Stair tread depth and riser height definitions

Stair tread depth, stair riser height, minimum stairs tread depth requirements and also maximum stair riser height requirements are defined by OSHA and also IBC.

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Understanding the needs can assist ensure your stairs room safe and in compliance v OSHA and also IBC.

Stair Tread Depth Definition

The stair tread depth password is defined in OSHA part 1910.21 and also 1910.25 and also in IBC thing 10 means of egress.

Under OSHA 1910.21 the stairs treadmeans a horizontal member of a stairway or stairway, but does not include landings or platforms.

IBC 2018 says that "tread depth is measured horizontally between the upright planes of the foremost estimate of adjacent treads and at a appropriate angle to the tread"s leading edge." it is a measure up of the surface available for the user"s foot to remainder as they ascend or descend the stair.

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Stair Riser elevation Definition

The stair riser height code is also defined in OSHA part 1910.21 and also 1910.25 and also in IBC chapter 10 method of egress.

OSHA 1910.21 defines a stair riser as the upright (vertical) or skinny member the a stair that is located at the ago of a stairway tread or platform and also connects close come the front leaf of the next greater tread, platform, or landing.

According come IBC 1011.5.2, the riser elevation is measured vertically in between the nosings (the leading edge) of surrounding treads.

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Minimum stairway Tread Depth

OSHA and also IBC have various tread depth demands for various stair types. OSHA presented minimum tread depth in its 2017 upgrade to walking-working surface ar standards. IBC has required minimum tread depth for plenty of years.

OSHA and also IBC identify the minimum tread depths and maximum riser heights based on research of stairways with various tread and riser dimensions. One necessary study by man Templer in 1976 verified that reducing tread depth to much less than about 11 inches resulted in an ext missteps. Various other studies have displayed that together tread depth narrows missteps increase. Based on these results and others, the major building codes adopted standards because that minimum tread depth and riser heights.

Standard stairway Tread Depth Requirements

Under OSHA, a standard stair means a resolved or permanently installed stairway the is no an alternative tread stair, delivery stair, or spiral stair.

OSHA 1910.25(c)(3) calls for standard stair to have actually a minimum tread depth that 9.5 inch (24 cm).

IBC 1011.5.2 requires that stair treads be 11 inch (279mm) minimum measured horizontally in between the upright planes that the foremost estimate of surrounding treads and at a right angle to the treads leading edge.

In team R-3 occupancies, in ~ dwelling systems in R-2 occupancies, and within group U occupancies that space accessory to group R-3 occupancies or accessory to individual dwelling units within R-2 occupancies, the minimum tread depth shall it is in 10 inches.

The 10 inch minimum tread depth uses to most permanent residential occupancies v multiple dwelling units.

Alternating stair Tread Depth Requirements

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Alternating tread stairs room a type of delivery ladder used to accessibility tight spaces. OSHA specifies an Alternating tread-type stair together a form of stairway consist of of a series of treads that usually room attached to a facility support in an alternate manner such the an employee frequently does not have both feet top top the exact same level while making use of the stairway.

OSHA 1910.25(f)(3) requires alternative tread stairway to have actually a minimum tread depth of 8.5 inches (22 cm).

IBC 1011.14.2 requires alternative tread devices to have actually a minimum projected tread depth the 8.5 inches (216mm).

Ships Ladder Tread Depth Requirements

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Ship stairway are really steep stairs provided to accessibility tight spaces. OSHA specifies a Ship stair (ship ladder) as a stairway that is equipped through treads, stair rails, and open risers, and has a slope the is in between 50 and also 70 degrees from the horizontal.

OSHA 1910.25(e)(3) requires ship stair to have actually minimum tread depth that 4 inches (10 cm).

IBC 1011.15.2 needs ships ladders to have actually a minimum tread depth of 5 customs (127mm).

Spiral stair Tread Depth Requirements

OSHA defines a Spiral stairway as a series of treads attached come a upright pole in a winding fashion, typically within a cylindrical space.

OSHA 1910.25(d)(4) requires spiral stairway to have actually a minimum tread depth of 7.5 customs (19 cm), measured at a suggest 12 customs (30 cm) indigenous the narrower edge.

IBC 1011.10 needs spiral stairways to have actually a 6 3/4 inch (171mm) minimum clean tread depth at a allude 12 inch (305mm) from the narrow edge.

