Industrial Roof Refurbishment

The five things that actually fail

An industrial roof is a large area of coated metal sheet, and the coating on the sheet is generally the most durable part of the assembly. What wears out first is everything at the edges and penetrations — which is why a roof can look serviceable from the ground and still be putting water into the building every time it rains hard.

Cut-edge corrosion is the signature industrial defect. Sheets are coated on the coil and then cut to length, which leaves the raw steel exposed at every cut edge — most importantly along the laps at the eaves. Corrosion starts at that edge, works back under the coating and lifts it, and the affected area spreads year on year. It is highly visible as a rust line along the sheet ends and it is entirely treatable while it is superficial. Left long enough it perforates the sheet.

Fasteners and washers. The sheet is fixed with thousands of screws, each with a sealing washer. Washers harden, crack and shrink under UV and thermal cycling, and the fastener itself can corrode or back out as the sheet moves. Every failed washer is a hole through the roof, positioned exactly where the water runs.

Rooflights. GRP rooflights yellow, craze and embrittle. They are the shortest-lived component on the roof by a wide margin and they are the main reason an industrial roof becomes a fragile surface. A refurbishment that renews the sheet and leaves twenty-year-old rooflights in place has replaced the durable part and kept the part that fails.

Lap seals. Side and end laps rely on sealant and on the fixing pattern holding them closed. Thermal movement over a long run works them, and once a lap opens, capillary action and wind-driven rain do the rest.

Gutters. Internal valley and perimeter gutters silt up, corrode at the joints and back up above the level of the sheet laps. This is the failure that puts water inside the building rather than down a wall, and it is the one most often missing from a quotation.

Matching the intervention to the defect

Cut-edge treatment. Where corrosion is superficial, the edge is mechanically prepared back to sound material and a purpose-made cut-edge system — a primer and a reinforced coating band — is applied along the lap. It is a targeted, relatively inexpensive operation that arrests a defect which otherwise compounds. Where the sheet has perforated, coating it achieves nothing; that area needs sheet replacement or the roof needs a different answer.

Fastener replacement. Failed fixings are replaced, generally with a larger-diameter fastener into sound material and a new sealing washer. On a roof where washer failure is widespread this becomes a systematic operation rather than a repair, and it is often the trigger for considering a full coating instead.

Rooflight replacement. Old GRP is removed and replaced with new, and this is the point to specify non-fragile rooflights so that the roof is safer to work on for the rest of its life. It is done as part of the refurbishment because the access and edge protection are already in place; doing it separately later means paying for that access twice.

Gutter lining. A cold-applied liquid lining taken through the gutter and up under the sheet ends renews the gutter without removing it, which on an internal valley gutter is a very substantial saving over replacement. It is frequently the highest-value single item in an industrial refurbishment and it is routinely omitted from quotations that price the field area and stop there.

Full roof coating. Where the defects are widespread rather than discrete, a cold-applied liquid system over the whole roof — profile, laps, fasteners and details — renews the weathering surface in one operation. It requires the sheet to be structurally sound and the preparation to be thorough, and it avoids hot works entirely, which matters where an insurer has restricted them.

When refurbishment stops being the right answer

Refurbishment treats the weathering surface. It does nothing for the structure, and the honest boundary is the condition of the liner tray and the purlins. Where those have lost section, or where the sheet has perforated across large areas, you are past refurbishment and into over-sheeting or a full strip — both covered on the industrial flat roofing page.

The other boundary is thermal. A refurbishment that renews the surface leaves the insulation exactly as it was. If the building is poorly insulated and you are spending meaningfully on the roof anyway, the question of whether to over-sheet instead — and pick up new insulation in the spacer void in the same operation — deserves a real answer rather than being defaulted past.

There is a regulatory dimension too. Renovating more than 50% of the roof surface, or more than 25% of the whole building envelope, makes the roof a controlled thermal element requiring upgrade to around 0.18 W/m²K by calculation. A coating adds no insulation, so where that trigger applies, a coating alone may not satisfy it. Establish that before pricing rather than after.

Asbestos and fragility on an older industrial roof

Industrial roofs built before 2000 may contain asbestos cement sheet or asbestos in the rooflights, and a great deal of British industrial stock sits in that window. The duty to manage means a survey and a management plan come before physical work, and the finding changes the options materially — encapsulation under a coating or a new outer skin becomes considerably more attractive than anything that disturbs the material.

Fragility governs how the work is done. Weathered profiled sheet and aged GRP rooflights will not reliably bear a person, and falls through fragile roofs and rooflights remain among the most persistent causes of serious injury in construction. The practical consequence for a building owner is that a credible quotation includes the staging, netting and edge protection to work safely across the whole roof. A price that undercuts the others substantially on a large industrial roof has usually not costed that.

Phasing around a working building

Almost every industrial refurbishment happens over an operating building, and the programme is shaped by that more than by the roof. Cut-edge treatment, fastener replacement and gutter lining are all bay-by-bay operations that keep the building weathertight throughout — nothing is opened up — so they sit comfortably alongside production with an exclusion zone below the working area.

Rooflight replacement is the exception: each opening is briefly open, so it is planned unit by unit with protection beneath and usually scheduled around shifts. Coating work is weather-dependent, since cold-applied systems have minimum application temperatures and cure times, which is why an industrial coating programme is normally held to the warmer months rather than squeezed into a winter window.

What you should expect in a programme is a bay sequence, the access strategy, the exclusion zones, the hours, and what happens if the weather goes against it. Those are the things that determine whether the job disrupts you, and none of them appear in a rate per square metre.

What industrial refurbishment costs

Refurbishment is priced by intervention rather than by a single roof rate, which is precisely why it is worth doing: you pay for the five defects you actually have rather than for a new roof. Full published ranges are on the cost page.

Targeted work — cut-edge treatment, fastener replacement, localised repair and overlay — sits in the £25–£70/m² band over the treated area, and on a roof where the defects are genuinely discrete the treated area may be a small fraction of the whole. A full cold-applied liquid coating across the roof runs in the £100–£180/m² range with guarantees commonly around 20–25 years. Gutter lining and rooflight replacement are priced as separate items and should appear as separate lines, not be buried in a rate.

Against that, an industrial roof managed reactively can absorb an indicative £6,000–£9,000 a year in call-outs that never resolve anything, before you count a single ingress over stock, plant or a production line. Refurbishment is usually the intervention that converts that recurring, unpredictable spend into one planned, guaranteed piece of work.

VAT is charged at the standard 20% (VAT Notice 708), recoverable as input tax by a VAT-registered business. Where insulation is added, it generally falls to the special-rate pool rather than the main pool, with the Annual Investment Allowance the usual practical route — confirm the treatment of your scheme with your accountant.

What to ask for in a refurbishment survey

A useful industrial survey reports on each of the five failure points separately, with photographs: the extent and severity of cut-edge corrosion, a sample assessment of fastener and washer condition, the age and fragility of the rooflights, the state of the lap seals, and the condition of every gutter run and outlet. It should say what it found about the liner and the purlins, and it should flag any asbestos finding.

What comes back should be an itemised proposal with a line for each intervention, so you can see what you are buying and defer anything you choose to defer. A single lump-sum figure for "roof refurbishment" cannot be compared with another one, cannot be value-engineered sensibly, and hides whether the gutters were priced at all.