Case study

Mezzanine Staircases and Meeting UK Standards

Jun 15, 2023 | Mezzanine Floors

However you use your mezzanine floor, whether for office space, additional storage or retail product display, the staircase is an integral part of the solution.

A staircase is seemingly a straightforward structure until you find yourself trying to navigate the complicated set of required regulations associated with them. Whilst UK Building Regulations are purposed to ensure safety and sustainability when is comes to structural developments, they can seem complex particularly to anyone who is unfamiliar with them.

The aim of this article is to assist your understanding of regulations in relation to mezzanine floor staircases by highlighting common areas of misunderstanding and offering information with direction to official guidelines.

(Please note this article refers to current regulated guidelines and provisions only, and that these may be subject to future amendments)

The vertical connection

A mezzanine floor is an upper level platform with stairs being an essential component to the overall structure.The staircase is the vertical connection between the varied floor elevations designed to enable the independent movement of people as they ascend or descend from level to level. The structure must be functional and safe as the following components are brought together to form the inclined passageway:

  • Treads – These are a series of flat horizontal surfaces on which a person is able to step on as they journey to a different level.
  • Risers – These stand vertically to support and separate the individual steps, aiding the integrity of the structure whilst composing a steepness that is safe and comfortable.
  • Stringers – As a solid panel fitted to both sides of the flight, the stringers act to stabilise the steps whilst promoting an even weight transfer across the main supporting structural components.
  • Handrail – Purposefully placed to provide stability whilst using the steps, handrails are an important safety feature. At any point during access, users can reach for the handrail which runs the entire length of the flight, to steady them selves should they need too.
  • Balustrade – In the form of spindles or panels, the balustrade fills the vertical gap between the stringer and handrail to prevent accidental falls through the gap.

Mezzanine floor staircase

What are UK Building Regulations?

As a structural platform the mezzanine floor must be designed and installed in compliance with UK Building Regulations for which essential guidance on fire safety and fall prevention is provided by the following  documents:

  • Approved Document B, Volume 2 (for buildings other than dwellings) – Fire safety
  • Approved Document K – Fall prevention

Whilst these very detailed official documents have been approved by the Secretary of State, they should be seen as practical guidance which if followed, compliance is likely providing the installation is within the regular scope of works and you have a clear understanding of the document’s technical information. It’s also important to be aware that there are certain provisions within the documents that are require precise conformity.

How UK Building Regulations influence staircase components

Included in the approved documents is guidance and provisions related specifically to staircases being structured in buildings including those other than dwellings; however the guidance will vary in accordance to the environment in which the staircase is being constructed, and this is where the technical details can become somewhat confusing.

In order to meet mezzanine floor regulations to a passable level, you should follow the guidance that matches the circumstances of the platform use, the surrounding space and expected level of occupancy. Amongst other aspects of the build, this will influence the main staircase components in the following ways:

Treads and Risers

Current regulations state for industrial or commercial floors (i.e. not domestic) that risers must be closed in all circumstances when installing a new staircase because when open, there is an increased risk of a person catching their foot in the gap which can cause them to trip. What’s more the ability to see through the gaps beneath the steps can cause a person to feel unsteady.

The term used for the depth of the tread from front to back is “going” and there are specific provisions required for both risers and goings in terms of dimensions to manage stairway steepness and usability.

01 Measuring Rise and Going diagram

All None-Dwelling Staircases – The rise and going throughout the full length of the stairway must be invariable therefore level treads on each step is essential and any tread overlapping should be no more than 25mm. On both tread and riser, nosing of no less than 55mm wide must be applied with adequate contrasting to increase the visibility of each step edge during use and from both directions.

Utility Staircase – Rather than being used for general access day-to-day, the utility staircase is used less often with the purpose of providing the occasional maintenance access or an emergency route. These staircases must have a minimum rise of 150mm and maximum of 190mm with the going measuring a minimum of 250mm and a maximum of 400mm.

General Access Staircase – Providing comprehensive access, the risers of this staircase type should be a minimum of 150mm and a maximum of 170mm with the goings a minimum of 250mm and a maximum of 400mm.

(See pages 4 and 5 of Approved Document K for information inclusive of diagrams and tables.)

