7.1.9 Profiled self-supporting metal roofing
Profiled self-supporting metal roofing shall be of adequate strength and durability, resist the passage of water to the inside of the building, and provide an adequate level of thermal and sound insulation.
Profiled self-supporting metal sheet roofs should be designed and constructed in accordance with:
- BS 5427 Code of practice for the use of profiled sheet for roof and wall cladding on buildings
- BS EN 14782 Self-supporting metal sheet for roofing, external cladding and internal lining. Product specification and requirements
- BS EN 14509 Self-supporting double skin metal faced insulating panels — Factory made products — Specification
- BS EN 508 — Parts 1, 2 and 3 Roof and cladding products from metal sheet. Specification for self-supporting products of steel, aluminium or stainless steel
- BS EN 506, for self-supporting copper and zinc
- BS EN 1991-1-1, 3 and 4 for structural loads and be fixed in accordance with the manufacturer’s instructions.
Profile sheet roofing can be:
- a site assembled system including self-supporting metal liner and outer metal profile. To be held apart by a site-installed structural support system, with insulation between the liner and profile layers
- factory insulated panels system ie, sandwich panels or composite panels with metal inner and outer skins factory bonded onto a thermal core insulation layer to form a composite self-supporting assembly.
An AVCL must be provided on the warm side of the insulation.
Note(s)
Subject to the profile manufacturer’s recommendations, the AVCL can be formed by sealing the side and end laps of the metal liner or by the provision of a separate AVCL membrane directly above the inner liner. The AVCL must be fully sealed around all penetrations and at the roof perimeter, and have a vapour resistance of at least 5,000MNs/g. If high-density polythene is used, it must be reinforced 1,000 gauge or more and of virgin material.
Insulation should contact both the inner and outer metal layers. Any voids formed by the profile of the outer sheet metal roof covering should be ventilated. Ventilation can be achieved by leaving open the profile at both ends of the sheeting above the insulation. If profile fillers are fitted, they should leave a free area of not less than 5% of the cross-sectional area of the void. Where the insulation is likely to be affected by local condensation, a breather membrane should be provided on top of the insulation to discharge condensate externally in accordance with the profile manufacturer’s recommendations.
The profiled panels should be fixed using suitable fixings which avoid bimetallic corrosion in accordance with the manufacturer’s recommendations.
The panel side laps and end laps should be sealed to provide an air barrier as part of the overall air leakage and vapour control requirement of the building, in accordance with the panel manufacturer’s instructions.
Last updated: 2nd January 2025