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The Regulatory Reform (Fire Safety) Order 2005 requires building owners, including employers, to undertake comprehensive assessments to identify potential fire risks, and then take necessary measures to reduce or eliminate those risks.

Consultants and contractors therefore play a pivotal role in considering all elements of the design which may affect the fire risk assessment: including the selection of combustible materials for the construction process and, in particular, flammable insulation; or those products which are merely classified as ‘fire resistant’.

In the event of a fire event that puts people at the risk of death or serious personal injury, the RRFSO clearly states that individuals may face criminal prosecution if they have not carried out a suitable or sufficient fire assessment.

The RRFSO is applicable to buildings other than dwellings (and dwellings where a room is rented out).  It applies both during the construction phase, and in occupation.

Approved Document B

Both non-combustibility and limited combustibility are defined by, and form an important aspect of the guidance given in Approved Document B: Volume 2 - Buildings other than Dwelling Houses, April 2007 (ADB2).

ADB2 recognises that if a fire penetrates a roof near a compartment wall, there is a risk that it will spread over the roof to the adjoining space.

Specific guidance is given for ‘built-up’ flat roof constructions where the insulation and weatherproof membrane is carried over the head of a compartment wall:

Paragraphs 8.29 and 8.30 of ADB2 state that, where a compartment wall is taken up to meet the underside of this type of roof deck construction, a zone of the roof 1500mm wide on either side of the wall should have a covering of designation AA, AB or AC on a substrate or deck of material of limited combustibility.

This guidance applies to all non-domestic buildings over 15 metres high and, irrespective of height, buildings such as hospitals, schools, warehouses, factories and shopping centres.

In practical terms, this means that any insulation used in these zones must be of limited combustibility unless other measures are taken, which are proven to maintain the fire compartmentation. Such measures may include the installation of a fire-resistant ceiling to prevent fire directly attacking the underside of the roof deck or a roof system, proven by fire resistance testing not to compromise the compartment wall.

It should be noted that while rock mineral wool is frequently specified in ‘fire-stopping’ applications, plastic foam insulation products do not come within the ADB2 definitions of non-combustible or limited combustibility.


The European Reaction To Fire Classification System has been developed to compare construction products for ignitability, flame spread, heat release, smoke production and their propensity for producing flaming droplets or other potentially harmful debris. 

Prior to this legislation being implemented, EU countries had different methods for testing and classifying the Reaction to Fire performance of construction materials, thus making comparison of the resulting data extremely difficult; with manufacturers required to carry out different tests in order to sell their products into a particular country or market.

The implementation of a single classification system across the EU member states has introduced a common method for comparing the reaction to fire performance of construction products. Testing is now standardised through the use of BS EN 13501-1 ‘Fire classification of construction products and building elements’.

For insulation products intended to be used in wall and ceiling constructions, there are seven reaction to fire classification levels available - A1, A2, B, C, D, E and F.

Additional classifications provide information on a product’s tendency to produce smoke and flaming droplets or particles.

When considering combustible products, smoke release is an important consideration and is measured for reaction to fire under classes A2 to D. There are three smoke intensity levels: s1, s2 and s3, with s3 being the worst.

Burning droplets/particles can inflict skin burns and cause further spread of fire; being assessed for their reaction to fire against classes A2 to E. There are three classes of burning droplets: d0, d1 and d2, with d2 being the worst.

Although not mandatory, products achieving A1 classification are defined as non-combustible by UK Regulations, while limited combustibility products require an A2 classification or higher.

LPC Design Guide

The basic principles required to achieve adequate property and business insurance protection are defined within the Loss Prevention Council Board’s ‘Red Book’ and the LPC Design Guide for the Fire Protection of Buildings 2000, which includes the ‘Essential Principles’ document. These documents are principally concerned with reducing the risk to occupants and damage to property and business in the event of a fire, thereby minimising fire and smoke damage, and interruption to the business as a consequence.

While not mandatory, these documents encourage consultation with insurers at the earliest stage to influence insurance terms and are supplementary to the requirements of Building Regulations.

The LPC Design Guide makes specific reference to the use of non-combustible and limited combustible materials. It also introduces the concept of the ‘Protected Zone’, which includes the external roof area each side of a compartment wall. Roofs in this zone require appropriate fire resistance or alternative protection, depending on the use of the building and the associated risk.

Systems achieving LPS 1181 Ext-A meet requirements for creating a ‘protected zone’.