Workplace (Health Safety and Welfare) Regulations 1992 state – “Every workplace shall have suitable and sufficient lighting which shall, so far as is reasonably practicable, be by natural light”. These comments are restated in HSG38 – Lighting at Work.
The most effective method of providing even, consistent daylight, particularly in large buildings, is through rooflighting – up to three times more efficient than windows of a similar area. Diffusing materials should be used wherever possible to provide even light distribution and avoid glare. GRP is particularly effective in this respect. Wall glazing is less effective and can create internal shadows and dark corners. However it does offer good psychological benefits and must not be ignored.
In the UK, Building Regulations Approved Document B (2006 edition amended 2007) sets out the rules for fire safety of buildings. Section B2 covers internal fire spread, and applies to the linings of both the roof and walls of buildings. In general these are surface spread of flame requirements to BS476 Part 7 (typically Class 1 and Class 3) or to BS EN 13501 Part 1 (typically Class C-s3,d2 or Class D-s3,d2). Section B4 covers external fire spread and applies to external coverings or roofs and walls; in general these are fire resistance requirements to BS476 Part 3 (typically AA and AB) or to BS EN 13501 Part 5 (typically BROOF(t4)).
For the majority of industrial buildings, the requirements can be summarised as follows
- The lining of a roof or wall should normally be rated Class 1 to BS476 Part 7, Class C-s3,d2 to BS EN 13501 Part 1 or Tp(a).
- A concession allows the lining to be rated Class 3 to BS476 Part 7, Class D-s3,d2 to BS EN 13501 Part 1 or Tp(b) if the area of each rooflight is less than 5m2, and there is a clear space of 1.8 metres in all directions between each rooflight.
- There are no restrictions on use of roof outer sheets rated at least AC to BS476 Part 3 or BROOF(t4) to BS EN 13501 Part 5. Rooflights with outer skin fire ratings less than this should not be used within 6 metres of a boundary.
- A single skin sheet must meet the requirements for both the inner ceiling and outer roof surfaces.
- The only requirement for greater protection of wall outer sheets is where the building is within 1 metre of a boundary or is over 20 metres tall or is a building to which the public have access, when some areas will require sheets rated Class 0 or Class B-s3,d2 to BS EN 13501 Part 1.
For further information, consult the NARM technical committee: email@example.com
Independent research has shown that rooflights make a positive contribution to compliance with Part L of the Building Regulations. Full Guidance on use of Rooflights to help meet these requirements is given in NARM document “Designing with Rooflights: Supporting the Guidance in AD L2A & L2B (2010)”, which is a second tier document referenced from Approved Document L, and approved by the Department for Communities and Local Government.
When specifying rooflights, designers should consider carefully the potential to eliminate or reduce known or predictable hazards. The decision on how best to specify rooflights should take account of the risks associated with temporary gaps during construction, and the risks when access to the roof is needed later e.g. during maintenance or cleaning.
As in all building work good safety standards are essential to prevent accidents. In accordance with the Health and Safety at Work Act and the Construction (Design and Management) or CDM Regulations 2007 , the building should now be designed with safety in mind, not only for the construction period but throughout the normal life of the building. This must include considering the safety of people involved in maintenance and repair, and even demolition. It might mean providing permanent access to the roof, walkways and parapets, for example. The HSE document HSG 33 Safety in Roof Work refers specifically to fragile rooflights as an example of a potential hazard to be considered and to be avoided as far as possible.
Construction of the roof is one of the most hazardous operations because of the potential for falls or material dropping onto people below. The roofing contractor must plan and document a safe system of work before starting construction. This must take into account if any of the roof assembly will be fragile until fully fixed. Metal roofing systems together with appropriate rooflights, even after the first fix of lining out, can be designed to be non fragile. However until the systems are fully fixed, both metal and rooflights must be regarded as fragile.
Where specifying rooflights designers should consider the following options:
- Specifying in plane rooflights that are non-fragile.
- Fitting rooflights designed to project above the plane of the roof, and which cannot be walked on (these reduce the risk but they should still be capable of withstanding a person falling onto them).
- Protecting rooflight openings e.g. by means of mesh or grids fitted below the rooflight or between the layers of a built-up rooflight.
- Specifying rooflights with a design life which matches that of the roof, taking into account the likely deterioration due to ultraviolet exposure, environmental pollution, and the internal and external building environment.
NARM NTD03 Application of ACR[M]001 ‘Test For Non-Fragility of Large Element Roofing Assemblies’ to GRP Profiled Rooflight Sheeting can be downloaded here.