Stair steps in Dubai: riser height, tread depth, landings and handrails

The basic rule for a stair step

Clause B.6.4.1.4 requires stair riser height, measured as shown in its Figure B.29, to be in the range 100 mm to 180 mm. Riser heights are to be as uniform as possible throughout each flight between landings, and where they are adjusted to make the treads and flight work, the difference within a single flight must not exceed 10 mm.¹

The same clause requires treads at least 280 mm deep, a tread slope of no more than 21 mm per metre (2%), and no more than 10 mm difference in tread depth within a flight. It then points to B.6.4.1.6 for further recommendations on regular-use stairs and external steps.¹

Tread, riser, nosing and flight

The Code defines a tread as the stepping space in a flight where the foot is set, and a riser as the near-vertical element forming the space between one step and the next.⁶⁷ A nosing is the projecting front edge of a tread or landing, which may be rounded, chamfered or otherwise shaped.⁸

A flight is a continuous run of treads from one landing to another.⁹ A landing is the floor area at the top of a flight or between two flights.¹⁰ A stairway is one or more flights, interior or exterior, with the landings and platforms that make a continuous passage between levels, while the staircase is the space inside the building in which the stairs are built.⁶

Which kind of stair it is

Part A states that villas and townhouses are addressed in Part K.¹¹ Part K is a standalone part for detached villas and townhouses of not more than three storeys, and a villa or townhouse converted to retail, restaurant, clinic or other non-residential use conforms to Parts A to J instead.¹²

For other buildings, Part B’s stair section begins by sending the number of exit stairways, their width, separation, exit discharge and fire rating to Chapter 3 of the UAE Fire and Life Safety Code. It states that its own architectural stair requirements align with or exceed that code.¹³

• General stairs under Part B: risers 100 mm to 180 mm and treads at least 280 mm deep, B.6.4.1.4.¹
• Building entrance steps, landscaping steps and external circulation: required to meet Table B.6, which sets treads of at least 300 mm, risers of 150 mm to 165 mm and between 2 and 14 steps per flight, B.6.4.1.6(a).²
• Regular-use stairs inside buildings that serve as a primary means of vertical circulation: conformity to Table B.6 is recommended, B.6.4.1.6(b).²
• Villa and townhouse stairs under Part K: risers 100 mm to 180 mm and treads at least 280 mm deep, with the same 10 mm uniformity limits, K.5.5.2.3.³
• Spiral stairs under Part B: clear width at least 660 mm, headroom at least 2,030 mm, risers no more than 240 mm, treads at least 190 mm deep measured 305 mm from the narrower edge, and all treads identical, B.6.4.1.12.⁴
• Industrial equipment access under Part B: walkways, platforms, stair width, tread width and door openings at least 560 mm, tread depth at least 255 mm, risers no more than 230 mm, height between landings no more than 3,660 mm and headroom at least 2,030 mm, B.6.4.1.13.⁵

Spiral, curved and winder stairs

In Part B buildings, winders, spiral and curved stairs are not permitted in means of egress, with three exceptions: industrial occupancies where they give access to or egress from equipment areas, storage occupancies where they serve mezzanines used only for storage and not as office space, and retail areas where they serve mezzanines used for storing goods. Winders may be used in stairs that are not exit stairs, with a tread depth of at least 150 mm at the narrowest point and at least 280 mm measured 305 mm from the narrowest edge.⁴

The same clause requires handrails on spiral stairs in accordance with B.6.4.1.7 and a turn that puts the outer handrail on the right of people descending. Curved stairs need a tread depth of at least 255 mm measured 305 mm from the narrowest edge.⁴

In villas, K.5.5.2.1 permits spiral stairs, winders and open stairs for all uses other than access to and exit from basements, which need a standard enclosed exit stair of 1,000 mm clear width leading to the discharge level.¹⁴

Width, landings and headroom

Under B.6.4.1.3 all stairways have a clear width of at least 1,200 mm, measured from the wall to the clear width of the step. Handrails may project into that width by up to 100 mm on each side at a height of 865 mm to 965 mm. The width of an exit stair is set by the fire code according to the number of occupants it serves.¹³

Clause B.6.4.1.5 limits the height between landings to 3,660 mm and requires a landing at every door opening, at least as wide as the required stairway width. A door swing may not take up more than half the landing width, landings must not narrow in the direction of egress, a straight-run landing need not exceed 1,200 mm in the direction of travel, and the landing slope is limited to 2%.¹⁵

