When Metal Makes Sense
Metal roofing is rarely the right answer for a traditional Victorian or Edwardian terrace — the aesthetics just don't work on an older house. Where metal really shines is:
- Modern architect-designed houses where the roof is a design feature
- Extensions and garden rooms where a low-pitch clean-lined roof is wanted
- Barn conversions and rural self-builds (especially in agricultural vernacular)
- Commercial units, workshops, and industrial properties
- Listed buildings where traditional lead would work but has been the target of theft
Modern metal roofs can be specified at very low pitches (down to 3° for standing seam, lower for mechanically-fixed profiled sheet), which makes them a good choice for extensions where a traditional tiled pitch would look too steep or too dominant.
Standing Seam Zinc and Aluminium
Standing seam is the premium metal roofing system — long sheets with upstanding seams running down the slope, locked together by folding the edges over each other. The result is a completely watertight roof with no exposed fixings, no sealants, and a cleanly modern appearance. VMZINC, Rheinzink and Kalzip are the big names. Lifespan is 60 to 100+ years depending on the metal.
Natural zinc develops a protective patina within a few years and then stays looking the same for the rest of its life. Aluminium is lighter and can be factory-coated to any colour. Both need specialist installation — the seam-folding tool (either hand-operated or motorised) and the setting-out of the roof are very different from a tile or slate job.
Profiled Steel Sheet
For commercial, agricultural and some domestic applications, coated profiled steel sheet is the cost-effective metal roofing option. Big sheets, fast to fit, reliable. Tata Steel Colorcoat HPS200 is the spec most agricultural buildings now use, with a 40-year warranty. The modern polyester and PVDF coatings don't fade or chalk the way old corrugated iron did.
For domestic work, profiled steel in a tile-effect profile (Tata Steel Britmet, for example) gives you something that looks like tiles from street level but installs on much lower pitches (down to 10°) and weighs a fraction of clay or concrete. It's a valid option for extensions and outbuildings.
Metal Over Existing Roofs
In some circumstances — barn conversions, agricultural buildings, commercial properties with failing asbestos cement roofs — it's possible to fit metal over the existing roof rather than stripping first. This is only appropriate where the existing structure will take the load, the existing covering is weatherproof (or close to it), and the details can be properly worked out. We'd inspect and specify before recommending this approach. In most cases, stripping first and starting clean is the better engineering answer.
What It Costs
Standing seam zinc on a domestic extension runs about £180 to £250 per square metre fitted, which is roughly 2.5x the cost of slate. Aluminium standing seam is similar. Profiled steel on an agricultural or commercial job is much cheaper per square metre — £35 to £70 fitted depending on insulation build-up and access. Tile-effect steel for domestic sits between the two at roughly £90 to £130/m².
Every project gets a detailed takeoff and fixed quotation. The design implications of metal (flashing details, eaves, ridges, valleys) are more complex than conventional roofing, so we always want to see drawings before quoting.
