Understanding Code Requirements for Open Stairs

Open staircases are a type of staircase construction that does not have closed sides or backsplashes. They have no risers between the treads, which reduces the obstruction of the view to a greater extent, so open staircases look more airy and light. An open staircase has many aesthetic advantages, but it also requires more consideration for safety and stability. This article will provide an in-depth breakdown of open staircase code requirements.

About open staircases

The difference between an open staircase and a traditional staircase

Open staircases	Traditional staircase

appearance

• Open staircases: Typically do not have risers, allowing visibility of the space beneath the staircase. This design gives the staircase a more transparent and modern appearance.
• Traditional staircase: there are risers set and the treads are closed to each other. It makes the stairs appear more stable and safe.

structure

• Open staircases: Since open staircases do not have risers, more attention is paid to structural strength to ensure the safety of the staircase.
• Traditional staircases: Traditional staircases are simpler in construction, with risers providing additional support, making construction more common.

visual effect

• Open staircase: it can increase the sense of space and make the space look more open from the viewpoint. Suitable for modern, simple home style.
• Traditional staircase: gives a stable visual effect. Suitable for classic and traditional home styles.

safety

• Open staircases: because risers are usually not provided, for safety reasons, openings at the riser location shall not permit the passage of a 4-inch-diameter sphere.
• Traditional staircases: Due to the presence of risers, the gaps between the treads are reduced, making the staircase relatively safer and less likely to pose a falling risk.

Scenarios for the use of open staircases

residence

• In households that enjoy socializing and interaction:Facilitates communication among family members.
• In small flats, duplexes, or more compact spaces: the open-plan design allows light to flow freely and increases the comfort of the space.
• In minimalist design homes: open-plan layouts are better suited to minimalism.
• Multi-functional areas in the home: such as open-plan family office spaces, study areas, entertainment zones, etc. Combining multiple functions in a large space.

commercial building

• Retail space: Enhances the visual experience for buyers, allows easy movement between floors, and provides the ability to browse surrounding products at any time.
• Exhibition and display space: Facilitates smooth movement for visitors and provides opportunities to view exhibits from different angles. The openness of the stairs does not obstruct sightlines, thereby maximizing the space available for showcasing exhibits.
• Restaurants and hotels: Open staircases connect the lobby with the dining area, bar, or banquet hall while also serving as a design feature. They enhance the sense of luxury in the space and easily guide guests to different areas.
• Office buildings: Open staircases connect open work areas on different floors. They enhance the visual effect of the space while promoting communication and collaboration among employees.

Building Codes and Standards

Differences in Applicability Between IBC and IRC

• IRC (International Residential Code): Specifically addresses the design and construction of single-family homes, duplexes, and small residential buildings of three stories or less.
• IBC (International Building Code): Applicable to all types of buildings, including commercial buildings, industrial buildings, high-rise buildings, public buildings, and multi-family residential buildings. It covers a wide range of building types.

IRC

The following regulations are extracted from 2024 International Residential Code without Energy (IRC) R318.7, Some notes are included to aid understanding.

Width

• Stairways shall be not less than 36 inches (914mm) in clear width at all points above the permitted handrail height and below the required headroom height.

——Note: "headroom height" refers to the vertical distance between the stair tread (or landing) and any overhead structure or obstruction.

• The clear width of stairways at and below the handrail height, including treads and landings, shall be not less than 31 1/2 inches(787mm) where a handrail is installed on one side and 27 inches (698mm) where handrails are installed on both sides.

Headroom

• The headroom in stairways shall be not less than 6 feet 8 inches (2032mm) measured vertically from the sloped line adjoining the tread nosing or from the floor surface of the landing or platform on that portion of the stairway.

Vertical rise

• A flight of stairs shall not have a vertical rise greater than 12 feet 7 inches (3835mm) between floor levers or landings.

Walkline

• The walkline across winder treads and landings shall be concertric to the run and parallel to the direction of travel entering and exiting the turn.
• The walkine shall be located 12 inches (305mm) from the inside of the run.
• The 12-inch (305mm) dimendion shall be measured from the widest point of the clear stair width at the walking surface.
• Where winders are adjacent within a flight,the point of the widest clear stair width of the adjacent winders shall be used.

Risers

• The riser height shall be not more than 7 3/4 inches (196mm).The riser height shall be measured vertically between leading edges of the adjacent treads.
• The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5mm).
• Rises shall be vertical or sloped from the underside of the nosing of tread above at an angle not more than 30 degrees (0.51 rad) from the vertical.
• At open risers, openings located more than 30 inches (762mm), as measured vertically, to the floor or grade below shall not permit the passage of a 4-inch-diameter (102mm) sphere.

Treads

• The tread depth shall be not less than 10 inches (254mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge.
• The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5mm).

Winder treads

• Winder treads shall have a tread depth of not less than 10 inches (254mm) measured between the vertical planes of the foremost projection of adjacent treads at the intersections with the walkline.
• Winder treads shall have a tread depth of not less than 6 inches (152mm) at any point within the clear width of the stair.
• Within any flight of stairs, the largest winder tread depth at the walkline shall not exceed the smallest winder tread by more than 3/8 inch (9.5mm).
• Consistently shaped winders at the walkine shall be allowed within the same flight of stairs as rectangular treads and shall not be required to be within 3/8 inch (9.5mm) of the rectangular tread depth.