Headroom under B.6.4.1.15 is at least 2.03 m, measured vertically above a plane parallel to the most forward projection of the treads, and at least 2.3 m above landings.⁵

Part K sets villa stairways at 1,000 mm minimum clear width.¹⁴ An intermediate landing is not required in a villa whatever the floor-to-floor height, although one is recommended where that height exceeds typical practice, for example more than 4 m. Enclosed villa staircases need a landing at the door, and villa landings are at least 1,000 mm wide.¹⁶

Handrails and guardrails are different things

The Code defines a handrail as a horizontal or sloping rail for grasping by hand for guidance or support, and a guardrail as a vertical protective barrier along elevated surfaces, exposed edges of stairways, balconies and similar areas that minimises the possibility of a fall.⁹

Under B.6.4.1.7, stairs have handrails on both sides, 865 mm to 965 mm above the tread, measured vertically to the top of the rail from the leading edge of the tread. Regular-use stairs and external steps also need an additional handrail at 650 mm to 750 mm for children and people of short stature. A handrail forming part of a guardrail may be higher than 965 mm but not above 1,065 mm. Handrails stand at least 57 mm clear of the wall, are within 760 mm of every part of the required egress width, run the full length of each flight, and inside handrails continue between flights at landings. Circular handrails have an outside diameter of 32 mm to 51 mm.¹⁷

A handrail that is not circular has a perimeter of 100 mm to 160 mm, a largest cross-section dimension of no more than 57 mm and graspable edges rounded to at least 3.2 mm radius. Handrails need a reflectance contrast of at least 30 LRV points against their background, and materials exposed to the sun must not reach temperatures that can harm users.¹⁸

Clause B.6.4.1.8 requires guardrails on every stairway where the elevated surface is more than 760 mm above finished ground level, without reducing the stair’s clear width. They are at least 1,200 mm high, measured from the leading edge of the tread, or 1,065 mm where the stair handrail forms part of the guardrail. Open guardrails need intermediate rails or a pattern up to 865 mm that a 100 mm sphere cannot pass through.¹⁸ The triangle formed by the riser, tread and bottom rail at the open side of a stair must not pass a 150 mm sphere, and guardrails at landings or balconies over stairways also follow B.4.2.5.2.¹⁹

Part K is different on one point that affects many villa stairs: it requires handrails on the open side of the stair, rather than on both sides, while keeping the 865 mm to 965 mm height and the grip dimensions.²⁰ Villa guardrails are at least 1,200 mm high, or 1,065 mm where the handrail forms part of the guardrail, with the same 100 mm and 150 mm sphere rules. Part K measures guardrail height from the surface next to the guardrail, where Part B measures it from the leading edge of the tread.²¹¹⁸

External and outside stairs

Under B.6.4.1.10, an open outside exit stair is not provided in any building at more than 15 m from finished ground level. Outside stairs more than 11 m above finished ground level need an opaque visual obstruction at least 1,200 mm high, and outside stairs are separated from the interior of the building by construction with the fire-resistance rating required by Table 3.4 of the fire code.²² Part K repeats the 11 m and 1,200 mm rule for villas.²³

External steps and building entrance steps are also where Table B.6 is mandatory rather than recommended.² The additional lower handrail for children and people of short stature is required on regular-use stairs and on external steps.¹⁷

Surfaces, contrast and light

For regular-use and external stairs, B.6.4.1.6 requires a slip-resistant step edge with a reflectance contrast of at least 30 LRV points against the step surface. It recommends a warning surface at the descending edge of each flight, conforming to Part C, and says lighting along the whole flight should be at least 200 lux.²

Under B.6.4.1.14, treads and landings are free of projections or lips that could trip users and have consistent surface traction within a stairway. Where contrasting marking is used, exit stair treads carry a painted, coated or integral strip along the full width of the leading edge, 25 mm to 51 mm wide and within 13 mm of the edge. Adhesive-backed tape is not permitted.⁵ Part K repeats the trip and traction rules for villas.²⁴

Where geometry ends and structural design begins

The clauses above are architectural. The structural loads come from Part F, which takes minimum uniform live loads from Chapter 4 of ASCE/SEI 7-16 and asks for concentrated loads to be evaluated where objects create significant point loads.²⁵ Part B separately requires balcony, handrail and guardrail assemblies to withstand the loads specified in ASCE/SEI 7-16.²⁶

Scope and limits