, steeper inclined stairs, such as ship stairs or ship ladders, have a smaller profile depth because as the stairs increase, the stairs at the top become an obstacle to the lower step. OSHA 1910.25(e)(2) requires ship stairways to have open risers with a vertical elevation between steps of 6.5 to 12 inches (17 to 30 cm). (3) Continuity. The required handrails must be continuous from a point directly above the forward edge of the lowest stair step to a point directly above the front edge of the landing or the floor surface at the top of the stairs. If the handrail is extended to the top of the stairs, the extension must be parallel to the ground or landing surface and must be at the same height as the handrail above the leading edges of the intrusions. If the handrail is extended at the foot of the stairs, it shall be parallel to the staircase for a tread depth measured horizontally by a step depth before being terminated or retracted or extended horizontally.

The ends of the handrails must return to a wall or end in a security terminal or Newel pole. Tread depth varies greatly between types of stairs. Research shows that sufficient tread depth is an important safety factor for stairs. You can see the difference tread depth makes when descending an alternating profile staircase with a tread depth of 8.5″ compared to a steep staircase with a tread depth of 4″. Stair layout requirements vary slightly between commercial and residential buildings. When you start constructing a new building or renovating an existing structure, it is important to be aware of the various inspection regulations and practices.