Can you overclad an asbestos cement roof deck?

In many cases, yes you can cement roof decking. Overcladding, which means installing a new roof over the existing one, can be a practical way to deal with an ageing asbestos cement roof without the cost and disruption of a full strip and disposal. It can improve weather performance and thermal efficiency, and it avoids disturbing the existing sheets where leaving them undisturbed is the safer route.

But it is never automatic, and it should never be treated as a default. There are two things that must be confirmed first.

First: can the metal roof overcladding structure take it?

Overcladding adds load to the existing roof and its supporting structure. Before any overclad is specified, the existing structure has to be assessed to confirm it can carry the additional weight of the new deck, insulation and finishes. This is a structural question for the project engineer, and it is not one to assume your way past.

Second: the asbestos itself

Asbestos cement is a regulated material, and any work that could disturb it falls under the Control of Asbestos Regulations 2012. Before refurbishment work, a refurbishment and demolition survey is needed to confirm exactly what is present and what condition it is in.

Work on asbestos cement that is in reasonable condition and is not being broken up is normally classed as non-licensed work, but that does not make it informal. It still needs a risk assessment, the correct controls, and trained, competent people carrying it out. Where the survey or the condition of the material demands it, a licensed asbestos contractor must be brought in.

The guiding principle is simple: nobody cuts, drills or fixes anything until both the asbestos position and the structural capacity are confirmed.

How RMD can help with metal roof overcladding

We supply and design roof decking for overcladding projects across the UK, and we work alongside your structural engineer and asbestos specialists rather than around them. We help with profile selection, layout drawings and delivery timed to your programme, once the structural and asbestos positions are clear.

If you are weighing up an overclad, talk to us early. We will help you work through what needs checking and get the roof deck side of it right.

Learn more about our roof supply and design service, or get in touch.