Author: Steven Henshaw, Technical Director at Polyroof
Date: 20th July 2017

External Fire Spread

As the waterproofing system encapsulates the roof it effectively forms the external envelope of the building. Fire spread has always been an extremely important factor in roof design. Detailed guidance on external fire spread is contained within the building regulations and roof coverings must provide adequate resistance in respect of fire.

Please be assured that all our BBA approved Polyroof systems have been tested in terms of fire and spread of flame to DD CEN/TS 1187 : 2012, Test 4 and classified to BS EN 13501-5 : 2005 (Fire classification of construction products and building elements).

All these systems are classified as BROOF(t4) which is the highest possible European fire rating for roofs. This means that the system will enable a roof to be unrestricted under the Building Regulations.

See below for links to BBA certificates:

Internal Fire Spread

All UK building regulations (such as part B in England and Wales) give detailed guidance on internal fire spread. Internal linings such as ceilings below roofs have their own specific requirements regarding fire spread. The fire resistance requirements of the materials vary between class 3 and class 0 and are detailed within the regulations.

The fire resistance must be higher for critical areas and as such class 0 linings are required for critical areas such as circulation spaces in blocks of flats. The building designer has a responsibility to comply with the requirements with respect the correct internal linings to provide the adequate protection.

Warm Roof Insulation

Rigid PIR insulation is the most commonly used material for insulating flat roofs and for good reason as it provides excellent all round performance. It is however critical that these components are used correctly and used within a correctly designed roof. PIR insulation is designed to be contained within the roof construction between fire resistant layers which are above and below and are not designed to be exposed externally. In a correctly designed roof there will be no direct exposure to internal or external fire.

For reassurance, we have attached a link from our insulation partners Recticel-Gradient regarding the fire performance of Eurothane Liquid Roofboard (known as Polyroof RES Insulation). In addition, the behaviour in relation to fire for the insulation is contained within Section 9 of the BBA certificate BBA 95/3113. This is confirmation that the overall fire rating the roof containing the insulation will depend on the type of deck and the nature of the roof waterproof covering.

The building designer can of course therefore rest assured to know that by using the range of Polyroof BBA approved roof waterproofing systems that this will provide the highest standards in terms of meeting the required regulations for fire resistance from external spread of flame.

For more information please don't hesitate to contact our Technical Team on 0800 801 890 or email