Solar on asbestos roofs
Asbestos cement roofs are common on garages, outbuildings and farm buildings, and drilling into one is regulated work. It is not licensed work — but it is not ordinary work either, and an installer who treats it as ordinary is the problem.
Non-licensed does not mean unregulated.
HSE classifies work with asbestos cement as non-licensed — it does not require a licensed contractor. But the Control of Asbestos Regulations 2012 still apply, and the work needs trained people, a risk assessment and a plan of work. HSE publishes task-specific guidance for drilling into asbestos cement.
The bigger point is practical: you would be fixing a 25-year asset to a brittle covering that is probably near the end of its life. Replacing the roof first is usually the better answer.
Where you meet it
Asbestos cement roofing was widely used into the 1980s, and it is still common on:
- garages and outbuildings — corrugated sheet, often original to the building
- agricultural buildings — large spans on lightweight frames
- industrial and commercial units
- occasionally on house extensions and lean-tos
The material is a cement matrix with asbestos fibres bound into it. Intact and undisturbed it is relatively low risk, which is why the regulations treat it differently from friable insulation. Drilling, cutting or breaking it releases fibres, which is the point at which the framework engages.
What the work involves
It is non-licensed work. That is HSE’s classification for asbestos cement, and it means a licensed contractor is not required.
It still requires competence. Trained workers, a risk assessment, and a plan of work. HSE’s asbestos essentials series includes task-specific guidance for drilling holes in asbestos cement and other highly bonded materials, and separately for removal and dismantling.
An installer who shrugs at this is the risk. The correct response to “the garage roof is asbestos cement” is a set of questions about training and method, not “that’s fine, we drill through anything.”
How old is the roof, and what is your plan for it?
Asbestos cement roofs on domestic outbuildings are typically forty to sixty years old. Weathered sheet becomes brittle, and it is not a covering with decades left.
If the roof is coming off within the array’s life, fitting the array to it now means paying to remove and refit — and doing the asbestos work under time pressure rather than on your own schedule.
The alternatives, in rough order of sensibleness
1. Replace the covering first, then install. Removes the asbestos question, gives you a roof with a known life, and lets you consider an in-roof system. Most expensive up front and usually cheapest over the system’s life.
2. Use a different surface. The house roof, another outbuilding, or ground mounting if the plot allows — though Class B’s limits are tight: one array, 9 m² of panel, 5 m from every boundary.
3. Install on the asbestos roof with proper method. Done routinely on commercial and agricultural buildings by contractors who do this work. Requires the training, assessment and method above, plus a structural assessment of both the sheet and the frame.
4. Do nothing to it. Intact asbestos cement that is left alone is not an emergency. If solar is not urgent, leaving the roof undisturbed until it needs replacing is a legitimate choice.
Structure, separately
Two structural questions, not one.
The sheet itself. Brittle, degrading, and not designed to carry point loads. Walking on asbestos cement roofing is a well-known fall-through risk, quite apart from the fibre issue.
The frame beneath. Often lightweight — purlins sized for a light covering and nothing else. MIS 3002’s list of conditions requiring a structural engineer includes a roof type not covered by its standard methodologies and any showing signs of distress; an ageing asbestos cement roof on an agricultural frame is comfortably both. See structural surveys.
Questions for an installer
- Have you done asbestos cement roofs before, and what is your method?
- Who is trained, and to what standard?
- Will there be a written risk assessment and plan of work?
- Who has assessed the sheet and the structure beneath it?
- How will you avoid loading or walking on the sheet?
- What happens if a sheet breaks during installation?
- Have you priced replacing the covering instead, so I can compare?
The last one is the useful one. Very often the comparison changes the decision.
Sources
Contains public sector information licensed under the Open Government Licence v3.0.
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