The Building Regulations 2010: Fire Safety, Approved Document B
(2006 edition incorporating 2007, 2010 & 2013 amendments)
The UK Regulations for fire safety in buildings are detailed in Document B. There are two sections within the Document which relate directly to Rooflights, and have the following aims:
Section B2 – Internal Fire Spread –
‘to ensure fire spread over the internal linings of buildings is inhibited.
In order to inhibit spread of fire the internal linings shall-
I. adequately resist the spread of flame over their surfaces; and
II. have, if ignited, a rate of heat release or a rate of fire growth, which is reasonable in the circumstances’
In general, the standards for internal fire spread can be achieved by meeting the requirements of either (British) BS 476
Part 7: Method of test to determine the classification of the surface spread of flame of products or (European) BS EN 13501-1: 2007 Fire classification of construction products and building elements, Part 1- Classification using data from reaction to fire tests. Where there is no classification for thermoplastic materials under BS 476 Part 7, three other ratings are used; TP(a) Rigid, TP(a) Flexible and TP(b).
Section B4 – External Fire Spread
– ‘to ensure external walls and roofs have adequate resistance to the spread of fire over the external envelope and that spread of fire from one building to another is restricted.
I. The roof of the building shall adequately resist the spread of fire over the roof and from one building to another, having regard to the use and position of the building.’
In general, the standards for external fire spread can be achieved by meeting the requirements of either BS 476 Part 3 or BS EN 13501 Part 5.
- The surface linings of walls and ceiling should normally be rated Class 1 according to BS 476 Part 7
or Class C-s3,d2 according to BS EN 15301:1
- The inner layer of a rooflight should either meet that same classification, or achieve TP(a)
- however, plastic rooflights with at least a Class 3 (BS 467 Part 7), Class D-s3,d2 (BS EN 15301:1) or TP(b) rating may be used in circumstances where the maximum area of each rooflight is less than 5m², with a minimum separation distance between each rooflight of 3m
- When used in rooflights, a rigid thermoplastic sheet product made from polycarbonate or from un-plasticised PVC which achieves a Class 1 according to BS 476 Part 7 or Class C-s3,d2 according to BS EN 15301:1 for surface spread of flame can be regarded as having a British AA designation or BROOF (t4) European classification and is therefore acceptable
- Lower classifications for the outer skin may be acceptable, but only in areas out with 6m from a boundary
Please note that single skin sheet applications must meet the requirements for both the inner lining and outer roof surfaces.
Thermoplastics- Polycarbonate and un-plasticised PVC
Thermoplastic materials; PVC, solid polycarbonate and multiwall polycarbonate, are suitable materials for a wide range of building applications. However, as the material would melt during the testing procedure, they cannot be tested under BS 476 Part 3 or BS EN 15301 Part 5.
UK Building Regulations therefore define an alternative classification for these materials;
- Polycarbonate or un-plasticised PVC which achieves Class 1, BS 476 Part 7 or Class C-s3,d2, BS EN 15301
Part 1, can also be classified AA designation or BROOF (t4) classification
- Multiwall polycarbonate which is rated Class 1, BS 476 Part 7; Polycarbonate ≥3mm thick; and solid PVC (any thickness) are rated TP(a) Rigid
- Other thermoplastics, not categorised above, can be tested according to BS 2782 and are rated TP(a) Flexible or TP(b)
GRP (Glass Reinforced Polyester)
GRP can be classified to BS 476 Part 3 & Part 7, and to BS EN 15301 Part 1 & Part 5. A variety of grades are available offering alternative fire ratings dependant on application.
I. Rigid solid pvc sheet
II. Solid (as distinct from double or multi-skin) polycarbonate sheet at least 3mm thick
III. Multi-skinned rigid sheet made from unplasticised pvc or polycarbonate which has a Class 1 rating when tested to BS 476-7:1997 or 1971 or 1987; and
IV. Any other rigid thermoplastic product, a specimen of which (at the thickness of the product as put on the market), when tested to BS 2782:1970 as amended in 1974: Method 508A Rate of burning (Labratory method), performs so that the test flame extinguishes before the first mark and the duration of flaming or afterglow does not exceed five seconds following removal of the burner
Flexible products not more than 1mm thick which comply with the Type C requirements of BS 5867-2:1980 Specification for fabrics for curtains and drapes – Flammability requirements when tested to BS 5438:1989 Methods of test for flammability of textile fabrics when subjected to a small igniting flame applied to the face or bottom edge of vertically oriented specimens, Test 2, with the flame applied to the surface of the specimens for 5, 15, 20 and 30 seconds respectively, but excluding the cleansing procedure; and
I. Rigid solid polycarbonate sheet products less than 3mm thick, or multiple-skin polycarbonate sheet products which do not qualify as TP(a) by test; or
II. Other products which, when a specimen of the material between 1.5 and 3mm thick is tested in accordance with BS 2782:1970, as amended in 1974: Method 508A, has a rate of burning which does not exceed 50mm/minute.