Stair tread depth and also riser height definitions

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

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Understanding the needs can help ensure her stairs room safe and in compliance with OSHA and also IBC.

Stair Tread Depth Definition

The stairs tread depth code is characterized in OSHA sections 1910.21 and 1910.25 and also in IBC thing 10 method of egress.

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

IBC 2018 claims that "tread depth is measured horizontally between the upright planes of the foremost projection of adjacent treads and also at a ideal angle to the tread"s top edge." the is a measure up of the surface obtainable for the user"s foot to remainder as lock ascend or descend the stair.


Stair Riser elevation Definition

The stairway riser height code is additionally defined in OSHA sections 1910.21 and also 1910.25 and in IBC chapter 10 way of egress.

OSHA 1910.21 specifies a stair riser together the upright (vertical) or skinny member that a stair the is located at the ago of a stairway tread or platform and connects close to the front edge of the next greater tread, platform, or landing.

According to IBC 1011.5.2, the riser elevation is measure up vertically in between the nosings (the top edge) of nearby treads.


Minimum stair Tread Depth

OSHA and also IBC have various tread depth needs for various stair types. OSHA introduced minimum tread depth in that 2017 upgrade to walking-working surface ar standards. IBC has forced minimum tread depth for many years.

OSHA and also IBC determine the minimum tread depths and also maximum riser heights based upon research of stairways with various tread and also riser dimensions. One necessary study by man Templer in 1976 confirmed that reduce tread depth to much less than around 11 inches result in an ext missteps. Other studies have presented that together tread depth narrows missteps increase. Based on these results and others, the significant building codes adopted standards because that minimum tread depth and riser heights.

Standard stairway Tread Depth Requirements

Under OSHA, a standard stair method a fixed or permanently set up stairway that is not an alternating tread stair, ship stair, or spiral stair.

OSHA 1910.25(c)(3) requires standard stair to have a minimum tread depth of 9.5 customs (24 cm).

IBC 1011.5.2 needs that stairway treads be 11 inches (279mm) minimum measured horizontally in between the vertical planes the the foremost projection of surrounding treads and at a right angle to the treads top edge.

In team R-3 occupancies, within dwelling devices in R-2 occupancies, and within team U occupancies that are accessory to group R-3 occupancies or accessory to separation, personal, instance dwelling systems within R-2 occupancies, the minimum tread depth shall be 10 inches.

The 10 customs minimum tread depth applies to many permanent residential occupancies with multiple populated units.

Alternating stair Tread Depth Requirements

Alternating tread stairs space a kind of delivery ladder used to accessibility tight spaces. OSHA specifies an Alternating tread-type stair together a form of stairway consisting of a series of treads that usually room attached come a facility support in an alternative manner such the an employee commonly does not have actually both feet on the very same level while using the stairway.

OSHA 1910.25(f)(3) requires alternative tread stair to have a minimum tread depth the 8.5 inches (22 cm).

IBC 1011.14.2 requires alternate tread tools to have actually a minimum projected tread depth that 8.5 customs (216mm).

Ships Ladder Tread Depth Requirements

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

OSHA 1910.25(e)(3) calls for ship stair to have actually minimum tread depth the 4 inch (10 cm).

IBC 1011.15.2 calls for ships ladders to have actually a minimum tread depth of 5 inch (127mm).

Spiral stair Tread Depth Requirements

OSHA specifies a Spiral stair as a collection of treads attached come a vertical pole in a winding fashion, normally within a cylindrical space.

OSHA 1910.25(d)(4) requires spiral stairs to have actually a minimum tread depth the 7.5 inches (19 cm), measured at a point 12 inches (30 cm) from the narrow edge.

IBC 1011.10 requires spiral stairways to have actually a 6 3/4 customs (171mm) minimum clean tread depth in ~ a allude 12 customs (305mm) native the small edge.

Minimum stairs Tread Depth Chart


Standard stairs



Alternating tread stairs



Spiral stairs



Ship stairs



Tread depths vary considerably between stair types. Research reflects that having actually adequate tread depth is a major safety element of stairways. You deserve to see the difference tread depth makes as soon as descending an alternating tread stair v 8.5" tread depth compared to a steep stair v 4" tread depth.

Maximum stairway Riser Height

OSHA and also IBC additionally have various maximum stairway riser height requirements depending upon the kind of stairway.

Standard stair Riser elevation Requirements

OSHA 1910.25(c)(2) requires standard stairs to have actually a preferably riser elevation of 9.5 inches (24 cm).

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

In team R-3 occupancies, in ~ dwelling units in R-2 occupancies, and also within team U occupancies that are accessory to team R-3 occupancies or accessory to separation, personal, instance dwelling systems within R-2 occupancies, the maximum riser height shall be 7-3/4 inches.

The 7-3/4 customs maximum riser uses to most permanent residential occupancies with multiple populated units.

Alternating stairway Riser height Requirements

OSHA does no state especially a best riser height for alternative tread stairs. Because that treads and also riser of alternative tread stairs, OSHA calls for that alternative tread stairs have a collection of treads set up at a steep of 50 come 70 levels from the horizontal and also that they have actually a minimum tread depth of 8.5 inch (22 cm). If tread depth is less than 9.5" alternate tread stairway must have actually open riser.

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

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Spiral stairway Riser elevation Requirements

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

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

Ships Ladder Riser elevation Requirements

OSHA 1910.25(e)(2) needs ship stairs to have actually open risers with a vertical rise between tread surface of 6.5 come 12 customs (17 to 30 cm).

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

Maximum stairs Riser elevation Chart


Standard stairs



Alternating tread stairs



Spiral stairs



Ship stairs




You can see indigenous the chart the the minimum tread depth and maximum riser heights vary greatly in between different stairway types. The tread and riser elevation dimensions depend on the traditional stair angle. Generally, steeper angled stairs, choose ship stair or ships ladders, have less tread depth because as a stair gets steeper, the tread over becomes an obstacle to the tread below.


OSHA introduced it"s very own minimums because that tread depth and riser height in the 2017 update to walking-working surfaces.

Based top top the stairway codes and safety research, we recommend making stairs to maximize stairs tread depth as lot as possible.

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

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

FAQs ~ above Stair Riser elevation & stairs Tread Depth Codes

What is the conventional stair tread and riser?

The typical stair tread is the horizontal member that a stair that serves as the wade surface. The typical riser is the upright member of a stair that is situated at the ago of a stairway tread and connects close come the front leaf of the next greater tread.

Is there a preferably stair tread depth?

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

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How deep have to a stairway tread be?

A stairs tread need to be a minimum the 11" deep because that stairs supplied as a means of egress under the 2018 IBC structure code. A stairs tread need to be a minimum 9.5" deep because that stairs provided as equipment accessibility under the OSHA requirements for stairways.

What is password for rise and run of stairs?

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