Two kinds of metal roof
Standing seam roofs are made from long metal trays joined by raised seams that run from ridge to eaves. They are fixed with hidden clips, so there are no screw holes through the weathering surface, and the clips let each tray expand and contract with temperature. Zinc and coated steel are the usual choices, with copper for special projects.
Profiled sheet roofs use corrugated or box-profile steel sheets screwed through to purlins. They are quick to fit and economical over large spans, which is why you see them on industrial units, barns and stores across the county.
Standing seam for homes and extensions
Standing seam suits contemporary extensions, garden rooms, dormers and low-pitched roofs where tiles won't work. One manufacturer's installation guide gives a minimum finished pitch of 3 degrees for its zinc standing seam system, far lower than any tile, although each system has its own limits and we always follow the maker's figures.
What it needs underneath
Zinc and steel need the right substrate. On a cold, ventilated roof the metal sits on boarding with a continuous ventilated air gap between the boarding and the insulation, so moisture can escape. Warm roof versions need a fully supported vapour control layer and the exact build-up the manufacturer specifies. Getting this wrong can lead to corrosion from the underside and early failure.
Pros and cons
- For: very low pitches possible, long life when detailed well, light weight, clean modern lines, and little maintenance beyond keeping gutters clear.
- Against: higher material and labour cost than most tiles, specialist installation, and a look that won't suit every street. In conservation areas, or near listed buildings, check with the council's planning team before choosing metal for a visible roof.
What fitting involves
We check the structure and falls, lay the deck and any insulation, then fit an underlay or separating layer if the system needs one. Trays are formed to length, clipped down and seamed together, and the eaves, verges, ridge and abutments are finished with folded metal details so water is shed at every edge. Gutters and outlets are sized for the roof area.
Rain noise is mostly a problem on thin, uninsulated sheets. A standing seam roof on a solid deck with insulation below is much quieter than many people expect.
Profiled sheet roofs on garages, units and farm buildings
Coatings and corrosion
Steel sheets are galvanised and then coated. Thicker plastisol coatings resist scratching and generally last longer before they need attention than thinner polyester paint finishes. Over time the cut edges, laps and fixing holes are where rust usually starts, especially near the coast at places such as Watchet, Burnham-on-Sea and Portishead, where salt air speeds up corrosion.
Condensation
Single-skin sheets with no insulation often drip with condensation on cold mornings. New sheets can be supplied with an anti-condensation fleece on the underside, which holds the droplets until they evaporate. It only works with good ventilation and a reasonable pitch; one supplier recommends 10 degrees or more. Heated or occupied buildings are better served by insulated sheets or a built-up insulated system.
Repair, over-clad or replace
- Repair: replacing damaged sheets, failed fixings and washers, rooflight panels and flashings.
- Over-clad: fixing a new sheet roof over the old one, often with insulation between, so the building stays in use.
- Replace: stripping and re-sheeting where the old sheets or fixings have failed throughout.
Older roofs may have asbestos cement sheets rather than metal. Those are fragile and need careful handling; our roofing for businesses and farms page explains how we approach them.
Metal alongside other roof work
Metal often appears in small doses on traditional houses: a zinc dormer, a canopy over a door, a bay roof. Lead remains the traditional choice for flashings and small roofs, and our traditional leadwork page covers it. For low-pitched extension roofs where you are weighing metal against membranes, compare our EPDM, GRP and felt flat roof options.
How we quote
We measure the roof, check the structure and existing build-up, ask how the space below is used, and send a written quote that names the system, the coating or finish and the insulation. Speak to us on 07933 861 087, write to hello@somersetroofing.co.uk, or ask about a metal roof through the site. There is no call-out fee.
Metal Roofs: common questions
What is the lowest pitch a metal roof can have?
It depends on the system. Standing seam zinc and steel can go much lower than tiles; one major zinc manufacturer gives a minimum of 3 degrees for its standing seam system. Profiled sheets need more, and the right figure varies with the profile, sheet length and end laps. We always follow the manufacturer's limits for the specific product rather than a rule of thumb.
Is a metal roof noisy in the rain?
Thin, uninsulated sheets on a barn or garage can be loud in heavy rain. A standing seam roof on a home is different: it sits on a solid deck with insulation below, which dampens the sound considerably. If noise is a concern for a living space, we can explain the build-up that helps reduce it before you choose.
Can you stop my garage roof dripping condensation?
Usually. On uninsulated metal sheets, condensation forms when warm, moist air meets the cold metal. Options include improving ventilation, replacing the sheets with ones that have an anti-condensation fleece on the underside, or fitting insulated sheets. The fleece works best on well-ventilated buildings with a reasonable pitch, so we'll check how your garage is used first.
Is zinc a good choice near the coast?
Zinc can be used in coastal areas, but salt air is more aggressive on all metals, and the detailing and ventilation beneath the zinc need to be right. If your home is close to the sea, we'll check the manufacturer's advice for that exposure, and the finish and fixings it calls for, before recommending zinc, coated steel or another material.
Do I need planning permission for a metal roof?
Possibly. Planning Portal guidance says roof work that doesn't materially change a house's appearance usually doesn't need permission, but switching from tiles to metal on a visible roof may well count as a material change. Conservation areas, listed buildings and Article 4 directions add further controls. Check with your council's planning team before committing to metal.
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