The short answer
A metal roof is a good idea for some UK houses and a poor one for others. Its long life and light weight are real advantages, but rain noise, condensation if the roof is not built and ventilated correctly, higher cost than concrete tile and consent in conservation areas or on listed buildings are the usual drawbacks. The house and its setting should decide.
What metal roofing means on a UK house
Metal roofing on a house comes in two common forms. Metal tile sheets are steel or aluminium panels pressed to resemble tiles, usually finished with a stone-chip coating. Standing seam is a different system altogether: long strips with raised joints, in zinc, copper, aluminium or coated steel, often chosen for modern extensions and architectural roofs.
Both are light. A metal tile sheet weighs far less than a concrete tile roof, which suits a structure that cannot carry a heavy covering and explains its use on some extensions and outbuildings. Weight also has a regulatory side. A new covering at least 15 per cent heavier than the old needs approval and a structural check, whereas going lighter does not raise the same problem.
Published lifespans are long. MyBuilder quotes 40 to 70 years for metal roofs, while the Confederation of Roofing Contractors gives 50 years and over. A zinc manufacturer states over 100 years for zinc, and a conservation source puts well-laid copper at 80 years or more. Every figure hangs on the alloy, its coating, how exposed the site is and how well the sheets were fixed.
The drawbacks worth taking seriously
Metal is not right everywhere, and its downsides are real.
- Noise. Rain and hail on a thin sheet are louder than on tile or slate. Insulation and sound-deadening layers underneath calm it, though they cost money and need designing in from the start.
- Condensation. Metal runs cold. When moist air rising from the rooms beneath reaches the underside of the sheet, it condenses and drips. The roof needs the right underlay, a vapour control layer and ventilation, or the timbers suffer.
- Cost. Metal systems generally cost more than concrete tile, and standing seam in zinc or copper costs considerably more again because of the material and skilled fabrication.
- Appearance. A metal tile roof beside slate neighbours can look out of place, a point that matters to planners as well as to taste.
- Repair and matching. Panels are hard to match later, and a scratched or dented coating is more awkward to put right than one replaced tile.
Planning, listed buildings and conservation areas
Consent is often the deciding factor. If the house is listed, changing the roof covering normally needs listed building consent from the local council, and in Bath that council is B&NES. The council wants owners to speak to its planners first, and it classes any unauthorised alteration of a listed property as an offence.
In a conservation area, materials draw close attention. B&NES's character appraisal for the villages of Freshford and Sharpstone, for example, objects to concrete tile re-covering on the grounds that it harms the place, and an unfamiliar metal roof is likely to meet the same scrutiny. Some streets also have Article 4 directions that remove certain permitted development rights, so consult the council's policy map.
Whether a like-for-like re-cover needs permission at all is a separate question, taken up in the answer on planning rules for a re-roof. If you plan to move from slate or tile to metal, ask first and order materials afterwards.
Insurance and mortgage questions
Tell your home insurer about any change of roof material, because the policy was written on the house as it stood. Some insurers ask how a roof is built, and metal may be treated differently from tile. What insurers will and will not pay for is set out under home insurance and a new roof.
Your mortgage lender may also need to know, particularly if the change touches the structure. If you are unsure, ask your conveyancer or lender before the work begins rather than afterwards, since correcting an omission later is slower and can be more expensive than a short phone call at the start.
Questions to ask a metal roofing supplier
If you are leaning towards metal, put some specific questions to the supplier and the installer before you sign. What coating protects the sheets, and what exactly does the manufacturer's guarantee cover? Remember that a guarantee is a promise about defects and says little about service life.
Ask how condensation is dealt with in your roof build-up: which underlay is used, whether a vapour control layer is included and how the loft or rafter void will be ventilated. Ask how noise will be reduced, what the sheets are fixed with, and how flashings at chimneys, walls and valleys are formed. Lead and metal flashings both have a place, and a good installer will say which suits your junctions.
Finally, ask about repair. If a panel is dented by a fallen branch, can a matching one be obtained years from now, and who will fit it? Straight answers to these questions tell you more than a brochure does.
When metal is the right answer
Metal suits a low-pitched roof on which tiles would not work, a lightweight structure, an extension, or a modern house whose design asks for a clean line. It suits a period terrace in a street of slate much less, because matching the neighbours is both the better appearance and the safer route through consent.
On older houses we favour matching what was there: natural slate goes back as slate, and stone is matched with stone. If you are comparing metal with tile or slate, the guide to materials for a replacement roof compares the choices, and the answer on covering over an old roof explains why the existing covering comes off first. For the full service, see roof replacement in Bath.
