Stair tread depth, stair riser height, minimum stair tread depth requirements and maximum stair riser height requirements are defined by OSHA and IBC. Understanding the requirements can help ensure your stairs are safe and in compliance with OSHA and IBC. The stair tread depth code is defined in OSHA sections 1910.21 and 1910.25 and in IBC chapter 10 means of egress. Under OSHA 1910.21 the stair treadmeans a horizontal member of a stair or stairway, but does not include landings or platforms. IBC 2018 states that "tread depth is measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge." It is a measure of the surface available for the user's foot to rest as they ascend or descend the stair. The stair riser height code is also defined in OSHA sections 1910.21 and 1910.25 and in IBC chapter 10 means of egress. OSHA 1910.21 defines a stair riser as the upright (vertical) or inclined member of a stair that is located at the back of a stair tread or platform and connects close to the front edge of the next higher tread, platform, or landing. According to IBC 1011.5.2, the riser height is measured vertically between the nosings (the leading edge) of adjacent treads. OSHA and IBC have different tread depth requirements for different stair types. OSHA introduced minimum tread depths in its 2017 update to walking-working surface standards. IBC has required minimum tread depth for many years.Stair tread depth and riser height definitions
Stair Tread Depth Definition
Stair Riser Height Definition
Minimum Stair Tread Depth
OSHA and IBC determine the minimum tread depths and maximum riser heights based on research of stairways with various tread and riser dimensions. One important study by John Templer in 1976 showed that reducing tread depth to less than about 11 inches resulted in more missteps. Other studies have shown that as tread depth narrows missteps increase. Based on these results and others, the major building codes adopted standards for minimum tread depth and riser heights.
Standard Stair Tread Depth Requirements
Under OSHA, a standard stair means a fixed or permanently installed stairway that is not an alternating tread stair, ship stair, or spiral stair.
OSHA 1910.25(c)(3) requires standard stairs to have a minimum tread depth of 9.5 inches (24 cm).
IBC 1011.5.2 requires that stair treads be 11 inches (279mm) minimum measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the treads leading edge.
In group R-3 occupancies, within dwelling units in R-2 occupancies, and within group U occupancies that are accessory to group R-3 occupancies or accessory to individual dwelling units within R-2 occupancies, the minimum tread depth shall be 10 inches.
The 10 inch minimum tread depth applies to most permanent residential occupancies with multiple dwelling units.
Alternating Stair Tread Depth Requirements
Alternating tread stairs are a type of ship ladder used to access tight spaces. OSHA defines an Alternating tread-type stair as a type of stairway consisting of a series of treads that usually are attached to a center support in an alternating manner such that an employee typically does not have both feet on the same level while using the stairway.
OSHA 1910.25(f)(3) requires alternating tread stairs to have a minimum tread depth of 8.5 inches (22 cm).
IBC 1011.14.2 requires alternating tread devices to have a minimum projected tread depth of 8.5 inches (216mm).
Ships Ladder Tread Depth Requirements
Ship stairs are very steep stairs used to access tight spaces. OSHA defines a Ship stair (ship ladder) as a stairway that is equipped with treads, stair rails, and open risers, and has a slope that is between 50 and 70 degrees from the horizontal.
OSHA 1910.25(e)(3) requires ship stairs to have minimum tread depth of 4 inches (10 cm).
IBC 1011.15.2 requires ships ladders to have a minimum tread depth of 5 inches (127mm).
Spiral Stair Tread Depth Requirements
OSHA defines a Spiral stair as a series of treads attached to a vertical pole in a winding fashion, usually within a cylindrical space.
OSHA 1910.25(d)(4) requires spiral stairs to have a minimum tread depth of 7.5 inches (19 cm), measured at a point 12 inches (30 cm) from the narrower edge.
IBC 1011.10 requires spiral stairways to have a 6 3/4 inch (171mm) minimum clear tread depth at a point 12 inches (305mm) from the narrow edge.
Minimum Stair Tread Depth Chart
 |  | |
Standard stairs | 9.5" | 11" |
Alternating tread stairs | 8.5" | 8.5" |
Spiral stairs | 7.5" | 6.75" |
Ship stairs | 4" | 5" |
Tread depths vary considerably between stair types. Research shows that having adequate tread depth is a major safety factor of stairways. You can see the difference tread depth makes when descending an alternating tread stair with 8.5" tread depth compared to a steep stair with 4" tread depth.
Maximum Stair Riser Height
OSHA and IBC also have different maximum stair riser height requirements depending on the type of stairway.
Standard Stair Riser Height Requirements
OSHA 1910.25(c)(2) requires standard stairs to have a maximum riser height of 9.5 inches (24 cm).
IBC 1011.5.2 requires that stair riser heights shall be 7 inches (178 mm) maximum and 4 inches (102 mm) minimum.
In group R-3 occupancies, within dwelling units in R-2 occupancies, and within group U occupancies that are accessory to group R-3 occupancies or accessory to individual dwelling units within R-2 occupancies, the maximum riser height shall be 7-3/4 inches.