Minimum stairway Tread Depth Chart


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Standard stairs

9.5"

11"

Alternating tread stairs

8.5"

8.5"

Spiral stairs

7.5"

6.75"

Ship stairs

4"

5"


Tread depths differ considerably in between stair types. Research mirrors that having actually adequate tread depth is a significant safety variable of stairways. You deserve to see the distinction tread depth makes as soon as descending an alternative tread stair v 8.5" tread depth contrasted to a steep stair v 4" tread depth.


Maximum stairway Riser Height

OSHA and also IBC likewise have different maximum stairway riser height requirements depending on the form of stairway.

Standard stairs Riser height Requirements

OSHA 1910.25(c)(2) requires standard stairs to have a preferably riser height of 9.5 customs (24 cm).

IBC 1011.5.2 requires that stairs riser heights shall be 7 customs (178 mm) maximum and also 4 inches (102 mm) minimum.

In team R-3 occupancies, within dwelling units in R-2 occupancies, and within team U occupancies that space accessory to team R-3 occupancies or accessory to individual dwelling devices within R-2 occupancies, the preferably riser elevation shall it is in 7-3/4 inches.

The 7-3/4 inch maximum riser applies to most permanent residential occupancies through multiple populated units.

Alternating stairs Riser height Requirements

OSHA does not state specifically a best riser elevation for alternating tread stairs. For treads and riser of alternative tread stairs, OSHA calls for that alternate tread stairs have a series of treads mounted at a steep of 50 come 70 levels from the horizontal and that they have a minimum tread depth that 8.5 inches (22 cm). If tread depth is much less than 9.5" alternative tread stairway must have open riser.

IBC 1011.14.2 calls for that alternating tread tools have a best riser elevation of 9 1/2" (241mm).


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Spiral stairs Riser height Requirements

OSHA 1910.25(d)(2) calls for spiral stairs to have actually have a preferably riser height of 9.5 customs (24 cm).

IBC 1011.10 requires that spiral stairs riser elevation shall no be much more than 9 1/2 inch (241 mm). The risers shall be adequate to provide a headroom clearance the 78 inch (1981mm) minimum.

Ships Ladder Riser height Requirements

OSHA 1910.25(e)(2) requires ship stairway to have actually open risers with a upright rise in between tread surface of 6.5 come 12 customs (17 to 30 cm).

IBC 1011.15.2 requires ships ladders to have a preferably riser height of 9 1/2" (241mm).

Maximum stairs Riser elevation Chart


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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 also maximum riser heights vary greatly in between different stairs types. The tread and riser height dimensions count on the conventional stair angle. Generally, steeper angled stairs, favor ship stair or pearl ladders, have actually less tread depth because as a stair it s okay steeper, the tread over becomes an problem to the tread below.

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OSHA presented it"s very own minimums for tread depth and also riser height in the 2017 upgrade to walking-working surfaces.

Based ~ above the stairs codes and also safety research, us recommend designing stairs to maximize stair tread depth as lot as possible.

For applications without space-restrictions, pick standard stairs v as nearby as feasible to 11" tread depth.

For space-restricted applications, choose alternating tread stair with much more than 2x the usable tread depth together ships stairs.

FAQs ~ above Stair Riser elevation & stairway Tread Depth Codes

What is the standard stair tread and also riser?

The conventional stair tread is the horizontal member the a stair that serves as the walking surface. The standard riser is the upright member that a stair that is located at the earlier of a stair tread and connects close come the front edge of the next greater tread.

Is over there a maximum stair tread depth?

There is no a best stair tread depth under either the 2018 IBC stairway architecture criteria or the OSHA stairway design criteria. Over there are only minimum stairway tread depth requirements.

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How deep must a stair tread be?

A stair tread must be a minimum that 11" deep because that stairs supplied as a means of egress under the 2018 IBC structure code. A stairs tread must be a minimum 9.5" deep because that stairs provided as equipment access under the OSHA criter for stairways.

What is code for rise and also run of stairs?

The 2018 IBC structure code because that rise and also run that stairs is a best 7" rise and minimum 11" operation (tread depth). The OSHA conventional for rise and also run of stairs is maximum 9.5" rise and also minimum 9.5" operation (tread depth). The IBC maximum increase of a solitary stair trip is 12."