Industrial roofing and reaction to fire. What does the sheet classification cover?

Do not assign the most favourable class on a general product page to every version in the range. Match the declaration to the quotation and to the product delivered. If a specific class is required, write its full designation in the specification. A description such as “non-combustible” alone makes it harder to establish which performance was ordered and what was installed.

A building element’s performance in a fire depends on its configuration and how that configuration was assessed. A sheet’s reaction-to-fire class cannot establish a roof’s fire resistance. Asbestos-free fibre cement may form one layer. The structure and other layers still need assessment. Nor does the sheet confer a rating established for a different assembly. Where the design specifies fire resistance, select a documented system covering the proposed build-up. Favourable descriptions of the individual materials provide no evidence of their combined performance.

Purlins, beams and other members support the roof. A mineral outer covering tells you little about how these members and their connections will perform in a fire. Check the requirements for the members, bearings and joints against the design. Fibre-cement roofing does not provide universal fire protection for the frame. A covering substitution may warrant a new assessment even where both sheets have a similar reaction-to-fire class. The load-bearing function and assembly details remain part of that assessment.

A heated building may have insulation, membranes and an internal lining beneath the covering. Each layer has its own properties and installation details. The sheets can meet their declaration while the completed assembly falls short of the design requirement. When considering a substitution, check fixings, joints and conditions of use as well as core material and thickness. Issue one agreed roof section to all contractors so they can identify any proposed combination of components from different systems and obtain confirmation before installation.

A ventilation duct, cable duct or other penetration needs a detail suitable for the full roof build-up. Keeping out rain and maintaining fire performance require distinct provisions. Cutting a hole in a sheet addresses neither on its own. Specify compatible components and the installation sequence. If the detail has a classification, check its scope and the substrates it covers. A fire-related label on a sealant cartridge does not establish suitability. Match the penetration documentation to the actual materials, opening dimensions and detail installed.

A translucent rooflight is made from a different material and needs its own reaction-to-fire declaration. Equipment and PV arrays also introduce requirements for the complete installation. Specify the exact sheet and accessory variants for the roof with its actual openings and equipment. Revisit the assessment when the roof changes. For example, a rooflight strip added after handover may fit the corrugations perfectly and still require the fire design to be reviewed.

Retain the declarations for the products installed, drawings of the assembly and photographs of significant joints. Record any assessed substitutions at handover so the sheets can still be identified years later. In the schedule, give product requirements and assembly requirements their own entries and state what each classification covers. The building manager can then plan repairs using the documented detail and check whether a replacement would change the system’s performance.

Specify product reaction to fire and whole-roof requirements separately. Check the supporting evidence against the actual layers, structure, openings and services.