What is mezzanine floor fire protection and why is it necessary?

So called ‘fire protection’ is effectively insulating material of the mezzanine floor steelwork to prevent it from heating quickly in a fire. Unprotected steelwork gets hot quickly and can suddenly failure. Fire protection is specified for a certain period of time such as ‘half hour’, ‘1 hour’, ‘2 hour’ or ‘4 hour’. The period of time làm gác xép refers to the time that the protected elements remain structurally sound in the event of a fire. The fire protection required for various areas of buildings is specified within the Building Regulations part B.

Fire protecting building elements relative to 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 failure.

Providing fire protection to mezzanine floors is often known 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 utilization, 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 section of the building in which it is located and which is not permanently occupied and rarely accessed (used for storage) doesn’t have to be fire rated.

Mezzanine flooring that is less than 20m x 20m in size, and occupying less than 50% of the section of the building in which it is located and which is not permanently occupied and rarely accessed (used for storage) doesn’t have to be fire rated as long as it is fitted with an appropriate fire recognition and home security system.

Any mezzanine floors that are permanently occupied regardless of size will need to be fire protected such as office areas, assembly and manufacturing, providing, canteen space or areas such as retail space with public access. Also mezzanines larger than 10m x 10m without an appropriate fire recognition and home security system, all mezzanines larger than 20m x 20m and all mezzanines whoever size is higher than 50% of the area within that they are situated. It can be seen that only in the smallest storage applications can fire protection be disregarded.

How is most mezzanine flooring fire protected?

The most common means of fire protecting mezzanine floors is with the use of four important components of insulating material, column casings, a stopped threshold, bulkheads/fascias and tooth cavity barriers. This means of fire protecting mezzanine floors is used due to its speed of installation and low cost.

Column casings comprise a two part piece metal case layered with ‘Promalit’ or similar board bonded to the inside of the covering. The piece metal case usually has a galvanized or white ‘plastisol’ finish to suit the necessary paperwork, but can be stainless or tinted ‘plastisol’, and the two parts have an unobtrusive locking seam enabling them to be quickly and neatly fitted with a few taps from a plastic mallet.

Stopped ceilings comprise wires strung vertically on segments from the 2nd cross-bow supports of the mezzanine supporting amount of threshold jogger. The runners clip together and are joined in turn by intermediate measures of threshold jogger to make a threshold grid. Minaboard tiles are then inserted to fill the grid. The grid is usually and most cheaply based around 1200mm x 600mm threshold tiles, however by adding further intermediate 600mm threshold runners, 600mm x 600mm tiles can be used. The tiles fitted must be certificated to provide the info level of fire protection when used in the grid under a mezzanine floor. This confines the available choice of tiles and finishes.

Bulkheads or fascias (vertical barriers to shut down threshold 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 search for the required level of fire protection relative to the manufacturers specifications. Our bulkheads/fascias are then adorned.

Tooth cavity barriers are top to bottom barriers within the threshold void created with vitamin made of wool insulating material to subdivide the void into chambers relative to the Building Regulations in order to prevent smoke or flare traveling through the threshold void.

Alternative means of fire protecting mezzanine floors

Sometimes aesthetic or other considerations such as positive pressure fire extinguishing systems preclude the use of stopped ceilings. Alternatives include taped, jointed and adorned plasterboard ceilings on a metal furring (MF) threshold framework and similarly boxed in copy providing flush finishes or intumescent painting of hot thrown copy and cross-bow supports.


All the components of fire protection should be certified to provide the specified degree of protection in the application in which they are being used. For example it is not acceptable to use any old stopped threshold below a mezzanine floor; the threshold tile and grid system must have certification specifically providing the mandatory level of protection under a steel joist type mezzanine construction, which significantly confines the product range of manufacturers able to have a suitable product.

Get advice

This general information relates to mezzanine flooring fire protection in Britain and is intended for guidance only. Each application needs to be examined alone merits.

It is always prudent to discuss your unique project with an approved inspector or building control police officer prior to starting out work, a job with which your mezzanine floor contractor will anticipate to assist.

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