Open vs closed stair treads (C) InspectAPedia & Carson Dunlop Associates Stair Dimensions & Clearances for Stair Construction & Inspection
What are the required height, width, slope for stairs?

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Stairway dimensions, recommendations & building code citations:

Stair, railing, guardrail, landing, tread, and step specifications & measurement dimension requirements . Stair & railing sizes, widths, heights, clearances, gaps, measurements - Sketches of stair design measurements & requirements.

This document provides the stair dimensions required by building code specifications and includes sketches, photographs, and examples of defects used in inspecting indoor or outdoor stairs, railings, landings, treads, and related conditions for safety and proper construction.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Summary of Stairway, Railing & Landing Construction Dimensions, Codes, Standards & Rules

Stairway requirements (C) Carson Dunlop AssociatesStairway dimensions & construction requirements & codes are summarized here.

For a complete list of articles on stairs, railings, and ramps, their inspection, trip hazards, and good design,
see STAIRS, RAILINGS, LANDINGS, RAMPS - INSPECTIONS, CODES. Or see these detailed articles on specifications for proper dimensions for stairs, railings, platforms

Because more people are injured by trips and falls than other hazards, experts have looked closely at the specifications for stairs, steps, and rails to reduce the falling hazards.

This work has been translated into stair and railing specifications that are similar among codes and countries (but not identical). -- IBC, IRC, BOCA, Kingston NY Stair Code, & other sources.

Stair and Railing Specification Topics for stair (U.S. and International Residential Codes) include the items listed below.

Stair Dimensions for Straight Stairway Runs: Stair width, landing length

Stairwell width and stair landing platform requirements are summarized by these sketches courtesy Carson Dunlop Associates.

The minimum recommended stair width is between 34" and 36" Across the width of the tread. Some codes such as CA/OSHA specify a minimum stairway width of 24" [35]..

The minimum recommended stair landing length is 36" (or a length and width sufficiently greater than the swing of the door if a wider door is present.

Is a landing required at the top of stairs?

Ordinarily, yes, a top landing is required. For example most exterior stairs approaching a building entry door encounter a door or storm/screen door that swings out. We need somewhere to stand when opening the door.

But a stair top landing is not required if the the stairs rise to a doorway at which the door opens away from the stairwell.

Of course standing one step "down" from the door opening might place the door knob a bit high for shorter users of the entry.

Stairway Height, Width, Headroom Requirements

Stairway width, height, and headroom at an interior passage (C) Daniel Friedman 2012



Exceptions to stair dimension requirements may be made for stairs giving access to non-living areas of a building such as storage lofts and mechanical rooms. Check with your local building officials.

Specifications for Recommended Minimum Stairway Widths & Stair Lengths

  1. Stairway width should be equal to or greater than 36" of clear unobstructed distance measured at all points above the [permitted] hand-railing height. This is the blue arrow in our photograph below.
  2. Stairway width should also be equal to or greater than 36" of clear unobstructed space between the top of the handrail (the permitted handrailing height) and the required headroom clearance upper height.
  3. For a stairway with a railing on just one side, stairway width can be a bit smaller, with a clear width of 31.5" in the space below the handrail height.

    This allows taking into account stair stringer trim such as shown in our photographs. This space is shown with the green arrow in our photograph below.
  4. For a stairway with a handrailing along both sides, the clear stairway width is permitted to be smaller still, with a clear width of 27".
  5. Handrailings should not project more than 4 1/2" into the stairway walking space on either side of the stairway.

Definition of Stairway Width or Stair Width - don't confuse stair width with stair depth

Stairway and stair tread width (C) Daniel Friedman

Watch out: it's confusing but many people refer to stair tread depth see STAIR TREAD DIMENSIONS

also STAIR RISER SPECIFICATIONS ) as stair step or tread width, including our Canadian stair dimension illustration just below.

If you stick to using the word stair tread depth you can avoid this confusion.

Oops, that is, unless you start confusing tread depth with stair tread riser height. Stair tread depth is defined above as the horizontal distance from nose to nose or from riser face to nose on open riser stairs.

Stairway width is the horizontal width of the stair opening (blue arrow in our photo). For stairs enclosed by a wall on both sides, usually the stairway width is the distance between those walls.

Stair tread width (green arrow in our photo) is the horizontal left to right width of the stair tread.