Nosings

• Treads, landings and floors of stairways shall have a radius of curvature at the nosing not greater than 9/16 inch (14mm) or a bevel not greater than 1/2 inch (12.7mm).
• A nosing projection not less than 3/4 inch (19mm) and not more than 1 1/4 inches (32mm) shall be provided on stairways.
• The greatest nosing projection shall not exceed the smallest nosing projection by more than 3/8 inch (9.5mm) within a flight of stairs and the landings at the top of flight.

Landings for stairways

• There shall be a floor or landing at the top and bottom of each flight of stairs. The width perpendicular to the direction of travel shall be not less than the width of the flight served.
• For landings of shapes other than square or rectangular, the depth at the walk line and the total area shall be not less than that of a quarter circle with a radius equal to the required landing width.
• Where the stairway has a straight run, the depth in the direction of travel shall not be less than 36 inches (914mm).

Stairway walking surface

• The walking surface of treads and landings of stairways shall be sloped not steeper than 1 unit vertical in 48 units horizontal (2-percent slope).

Handrails

• Handrails shall be provided on not less than one side of each flight of stairs with four or more risers.

Spiral stairways

• The clear width at and below the handrails at spiral stairways shall be not less than 26 inches (660mm) and the walkline radius shall be not greater than 24 1/2 inches (622mm).
• Each tread shall have a depth of not less than 6 3/4 inches (171mm) at the walkline.
• Treads shall be identical, and the rise shall be not more than 9 1/2 inches (241mm).
• Headroom shall be not less than 6 feet 6 inches (1982mm).

IBC

The following regulations are extracted from 2024 International Building Code (IBC),Some notes are included to aid understanding.

Headroom

• Stairways shall have a headroom clearance of not less than 80 inches (2032mm) measured vertically from a line connecting the nosing.
• Such headroom shall be continuous above the stairway to the point where the line intersects the landing below, one tread depth beyond the bottom riser.
• The minimum clearance shall be maintained the full width of the stairway the landing.

Walkline

• The walkline across winder treads shall be concentric to the direction of travel through the turn and located 12 inches (305mm) from the side where the winders are narrower.
• The 12-inch (305mm) dimension shall be measured from the widest point of the clear stair width at the walking surface of the winder.
• Where winders are adjacent within the flight, the point of widest clear stair width of the adjacent winders shall be used.

• stair riser heights shall be 7 inches (178mm ) maximum and 4 inches (102mm) minimum.
• The riser height shall be measured vertically between the nosings of adjacent treads or between the stairway landing and the adjacent tread.
• Rectangular tread depths shall be 11 inches (279mm) minimum measured horitontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's nosing.
• Winder treads shall have a minimum tread depth of 11 inches (279mm) between the vertical planes of the foremost projection oo adjacent treads at the intersections with the walkline and a minimum tread depth of 10 inches (254mm) within the clear width of the stair.

Dimensional uniformity

• Stair treads and rises shall be of uniform size and shape. The tolerance between the largest and smallset riser height or between the largest and smallest tread depth shall not exceed 3/8 inch (9.5mm) in any flight of stairs.
• The greatest winder tread depth at the walkline within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5mm).

Nosing and riser profile

• Nosings shall have a curvature or bevel of not less than 1/16 inch（1.6mm）but not more than 9/16 inch (14.3mm) from the foremost projectiom of the tread.
• Risers shall be solid and vertical or sloped under the tread above from the underside of the nosing above at an angle not more than 30 degrees (0.52 rad) from the vertical.

Nosing projection size

• The nosings shall project not more than 1 1/4 inches (32mm) beyond the tread below。

Nosing projection uniformity

• Nosing projections shall be of uniform size, including the projections of the nosings of the floor or landing at the top of a flight.

Vertical rise

• A flight of stairs shall not have a vertical rise greater than 12 feet (3658mm) between floor levels or landings.

Spiral stairways

• Spiral stairways are permitted to be used as a component in the means of egress only within dwelling units or from a space not more than 250 square feet (23㎡) in area and serving not more than five occupants, or from technical production areas in accordance with section 410.5.
• A spiral stairway shall have a 6 3/4-inch (171mm) minimum clear tread depth at a point 12 inches (305mm) from the narrow edge.
• The risers shall be sufficient to provide a headroom of 78 inches (1987mm) minimum,but riser height shall not be more than 9 1/2 inches (241mm).
• The minimum stairway clear width at the below the handrails shall be 26 inches (660mm).

Conclusion

Based on the above reading, you should now have a good understanding of open staircase code requirements. If you want to learn more about the regulations, you can consult the relevant codes. If you're interested in this type of staircase, let's work together to create your ideal open staircase! Our designers are always ready to assist you.

FAQ

What is an open plan staircase?

An open staircase is a modern design type of staircase. It is characterised by the absence of risers and a gap between the treads. Open staircases are therefore visually lighter and more airy. However, because of the structure, it also requires more consideration for safety.

How many steps can i have without a railing?

According to the 2024 International Residentical Code without Energy (IRC), handrails shall be provided on not less than one side of each flight of stairs with four or more risers.Therefore, handrails can be dispensed with when there are 3 steps or less. However, the specific requirements need to be referred to the local regulations.