Metal Roofing near you

Changing to metal is a change of covering material, and that is the phrase the Building Regulations care about. The Planning Portal's re-roofing guidance states that where an existing covering is to be replaced with a different material, approval is likely to be needed to ensure the roof will be adequate for structural stability, which it says applies where the replacement will be significantly heavier or lighter than the existing, and also meets requirements for fire safety and energy efficiency. Because a roof is defined as a thermal element, it adds that the work to re-cover a roof should also include improving the thermal insulation properties of the roof.

The structural check runs through Approved Document A. Its guidance on re-covering says that where the work involves a significant change in the applied loading, the structural integrity of the roof structure and the supporting structure should be checked so that on completion the building is not less compliant with the structural requirement than the original, and it defines a significant change in roof loading as an increase of more than 15 per cent. If that check shows the construction cannot sustain the proposed increase, through overstressed members or unacceptable deflection, strengthening or replacement of roofing members is needed and the work is classified as a material alteration.

Planning is a separate question and usually a matter of appearance. The Planning Portal's position is that work to the roof of a house that does not materially affect its external appearance will usually not require planning permission, which is exactly the test a bright zinc or copper roof on a street of clay pantiles may fail. In a conservation area, or where an Article 4 direction applies, ask the local planning authority before ordering anything. On a listed building, national planning practice guidance is that works altering the building in a way that affects its character as a building of special architectural or historic interest need listed building consent, that listing normally covers the whole building inside and out, and that doing such works without consent is a criminal offence.

Metal roofing is a fabrication trade as much as a roofing one. A standing seam roof is formed from coil or sheet into panels whose upstands are folded or welted together, and the quality of the roof lives in the seams, the clips and the way the covering is allowed to move. Approved Document C recognises a roofing system in which jointless materials and sealed joints allow for structural and thermal movement, and metal moves: a slope that is pinned down so it cannot expand and contract will tear itself at the fixings or oil-can visibly across the panels.

The support beneath matters as much as the metal. Fully supported systems need a continuous deck, and Approved Document C asks that each sheet, tile and section of roof is fixed in an appropriate manner, pointing to the British Standard on workmanship for slating and tiling and, in its alternative approach, to the codes of practice for sheet roof and wall coverings in aluminium, zinc, galvanised corrugated steel and copper, and to the code of practice for fully supported lead sheet. Ask which standard the installer is working to and whether the deck under the metal is being renewed.

Then there is the interlayer detail. Metal is cold, and a cold impervious sheet over a warm, humid space is the classic recipe for condensation forming on the underside rather than rain coming through the top. Approved Document C's section on roofs covers three separate situations, including the risk of interstitial condensation within the construction and the risk of condensation or mould growth on the internal surface, and a metal roof over a habitable extension has to answer all three. The vapour control layer, the ventilation or the choice of a warm-deck build-up is the answer, and it should be on the drawing before the metal is ordered.

The weight argument usually runs in metal's favour and then has to be taken seriously in the other direction. Approved Document A's 15 per cent test is written around an increase in loading, so swapping heavy concrete tiles for a light sheet rarely overstresses anything. What it does change is how the roof resists being lifted off. The Planning Portal's loading guidance lists wind among the loads a roof carries and says the roof should be tied down to the structure to prevent lifting in strong winds, with straps of roughly 1.2 metres fixed to the wall plate and the inner skin of the wall at 2 metre centres. A lighter covering makes the fixings and the tie-down the whole of the argument.

Appearance is the constraint that actually stops most metal roofs on British houses. A standing seam roof is visually assertive, and on a street with a consistent roofscape that is precisely what the planning test about materially affecting external appearance is asking about. Rear extensions, side returns, porches, dormers and garden buildings are where metal usually goes ahead without difficulty, because the covering is barely visible from the street and the building is new work rather than an alteration to a historic elevation.

Fire performance is worth checking rather than assuming. Approved Document B sets separation distances by the type of roof covering and the size and use of the building, measured to the relevant boundary, which is the provision that matters for an outbuilding or a garage close to a neighbour. The Planning Portal separately names a new covering whose performance in a fire would be significantly different from the existing covering as a trigger for building control approval.

Ask who is notifying the work before anyone starts. GOV.UK sets out the two routes for work needing building regulations approval: apply to a building control body, either the local authority's building control department or a private registered building control approver, or use someone registered with a competent person scheme, who certifies the work themselves. GOV.UK's published list names NAPIT and CompetentRoofer, operated by the National Federation of Roofing Contractors Limited, as the authorised schemes for replacement of roof coverings on pitched and flat roofs.

Then separate the two guarantees that get confused on metal roofs. The metal itself may carry a manufacturer's warranty on the coating or the material, which is not the same thing as a workmanship guarantee from the installer who formed and fixed it, and on a hand-formed standing seam roof workmanship is where the risk lives. Get both in writing, with the exclusions, and note GOV.UK's plain warning that without approval you will not have the certificates of compliance you may need when you want to sell your home.