At left our photo illustrates three different stair width measurements

  1. Stair tread width (green arrow) (smaller than stairway width due to side trim boards)
  2. Stairway width (blue arrow) over most of this stairway (nominally 36" or wider)
  3. Stairway width near stair top (pink arrow) due to a wall projection (nominally 36" or wider)
Stairway width measurement (C) D Friedman Eric Galow

Recommended Stairway Width

Stairwell width and stair landing platform requirements are summarized by the sketch above. The measurement locations for determining a stairway width are illustrated in our photo at left, courtesy Galow Homes.

In the stairway shown, the owners opted for a 36" wide stairwell.

The minimum recommended stair width is between 34" and 36" across.

Handrailings reduce the nominal stairwell width

In these sketches and in our photographs used here, the required handrails have been omitted for clarity.

Handrailings will protrude into and may reduce the nominal the stairwell width.

For a 36" wide stairwell such as that shown above, the stair railing intrusion is not a problem, but for more narrow stairs it may be, especially where accessible stairways are required.

Handrail Requirements for Wide Stairways

Center handrail on wide stairs, Carnagie Hall, New York City (C) Daniel Friedman

One use of extra-wide stairways is to permit two-way traffic without people punching into one another going up and down the stairs, while at the same time the stairway may also serve large crowds moving usually in one direction at a time.

The divided stairway shown above is at Carnegie Hall in New York City.

The wide stair requires a center handrailing, typically leaving 36" on either side of the center handrail.

Step Riser Height Specifications & Common Stair Construction Mistakes

Unsafe exterior stair stringer and riser height (C) Daniel FriedmanStair Step Risers

Stair Riser Defects

Details are


Bad Deck Stair Example: Nothing is right about the exterior stairs shown in our photo from a 1991 home inspection:

Open vs closed stair treads (C) InspectAPedia & Carson Dunlop Associates

Closed stair treads using a solid riser are shown at the left of the sketch and

Open stair treads are shown at the right sketch. "Open stair treads" means that no solid riser is installed between the stair treads.

Stair tread nose projection and radius: stair treads should have a projecting nose that is rounded and projecting a maximum of 1.5 " over the tread below.

The requirements for a projecting stair nose over the tread below may be amended for open riser stairs in some jurisdictions, but in no case should the front of a stair tread be more than 1.5" back from the inside edge of the tread below - see sketch annotations. [Click any of our images to see an enlarged, detailed version]

Stair tread thickness: The minimum tread thickness for stair treads supported by risers is 1".

Notice that the minimum stair tread thickness is increased to 1.5" when the stair tread is not supported by a solid riser.

Sketch at above left courtesy Carson Dunlop Associates.

See BALUSTERS, STAIR & RAILING for full details of this topic.

For more details about balusters (vertical spindles in railing construction) see details

at RAILING CODES & SPECIFICATIONS for a discussion of safety barriers along stairs,

see GUARDRAILS on BALCONIES, DECKS, LANDINGS (railings on landings and open hallways, porches, screened porches, balconies that are more than 30" above floors or grade).

Example Building Code Specifications For Stairway Dimensions

California and other U.S. states often take as a starting point for state building codes pertaining to stair, landing, railing, tread and other stairway design specifications the national model building codes. The California CA/OSHA Section 1003.3.3 Stairways and Landings provisions, as well as the California Building Code (CBC) illustrate:

CA/OSHA: California Stair & Railing Code details

The following stair dimension example citation is from CA/OSHA Subchapter 4. General Industry Safety Orders, Article 17. Ramps, Runways, Stairwells, and Stairs. Note: this code establishes minimum occupational safety & health standards that apply to all places of employment in California.

This is not a residential building code requirement, but this text in our OPINION models stair construction safety & design specifications.

See RAILING CODES & SPECIFICATIONS for model building code specifications of when a handrailing is required, heights, stairway widths, graspability, etc.



CA/OSHA Section 1626. Stairwells and Stairs.

CA/OSHA Title 8 Section 1626. Stairwells and Stairs [36] With added stair details quoting from the CBC 1003.3.3

(a) General. [Stairway width, free space, step rise, step run or depth, tread width & riser height variation permitted]

(1) Stairways shall be al least 24 inches in width and shall be equipped with stair rails, handrails, treads, and landings.

Note: this is a CA/OSHA specification. The CBC 1003.3.3 Stairways and Landings model code states these stairway specifications:

Private stairways shall be a minimum of thirty-six inches wide. Trim and handrails may not encroach into this minimum width by more than 3 1/2 inches.

The maximum rise of each step is eight inches;

the minimum rise is four inches.

The minimum run is nine inches.

The largest tread width or riser height in any flight of stairs shall not exceed the smallest by more than 3/8 inch.

(2) Railings and toeboards meeting the requirements of Article 16 of these safety orders shall be installed around stairwells.

