Mezzanine Floor Staircases

Staircase design is covered by (amongst others) BS5395: Part 1, BS5395: Part 3 and BS5950: Part 5. General guidance on staircase design is contained within the new Approved Document Part K – 2013 (Section K1 – Stairs, Ladders and Ramps) and Approved Document Part B (Section B1 – Means of Warning & Escape) of Building Regulations. This approved document supersedes previous guidance in Approved Documents Part M and Part K relating to staircases and guard railing.

Different configurations of stair landings may be required for different situations. Typical scenarios where they are required are as follows;

• If stairs run parallel with the mezzanine edge, then a top landing will be required.
• If stairs turn 90 degrees, then a mid-landing is required.
• If stairs turn 180 degrees, then a double mid landing is required.

There are a few options for staircases within Part K1 of the Building Regulations

• Private stair (only for domestic dwelling projects)
• General Access Stair
• Utility Stair

General guidance on the requirement and characteristics are shown below:

Most new mezzanine floors are required to have a minimum of one General Access Stair. Where a floor has only one access stair, it must almost always be of the General Access stair type, though a lower standard may apply where the access is used only for maintenance.

Other stairs can be usually be deemed to be for escape purposes only and be of the Utility Stair type. The width and number of stairs required is dependent on the number of persons using the floor area and travel distances to a place of safety.

General Access Stair (Industrial):

The General Access Stair requires a clear width between enclosing walls strings or upstands of 1200mm, and a minimum width between handrails of 1000mm.
This stair must always have ‘CLOSED’ risers. Treads with contrasting nosing will be governed by a rise of 150mm (MIN) to 170mm (MAX) and going of 250mm (MIN) to 400mm (MAX).

The maximum number of rises allowable is 12 per flight, except in a ‘small and/or restricted’ premises, where 16 rises are allowable.

Handrail needs to be contrasting and be a minimum of 50mm diameter (50×25 RHS is acceptable), and this must protrude 300mm beyond both the top and bottom tread nosing, unless it causes an obstruction to a common access route.

The General Access Stair (Industrial) would have 1000mm between handrails, have OPEN rises – standard up stand within industrial/storage premises and CLOSED rises – within office/retail premises.

Treads with contrasting nosing will be governed by a rise of 150mm (MIN) to 170mm (MAX) and going of 250mm (MIN) to 400mm (MAX).

The maximum number of rises allowable is 12 per flight, except in a ‘small and/or restricted’ premises, where 16 rises are allowable.

Handrail needs to be contrasting and be a minimum of 50mm diameter (50×25 RHS is acceptable), and this must protrude 300mm beyond both the top and bottom tread nosing, unless it causes an obstruction to a common access route.

The General Access Stair (Public Access) would be the same as the General Access Stair (Industrial) but requires a clear width between enclosing walls strings or upstands of 1200mm, and a minimum width between handrails of 1000mm. This stair must always have ‘CLOSED’ risers.

The Utility Stair would have a minimum of 800mm between handrails and have OPEN rises. The minimum allowable may be greater than this dependent upon the number of people the stair serves and the building function.

Treads with contrasting nosing will be governed by a rise of 150mm (MIN) to 190mm (MAX) and going of 250mm (MIN) to 400mm (MAX).

The maximum number of rises allowable is 12 rises per flight, except in a ‘small and/or restricted’ premises, where 16 rises are allowable.

Handrail needs to be a minimum of 50mm diameter (50×25 RHS is acceptable).

• Materials for treads should not present a slip hazard, especially when wet.

• Tread nosings should be highlighted with a permanently contrasting material 55mm wide on both the tread and the riser.

• No doors should swing across landings.

• The overlap of treads should be no more than 25mm and avoided if possible.

• There is a continuous handrail on each side of a flight and landings.

• The vertical height to the top of the upper handrail from the pitch line of the flight of stairs is between 900mm and 1100mm, and from the surface of a landing is between 900mm and 1100mm.

• The clearance between the handrail and any adjacent wall surface is between 60 and 75 mm.

An ‘Access Strategy Statement’ may sometimes be used to overcome the requirement to provide a Disabled Persons Platform Lift by siting the provision of a General Access Stair (for Ambulant Disabled use) in lieu, and ensuring that all facilities and areas found on the mezzanine level are replicated on the accessible ground floor.