A commercial roof repair is bought on downtime. The building has to keep trading, the leak is usually over something expensive, and the covering is a profiled metal sheet or a single ply membrane rather than anything a house would wear. The decision that matters is not who patches it but whether patching is the right answer at all for how long you need the building.
Where commercial roofs actually fail
Profiled metal roofs fail at the laps, at the fasteners and at the cut edges long before the sheet itself perforates, which is why a survey that reports on those three things tells you more than one that reports on the sheet. Single ply membranes fail at welds, at upstands and around penetrations that were added after the roof was laid. On both, the commonest cause of a new leak is somebody else's work: a cable tray, a condenser unit or a handrail bolted through a roof nobody made good afterwards.
Patch, coat, overlay or strip
Those are the four options and they buy different amounts of time. A repair buys a season and is right when the rest of the roof has years left. Cut edge corrosion treatment and a coating system can add a decade to a sheet whose corrosion is confined to edges and fixings, and is money spent twice on one that has perforated in the field. An overlay lays a new system over the old without stripping, which suits an occupied building. A strip and replace resets the clock and costs the most disruption.
Commercial roof replacement cost: what contractors publish
A few contractors publish a rate per square metre. Nationwide Industrial Roofing gives £90 to £180 per square metre to strip and replace an industrial roof, and Total Cladding and Roofing assumes £120 to £170. S Jones Roofing gives £60 to £120 per square metre for replacing a flat roof, before access. Size, scaffold, the existing covering and whether asbestos is present move every one of those figures.
Commercial roofing repair near me: ask for the plan for an occupied building
What separates a commercial roofing contractor from a domestic one is the plan for the hours the building is in use. That means working in bays, making each bay watertight before the end of the shift, out of hours and weekend working where the space below cannot be cleared, and a written answer to what happens if it rains at four o'clock. Ask for that plan in the quote, because it is the part that decides whether the repair costs you more in lost trading than in roofing.
Questions people ask about commercial roof repair
Commercial roof leak repair: how quickly can the water be stopped?
A temporary repair to stop water entering can usually be made on the first visit if access is available. The permanent repair waits on the survey, because the entry point on a large roof is often some distance from where the water appears inside.
What does a commercial roof coating cost compared with replacement?
Duratite gives a complete GacoFlex coating system from £40 per square metre fully installed, and a Gaco acrylic system on asbestos cement roofs from around £25 per square metre with a ten year warranty. That is well under the published replacement rates, and only worth it where the sheets are still sound.
Who is responsible for a commercial roof, the landlord or the tenant?
It depends on the lease, and on a full repairing and insuring lease it is commonly the tenant. Read the repairing obligation before commissioning work, because who pays and who instructs are not always the same party.
Does commercial roof work need building regulations approval?
Repairs generally do not. Replacing a substantial part of the covering, or changing the thermal element, is controlled work and needs either building control or a contractor registered on a competent person scheme.
Is a commercial roof installation on a new building priced the same way?
Broadly, by the square metre and the system, but without the strip out, the protection of a trading building below or the phasing in bays. Those are the costs that make work on an occupied building dearer than the same area of new roof.
Sources
- HSE: fragile roofs and roof lights
- Approved Document B: fire safety (GOV.UK)
- Nationwide Industrial Roofing: cost of industrial roof repairs
- Total Cladding and Roofing: commercial roof repair vs replacement
- S Jones Roofing: the cost of replacing a commercial roof
- Duratite: industrial roof waterproofing
- Duratite: asbestos roof waterproofing cost UK