What is mezzanine floor fire protection and why is it necessary?
So called ‘fire protection’ is effectively insulation of the mezzanine floor steelwork to prevent it from heating up quickly in a fire. Unprotected steelwork heats up quickly and can suddenly collapse. Fire protection is specified for a certain period of time such as ‘half hour’, ‘1 hour’, ‘2 hour’ or ‘4 hour’. The time period refers to the time that the protected elements remain structurally sound in the event of a fire. The fire protection required for different parts of buildings is specified within the Building Regulations part B.
Fire protecting building elements in accordance with the regulations is a statutory requirement, protecting lives and property and enabling the fire brigade to assess how long they can safely fight a fire before a risk of collapse.
Providing fire protection to mezzanine floors is also referred to as ‘fire rating’ them, and a mezzanine floor fitted with fire protection may be referred to as ‘fire rated’.
Do mezzanine floors always need to be fire protected?
The requirement for fire protection depends upon the use, size and extent of the mezzanine floor. Mezzanine flooring that is less than 10m x 10m in size, and occupying less than 50% of the area of the building in which it is located and which is not permanently occupied and infrequently accessed (used for storage) does not need to be fire rated.
Mezzanine flooring that is less than 20m x 20m in size, and occupying less than 50% of the area of the building in which it is located and which is not permanently occupied and infrequently accessed (used for storage) does not need to be fire rated as long as it is fitted with an appropriate fire detection and alarm system.
Any mezzanine floors that are permanently occupied regardless of size will need to be fire protected such as office areas, assembly and manufacturing, packing, canteen space or areas such as retail space with public access. Also mezzanines larger than 10m x 10m without an appropriate fire detection and alarm system, all mezzanines larger than 20m x 20m and all mezzanines whose size exceeds 50% of the area within which they are located. It can be seen that only in the smallest storage applications can fire protection be omitted.
How is most mezzanine flooring fire protected?
The most common means of fire protecting mezzanine floors is through the use of four key elements of insulation, column casings, a suspended ceiling, bulkheads/fascias and cavity barriers. This means of fire protecting mezzanine floors is used because of its speed of installation and low cost.
Column casings comprise a two part sheet metal case lined with ‘Promalit’ or similar board bonded to the inside of the casing. The sheet metal case usually has a galvanized or white ‘plastisol’ finish to suit the application, but can be stainless steel or coloured ‘plastisol’, and the two parts have an unobtrusive locking seam enabling them to be quickly and neatly fitted with a few taps from a rubber mallet.
Suspended ceilings comprise wires hung vertically on clips from the secondary beams of the mezzanine supporting length of ceiling runner. The runners clip together and are joined in turn by intermediate lengths of ceiling runner to create a ceiling grid. Minaboard tiles are then inserted to fill the grid. The grid is commonly and most economically based around 1200mm x 600mm ceiling tiles, however by adding further intermediate 600mm ceiling runners, 600mm x 600mm tiles can be used. The tiles fitted must be certificated to provide the necessary level of fire protection when used in the grid under a mezzanine floor. This restricts the available choice of tiles and finishes.
Bulkheads or fascias (vertical barriers to close off ceiling cavities to exposed perimeters at mezzanine floor edges or voids) are achieved by creating a framework from galvanized section and cladding the framework with plasterboard to obtain the required level of fire protection in accordance with the manufacturers specifications. Our bulkheads/fascias are then decorated.
Cavity barriers are vertical barriers within the ceiling void created with mineral wool insulation to subdivide the void into compartments in accordance with the Building Regulations in order to prevent smoke or flame traveling through the ceiling void.
Alternative means of fire protecting mezzanine floors
Sometimes aesthetic or other considerations such as positive pressure fire extinguishing systems preclude the use of suspended ceilings. Alternatives include taped, jointed and decorated plasterboard ceilings on a metal furring (MF) ceiling framework and similarly boxed in columns providing flush finishes or intumescent painting of hot rolled columns and beams.
All the components of fire protection should be certified to provide the desired degree of protection in the application in which they are being used. For example it is not acceptable to use any old suspended ceiling below a mezzanine floor; the ceiling tile and grid system must have certification specifically providing the required level of protection under a steel joist type mezzanine construction, which significantly restricts the range of manufacturers able to offer a suitable product.
This general information relates to mezzanine flooring fire protection in England and is intended for guidance only. Each application needs to be assessed on its own merits.
It is always prudent to discuss your specific project with an approved inspector or building control officer prior to commencing work, a task with which your mezzanine floor contractor will be prepared to assist.