Bauder waterproofing systems and fire performance

Bauder waterproofing systems, with exposed membranes, achieve the highest classification for external fire penetration and surface spread of flame that denotes that they are classed as ’unrestricted’ within current Building Regulations due to the fire retardant in the cap sheets and the mineral chippings on the bitumen membrane’s surface. Building Regulations state a spread of flame allowance to the C rating as the focus is towards saving human lives with the penetration of flame rating of ‘A’, rather than protecting the building itself as a result of the fire spreading.

In roofs that incorporate non-combustible surface finishes such as stone chipping, pebbles, and paving etc. that fully cover the roof, these are deemed to fully satisfy the regulation with no testing required.

Roof insulation fire performance

Individual construction products are covered within EN 13501-1: Fire Test to Building Material for which insulation as a separate component will be encompassed and allocated a Euroclass according to their reaction to fire, again with letter classifications from A1 through to F.  On the whole, materials manufactured from plastics will achieve an E rating, which will include the insulants Expanded Polystyrene (EPS), Extruded Polystyrene (XPS) and Polyisocyanurate (PIR).

Non-combustible insulants, such as mineral wool, are clearly desirable materials to include in a flat roof specification because of fire performance, and it is important to consider and balance the factors for inclusion within a roof system.  In general, non-combustible insulants are not as thermally efficient as PIR insulation and therefore the extra thicknesses, increased weight per m3 and reduced compressive strength can be a limitation in some applications.  PIR has the advantage of being highly efficient, which reduces the height and weight of a roof covering build-up offering greater versatility on a project.

Within a Bauder warm roof waterproofing system the insulation, be it mineral wool or PIR, is not exposed and is therefore protected through the fire performance of the cap sheet and its system classification; thus both insulants conform to Building Regulations in the same way - neither one achieving a higher rating than the other.  Our BBA Certificate for BauderPIR states; ”the overall fire rating of any roof containing the products will depend on the type of deck and the nature of the roof waterproof covering.”

Bauder PIR insulation has also been tested and approved by fire experts Factory Mutual (FM), whose principle global business is the insurance of buildings and loss prevention.  FM currently offers PIR insulation within a flat roof just the same as they would mineral wool without an exclusion or premium adjustment to the building owner provided that they are installed as part of a FM Approved Assembly, i.e. a stated system configuration.  Bauder PIR, as with all other products with FM Approval, are under regular surveillance by the insurer to confirm performance on buildings.

Inverted roof constructions also generally use plastic-based insulants such as EPS and XPS, though these are only used when they are fully covered with paving slabs etc and are therefore deemed to meet Building Regulations without testing.

In summary

The Bauder waterproofing systems meet current Building Regulations for fire performance and our BBA certificates state, “the systems, when used in a suitable specification, will enable a roof to be unrestricted under the Building Regulations”, which confirms they are appropriate for use on any part of a roof.

More information about fire standards and building regulations for flat roofs ►