(b) The following requirements apply to all stairways as indicated:

(1) Temporary stairways that will not be a permanent part of the structure on which construction work is being performed shall be at least 24 inches in width. The stairway shall have landings at each floor, or level, of not less than 30 inches in the direction of travel and extend at least 24 inches in width at every 12 feet or less of vertical rise.

(2) Stairs shall be installed between 30° and 50° from horizontal.

(3) Riser height and tread depth shall be uniform within each flight of stairs, including any foundation structure used as one or more treads of the stairs. Variations in riser height or tread depth shall not be over 1/4-inch (0.6 cm) on any stairway.

(4) Where doors or gates open directly on a stairway, a platform shall be provided, and the swing of the door shall not reduce the effective width of the platform to less than 20 inches (51 cm).

(5) Unprotected sides and edges of stairway landings shall be provided with railings. Design criteria for railings are prescribed in Section 1620 of these safety orders.

(6) Metal pan landings and metal pan treads, when used, shall be secured in place before filling with concrete or other material.

(7) All parts of stairways shall be free of hazardous projections, such as protruding nails.

(8) Slippery conditions on a stairway shall be eliminated before the stairway is used to reach another level.

(c) Stair rails and handrails. The following requirements apply to all stairways as indicated:

Some codes (CA/OSHA Title 8 Section 1626) may cause a little confusion between the definition of handrail and guardrail, by adding a third term, "stair rail":

(1) Stairways having four or more risers or rising more than 30 inches (76 cm), whichever is less, shall be equipped with:

(A) At least one handrail and

(B) A stair rail consisting of a top rail and mid-rail along each unprotected side or edge.

See RAILING CODES & SPECIFICATIONS for model building code specifications of when a handrailing is required, heights, stairway widths, graspability, etc.

See HANDRAILS & HANDRAILINGS for more handrail and stair rail code & construction details

At least in the 2006 IRC Section R202 these terms are defined clearly:

Definition of guardrail or guard: Guard [or guardrail or guard railing]: A building component or a system of building components located near the open sides of elevated walking surfaces that minimizes the possibility of a fall from the walking surface to a lower level.


Definition of "stair rail" as guardrail: In general people speak of guardrails or guards as installed along balconies or elevated walkways and decks. When we enclose open side(s) of a stairway with a "guardrail" some codes such as the 2006 IRC Section R202 use the unfortunate term "stair rail".

More unfortunate if readers don't continue along to discover that the horizontal members described in ((B) above must be further enclosed with balusters.

Definition of handrail or hand railing: Handrail [or hand railing] . A horizontal or sloping rail intended for grasping by the hand for guidance or support.

See HANDRAILS & HANDRAILINGS for details about stairway handrailing dimensions, graspability, railing heights, railing continuity, termination, projection distances and all other parameters.

(d) Temporary Service [stairs] - Temporary service stairs, treads, landings:

The following requirements apply to all stairways as indicated:

(1) Except during stairway construction, foot traffic is prohibited on stairways with pan stairs where the treads and/or landings are to be filled in with concrete or other material at a later date, unless the stairs are temporarily fitted with wood or other solid material at least to the top edge of each pan.

(2) Except during stairway construction, foot traffic is prohibited on skeleton metal stairs where permanent treads and/or landings are to be installed at a later date, unless the stairs are fitted with secured temporary treads and landings long enough to cover the entire tread and/or landing area.

(3) Treads for temporary service shall be made of wood or other solid material, shall cover the full width and depth of the stair and shall be supported to prevent undue deflection.

(4) Temporary treads and landings shall be replaced when worn below the level of the top edge of the pan.

Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.

Dimensions Stairway Chair Lifts

Reader Question: 10 Feb 2015 Do exterior concrete stairs leading to two terraces apartments have to be a certain width? One owner wishes to put in chairlift up side of staircase railing. Stairs are 84cm wide. said:

Do exterior contrite stairs leading to two terraces apartments have to be a certain width? One owner wishes to put in chairlift up side of staircase railing. Stairs are 84cm wide.


Stairway width (in the U.S. - you don't say where you are located) should be equal to or greater than 36" of clear unobstructed distance measured at all points above the [permitted] hand-railing height.

Please see details about stairway lifts now found at STAIRWAY CHAIR LIFTS


Continue reading at STAIR HEADROOM or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see STAIR DIMENSIONS & SPECIFICATIONS FAQs questions & answers posted originally at this article

Or see these articles on stair construction

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STAIR DIMENSIONS, WIDTH, HEIGHT at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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