The 7-3/4 inch maximum riser applies to most permanent residential occupancies with multiple dwelling units.
Alternating Stair Riser Height Requirements
OSHA does not state specifically a maximum riser height for alternating tread stairs. For treads and riser of alternating tread stairs, OSHA requires that alternating tread stairs have a series of treads installed at a slope of 50 to 70 degrees from the horizontal and that they have a minimum tread depth of 8.5 inches (22 cm). If tread depth is less than 9.5" alternating tread stairs must have open riser.
IBC 1011.14.2 requires that alternating tread devices have a maximum riser height of 9 1/2" (241mm).
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Spiral Stair Riser Height Requirements
OSHA 1910.25(d)(2) requires spiral stairs to have have a maximum riser height of 9.5 inches (24 cm).
IBC 1011.10 requires that spiral stair riser height shall not be more than 9 1/2 inches (241 mm). The risers shall be sufficient to provide a headroom clearance of 78 inches (1981mm) minimum.
Ships Ladder Riser Height Requirements
OSHA 1910.25(e)(2) requires ship stairs to have open risers with a vertical rise between tread surfaces of 6.5 to 12 inches (17 to 30 cm).
IBC 1011.15.2 requires ships ladders to have a maximum riser height of 9 1/2" (241mm).
Maximum Stair Riser Height Chart
| | |
Standard stairs | 9.5" | 7" |
Alternating tread stairs | NA | 9.5" |
Spiral stairs | 9.5" | 9.5" |
Ship stairs | 12" | 9.5" |
Conclusion
You can see from the chart that the minimum tread depth and maximum riser heights vary greatly between different stair types. The tread and riser height dimensions depend on the standard stair angle. Generally, steeper angled stairs, like ship stairs or ships ladders, have less tread depth because as a stair gets steeper, the tread above becomes an obstacle to the tread below.
OSHA introduced it's own minimums for tread depth and riser height in the 2017 update to walking-working surfaces.
Based on the stair codes and safety research, we recommend designing stairs to maximize stair tread depth as much as possible.
For applications without space-restrictions, choose standard stairs with as close as possible to 11" tread depth.
For space-restricted applications, choose alternating tread stairs with more than 2x the usable tread depth as ships stairs.
FAQs On Stair Riser Height & Stair Tread Depth Codes
What is the standard stair tread and riser?
The standard stair tread is the horizontal member of a stair that serves as the walking surface. The standard riser is the vertical member of a stair that is located at the back of a stair tread and connects close to the front edge of the next higher tread.
Is there a maximum stair tread depth?
There is not a maximum stair tread depth under either the 2018 IBC stairway design criteria or the OSHA stairway design criteria. There are only minimum stair tread depth requirements.
How deep should a stair tread be?
A stair tread should be a minimum of 11" deep for stairs used as a means of egress under the 2018 IBC building code. A stair tread should be a minimum 9.5" deep for stairs used as equipment access under the OSHA standards for stairways.
What is code for rise and run of stairs?
The 2018 IBC building code for rise and run of stairs is a maximum 7" rise and minimum 11" run (tread depth). The OSHA standard for rise and run of stairs is maximum 9.5" rise and minimum 9.5" run (tread depth). The IBC maximum rise of a single stair flight is 12.'
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FAQs
What is the minimum tread depth and riser height? ›
The OSHA standard for rise and run of stairs is maximum 9.5" rise and minimum 9.5" run (tread depth).
What is code for the depth of a stair tread? ›International Residential Code (IRC)
There are also section codes in place for standard stair tread dimensions. The tread depth code for residential stairs should be no less than 10 inches with nosing, no less than 11 inches without nosing, and maximum tread depth variation should also be less than 3/8 of an inch.
(1) The rise of every step in a stairway shall be not less than 4 inches nor greater than 7 1/2 inches. (2) The run shall not be less than 10 inches as measured horizontally between the vertical planes of the furthermost projection of adjacent treads.
What is the maximum height of riser should be? ›For indoor stairs, the riser should be between 0.12 m and 0.18 m, and the tread between 0.28 m and 0.35 m. For outdoor stairs, the maximum riser should be 0.15 m and the minimum tread should be 0.30 m.
What is the legal requirement for tread depth? ›Minimum legal tread depth
So, what is the minimum tread depth required for car tyres? While a new car tyre begins life with approximately 8mm of tread, the minimum legal tread depth is 1.6mm. However, most motoring organisations recommend changing your tyres before the tread gets to this level.
Most states require a minimum of 2/32 of an inch (approximately 1.6 mm) of tread, but two require less, some have no requirements, and some defer to the federal criterion for commercial vehicle safety inspections.
What is the maximum riser for stairs? ›The vertical distance between the two adjacent treads is known as riser height. The height of the riser prescribed as per the codes is not more than 7 ¾ inches in height.
