Asbestos cement roof on a commercial unit: options

Before an option is chosen, three things need to be known. The first is whether the sheets really are asbestos cement. They often look it, with their grey, weathered, moss-stained corrugations, but a sample sent to a laboratory is the only proof. The second is condition: whole and weathered, cracked, holed or broken. The third is whether they are fragile. Asbestos cement sheets and the old rooflights set into them lose strength with age and can give way under a person, so nobody should step on them without proper crawling boards, platforms and edge protection.

Our commercial roof survey covers the condition, and the photographs show the extent of any damage. The survey is the point at which options become practical, because a plan built on a guess about the sheets has to be redone when the sample comes back. Leaving a sound, unbroken roof alone while you plan is often the safest interim step, and anything that disturbs the surface waits for the plan.

Encapsulation means sealing the sheets with a coating, so that fibres stay locked in and the surface is weatherproofed. It is aimed at sheets that are broadly sound: a few hairline cracks and surface weathering, but no widespread breakage. The roof is cleaned first, moss and loose material are treated, and the coating is applied as a system. Cleaning has to be done in a way that does not abrade the surface or spread debris, and pressure washing is generally avoided for that reason.

The advantage is that the sheets stay where they are, so nothing is broken up and there is no waste to dispose of. The drawbacks are that the asbestos remains in the building, and under regulation 4 of the Control of Asbestos Regulations 2012 the dutyholder for non-domestic premises must keep a register of where it is and its condition, with a written plan for managing it, and the coating will need to be inspected and renewed. Encapsulation does not strengthen a sheet, so fragility remains. It suits a building with a limited remaining life, or one where the owner wants to defer a larger spend, and it needs a survey to confirm the sheets will bear the work. Our page on liquid coatings on commercial roofs covers coatings more generally.

Overcladding fixes a new weathering layer, usually insulated metal sheet or composite panels, above the existing sheets. The asbestos cement stays in place beneath, undisturbed, and the new layer becomes the roof. For an industrial unit this has a clear attraction: the building stays in use, the asbestos is not broken up and the roof can gain insulation. Fixings pass through the old sheets into the purlins, and drilling needs control to avoid creating dust.

Overcladding does have limits. The structure has to carry the extra weight, which is a matter for a structural check. The building's Part L position also needs looking at, since a significant roof renovation can bring in insulation upgrades. The asbestos stays in the building, so it still needs recording, and anyone who later strips the new roof will meet it again. Rooflights and gutters also need thought, because the new layer sits higher. See our guide to metal roof sheets for commercial units for the cladding side, and industrial rooflight replacement for the openings.

Removal takes the problem out of the building. Under HSE's non-licensed work guidance, roof sheeting in asbestos cement is covered where it comes off carefully, without being broken up, and weathering alone does not change that. If the sheets are substantially damaged, or the method would shatter them and throw dust and debris into the air, the notifiable category applies. The employer then notifies the enforcing authority first, keeps health records and arranges medical examinations. The detail is on HSE's non-licensed work page.

We set out what the guidance requires for your particular roof once the sample result and survey are in. Removed sheets are bagged or wrapped and taken to a suitable disposal site.

MyBuilder's 2026 guide gives asbestos removal as averaging about £2,000, with a rate starting at £50 per m², and single garage roofs at £350 to £1,295. A commercial roof is a different scale, and price depends on area, height, access, sheet condition and disposal, which is why the quote comes only after the survey.

The right option comes from four questions. Is the building staying, and for how long? Are the sheets sound? Can the structure take a new roof? And can the business tolerate disruption? A short-life shed with sound sheets might be encapsulated. A unit with good purlins that needs insulation is a candidate for overcladding. A roof in poor condition, or a building due for redevelopment, points to removal.

If the business trades beneath, our page on repairing a commercial roof while you trade explains how a live site is protected. Gutters on these roofs are often asbestos cement or fixed to it, so our guide to box gutter leaks and linings may also apply.

For any option, the survey is followed by a quote on paper, and our workmanship guarantee runs for 10 years, in writing. See commercial roofing for the wider service.