Can individual steel roof sheets be replaced?

One sheet is enough when the fault stays in one spot and everything around it is healthy. A forklift mast that clipped an eaves sheet, a sheet holed by a dropped tool, one panel split along a lap where a fixing has worked loose: each of these can be cured by swapping that single sheet, and nothing else needs to be touched.

The test is what surrounds the damage. We look at the sheets on either side, the laps, the fixings and the purlins, which are the horizontal rails the sheets are screwed to. If those are sound, the new sheet will sit as tightly as its neighbours and the leak stops. If the neighbours show rust, chalky paint and pitted screw heads, a new sheet in the middle only moves the leak a few metres along the slope.

Photographs of the roof come with our verdict, so you can see for yourself why we recommend one sheet, a short run of sheets or a different approach altogether. The rest of what we do on larger buildings is on our commercial roofing page.

Profiled steel comes in many shapes, and a sheet that looks close is rarely close enough. The depth of the ribs, the spacing of the crowns and the width the sheet covers all have to agree, or the laps will not seal and the new sheet will sit proud of the old. We measure the existing profile on site, keep an offcut if the shape is unusual, and order against that.

Thickness matters as well. A thinner sheet among thicker ones dents sooner and flexes underfoot. Older sheets are often factory coated, so a new sheet will look brighter than the weathered ones until it ages. If the building faces the road, tell us before we order. A coating over the whole slope can even the look out later, and our page on metal roof coating explains how that works.

Where a profile is no longer made, the choices are a close equivalent with the laps adjusted, or recovering a bigger area. You hear which before the quote arrives, never after the work has started, and the choice is explained in plain words.

Access comes first. Steel is slippery when damp, and any roof with rooflights or old sheeting can be fragile. We spread the load with crawling boards or work from a mobile platform rather than walking the sheets, and every rooflight in reach is found and covered before anyone steps near it.

The damaged sheet is released by taking out its fixings and lifting the edge of the overlapping sheet enough to slide it clear. The purlins underneath are checked for rust and movement before anything new goes down. The replacement is laid with the correct side lap and end lap, sealed with the lap sealant the system calls for, and fixed with new screws and sealing washers in the pattern the sheet was designed for. Old fixing holes are never reused, because a screw in a worn hole will not grip.

Last, we look at the laps from inside the building for daylight and, if the weather allows, test the repair with a hose working from the top down.

Corrosion rarely stops at one sheet. Steel fails first at its cut edges, at the laps and around fixings, and the trouble spreads along a slope. Our guide to cut-edge corrosion explains how it starts. If you can see orange lines along several laps, or sheets that crumble at the edge when pressed, swapping them piecemeal adds up to more money than treating the slope together.

The slope-wide job may be new sheets, a new layer over the old, or a coating system. Which one makes sense depends on the spread of the damage, the state of the purlins and how the building is used. A recovered roof also needs the structure to carry the extra layer.

You get the verdict and the reason for it, and we put forward the lesser job if it will do the work properly. Nobody gains from a replacement that a repair would have handled.

HSE says a building built or refurbished before 2000 should be treated as though it contains asbestos. Older industrial roofs were often clad in asbestos cement sheeting, and that is not a sheet you simply unscrew and bin. Our page on the asbestos cement industrial roof covers the detail.

HSE places intact asbestos cement sheets, lifted off carefully, in the non-licensed category of work. Where the sheets crack or crumble into dust, the job becomes notifiable non-licensed work, and notice is required before the work starts. The waste is wrapped twice and labelled, the sheeting goes in a locked skip, and pieces are lowered by hand, never thrown or sent down a chute.

Whatever is on your roof, we identify the material before any sheet is lifted, and a written quote naming one price comes after that check.