Handrails

The distance between the top of the handrail to the pitch line should be between 900mm and 1000mm and if the staircase width is wider than 1000mm, a handrail is required on both sides. Where the staircase is more than 2 metres wide, an additional handrail is required to divide the width to create sections no wider than 1000mm. The maximum handrail height after meeting the mezzanine floor edge is between 900mm and 1100mm and must incorporate a smooth finish to prevent catching.

02 handrail details diagram

See pages 14, 15 and 16 of Approved Document K for more on handrails

Balustrade

Balustrade is placed to prevent falls from beneath the handrail and must follow specific provisions and guidelines to ensure effectiveness with the environment

Public environment – In any environment where children may access the staircase, balustrades must be difficult for a child to climb making horizontal bars which are easy to clamber, an unsafe option. Any gap within the guarding must not be wide enough to allow a 100mm sphere to fit through it, as a gap this size could enable a child to slip though.

Glass panes – These can be used as guarding in light use environments such as offices or retail outlets as the risk of collisions that can result in breakage is low, although the glass must meet Legal British Standards. Look out for the EN12150 kite mark embedded into the corner of each pane. This magic code confirms that the glass has been manufactured to meet Legal British Standards where the robustness prevents the danger of large sharp pieces coming away in the event of an accidental collision. Instead much smaller and less dangerous pieces are produced in the form of a shatter.

Warehouse and factories – Glass would pose a risk due to the movement of heavy handling equipment, however robust solutions such as steel knee bars, kick plates or wired mesh would be suitable.

See page 16 & 17 of Approved Document K for more details on guarding

Headroom

In all settings, there must be at minimum of 2 metres between landing floor and ceiling and stairs and ceiling to allow adequate headroom during use.

03 Minimum Headroom Diagram

See page 7, paragraph 1.11 of Approved Document K for the official guidelines and information on staircase headroom

How many staircases do I need?

The number of staircases required for your mezzanine floor will depend on two factors:

  • The upper level occupancy volume
  • The furthest a person would need to travel from the farthest point on the upper level to the nearest exit.

In small premises, for a single staircase to be acceptable,18 metres would need to be the maximum distance from the farthest point of the mezzanine level to the building exit point. Two or more staircases/exits are required with an exit travel distance beyond 18 metres and up to 45 metres.

04 distance table for staircase quantity diagram

You will find details on maximum distances in varying premises sizes and types, including diagrams and tables in section 2: design for horizontal escape of Approved Document B, volume 2

How wide should my staircase be?

The minimum width of a staircase is normally 1200mm if enclosed by walls or 1000mm if enclosed by handrails. If the staircase exceeds 2m wide, a central handrail is required to divide the width into 1000mm wide sections.

05 Width and dividing flights diagram

Evacuation staircases

For fire escape staircases, the width should meet the width of access exits and shouldn’t narrow down at any point along the escape route. Staircases taller than 30m which exceeds 1400mm in width should be divided with a central handrail with capacity dedicated to each section. (See Approved Document B, Volume 2 Pages 30 & 31)

Should my staircase incorporate a landing?

Between each landing of a general access staircase, 12 should be the maximum number of risers unless exceptional circumstances mean that space is restricted in which case 16 would be the maximum.  For a utility staircase the maximum number of risers should be 16. Landing width and length should be no smaller than the flight width and should be without any fixed obstructions. At least one directional change is required once the risers reach a total of 36.

06 Landing details diagram.

Landings can be formed using part of a floor in the building. They should be clear of fixed obstructions with any duct or cupboard doors closed or locked.

For full details on landings for stairs see Approved Document K page 10

Can I lean on WSL?

You certainly can!! Our design team encounter UK Building Regulations on a daily basis. Their familiarity of the guidance and provisions as well as their relationships with Regulating Officers means you can turn your attention to other important matters.The initial design is created by a member of our technical team and then passed to a Regulating Officer for assessment. The officer will later visit site to asses the actual build and staircase/s to confirm the build meets the regulations before being signed off. Related documentation is then passed to you for safe keeping. WSL will arrange all of this on your behalf.

Want to know more? Contact WSL today on 0113 2045350 or email sales@wslmail.co.uk

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