What is the standard stair riser height? ›Staircase standards
With regard to the standard height of a staircase riser, the measurement is often between 6-1/4 and 7-7/8 inches. With respect to the step run, this measurement is between 8-1/4 and 12-1/2 inches.
The maximum height of the riser that is provided in the staircase should be between 150 mm to 200 mm.
What is the maximum tolerance in riser height and tread depth of stairs? ›Stair treads and risers shall be of uniform size and shape. The tolerance between the largest and smallest riser height or between the largest and smallest tread depth shall not exceed 3/8 inch (9.5 mm) in any flight of stairs.
Is an 8 inch step too high? ›
In the United States, the step height standard should be between 7 or 7 ¾ inches at the most, and no less than 4 inches. You should follow other measurements if given by local building codes. In Canada, the maximum step riser height is 8 ¼ inches.
What are ADA requirements for stairs? ›Stair treads shall be no less than 11 in (280 mm) wide, measured from riser to riser. Open risers are not permitted. Each stair tread is 11 inches (280 mm) deep minimum with a sloped riser. The nosing shall project no more than 1-1/2 inches (38 mm).
What is the ideal tread to riser ratio? ›An “ideal” ratio is 7 in. rise and 10 in. tread. These dimensions may vary slightly if the rise and/or run of a stairway must be held within certain limits.
What is the relation between tread and riser? ›Tread: It is an upper horizontal portion of a step upon which foot is placed while ascending or descending. Riser: It is a vertical portion of a step providing support to the tread.
What is unsafe tread depth? ›A tire with a tread depth below 1.6 millimeters (2/32 inches) lacks grip. Braking distance and vehicle control are impaired. These tires are not safe for driving and must be replaced.
What depth is 7 32 tread? ›| Fraction /32"s | Inch | MM |
|---|---|---|
| 7/32" | 0.219 | 5.56 |
| 8/32" | 0.250 | 6.35 |
| 9/32" | 0.281 | 7.14 |
| 10/32" | 0.313 | 7.94 |
The legal minimum tread depth for cars is 1.6 millimeters. This 1.6 mm should be in a continuous band throughout the central three-quarters of the tread width, throughout the whole of the circumference.
Is 4 32nds of tread depth legal? ›According to Federal Motor Carrier Safety Administration (FMCSA) regulations, the minimum tread depth for a steer tire is 4/32 of an inch on every major tread groove. If one spot on one groove is less than 4/32, then a driver will be issued a citation.
What is the minimum and maximum riser height? ›The riser's height must fall between 0.6 and 0.7 feet.
What are the step height requirements for OSHA? ›Riser height shall be from 6 to 7.5 inches (15.24 to 19.05 cm), stair width a minimum of 22 inches (55.88 cm) between vertical barriers, tread depth a minimum of 12±2 inches (30.48±5.08 cm), and tread nosing shall be straight leading edges. Stair landings shall be at least 20 inches (50.8 cm) in depth.
What is the average step height and depth? ›
The average step height in America is 7.5 inches. The depth is generally around 9 inches. As far as width goes, or the long part of the stairs, it's primarily up to the homeowner. What is this?
Can a stair tread be 9 inches? ›Most stair treads measure between 8 and 10 inches long, with longer treads being used on larger staircases. Nine-inch stair treads are the most common lengths. To determine the length you need, simply measure from the back of the step to the front of the step.
Can stairs have an 8 inch rise? ›On a main stair, the maximum rise should be no more than 8 1/4 inches and the minimum run should be no less than 9 inches. To determine how many steps, or treads, you need, measure from the top of the finished floor on the lower level to the top of the finished floor on the upper level.
Is a 12 inch step too high? ›The general rule (in the US) is 7-11 (a 7 inch rise and 11 inch run) (17.78cm-27.94cm). More exactly, no more than 7 3/4 inches (19.7cm) for the riser (vertical) and a minimum of 10 inches (25.4cm) for the tread (horizontal or step).
What are the OSHA requirements for stairs? ›Riser height shall be from 6 to 7.5 inches (15.24 to 19.05 cm), stair width a minimum of 22 inches (55.88 cm) between vertical barriers, tread depth a minimum of 12±2 inches (30.48±5.08 cm), and tread nosing shall be straight leading edges. Stair landings shall be at least 20 inches (50.8 cm) in depth.
What is the minimum riser on stairs? ›Stair riser: Vertical measurement from the top of one step to above the next step. It's often between 5 and 8 inches and 7-3/4 inches on average.
What is normal stair riser height? ›Riser Heights
In the United States, the step height standard should be between 7 or 7 ¾ inches at the most, and no less than 4 inches.
Staircase Riser Height: 7 3/4 Inches, Maximum
A stair riser is the back, vertical part of a step. Staircase riser height translates to the distance you move your foot either up or down from one step to an adjacent step. This should be no more than 7 3/4 inches.
From the top flight of stairs to the bottom of the stairs, each individual riser cannot exceed a difference of 3/8 of an inch.