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Should I over clad or coat my asbestos roof?

9 December 2015

Coating Vs. Over Cladding an Asbestos Roof

This is probably the biggest question that building owners face, and the decision involves budget, roof suitability, accessibility, waterproofing, and aesthetics. There's also some serious asbestos safety concerns to consider.

We all need a good roof over our heads, and getting a leak stopped quickly and effectively is essential in securing the long life of the structure of the entire building. Many firms will offer a one solution service, and try to fit all of a building's needs into their method, but a roof needs a personalised plan that's going to achieve maximum waterproofing with minimum cost and fuss. Here's our independent guide to over cladding vs. coating an asbestos roof.


Coating has traditionally been the cheaper method of waterproofing an asbestos roof, but a fluctuating steel price can change this, steel being the favoured material used in over cladding. As for how this will exactly affect the price differential between the two systems, no one can know for sure at this time.

Of course, it's not only about the price of the product. Both solutions need access to the roof via cherry pickers and scaffolding, adding labour and hire costs to the bill. But this is where coating clearly trumps over cladding. Coating a roof can be quicker and easier, meaning on site time is reduced and scaffolding isn't required for as long. There's also extra construction costs involved in over cladding, such as meeting current regulations for insulation, and ensuring the building structure is strong enough to support another roof.

With all that in mind, coating is almost always a more cost-effective solution to a leaking asbestos roof.

Roof Suitability

This is where the choice might be made for you. The most common issue is where a roof is so broken it's beyond coating, but then it may not be structurally sound enough to be over clad either.

With over cladding, you get a whole new roof, meaning you don't have to spend time and money repairing the old one. But first, a structural engineer will need to check if the roof will take the weight of new metal sheets. Many older ones won't be able to. Depending on your area, you may need planning permission and will have to meet certain building regulations, which complicate the project and could push the price up.

Roof cladding requires bolts to be pushed into not only the asbestos roof, but also the overall building structure. However, many asbestos roofs are built with concrete portals, meaning the roof is supported by a small number of concrete arches. This means the new roof cannot get enough stability on top of the old one, a common risk of over cladding.

A coating system is generally more versatile than over cladding and can be used on more roofs. It also does the job of securely encapsulating the asbestos fibres, whereas over cladding risks doing the opposite by drilling into the old roof, a controversial method that the HSE recommends against. This is enough to put many building owners off over cladding. When employees are spending a lot of time under this roof, the risks of asbestos inhalation are greater. This is the deal breaker for a lot of building owners, and many large businesses have turned to coatings to avoid this hazard. Nobody wants their employees' lungs to be at risk. There's also far less disruption involved with coating a roof, meaning a minimal break in business as usual.


Put simply, can a roofing contractor get up there and do what they need to do safely? This is where older buildings can prove a challenge. Is the roof safe to lay boards on and can a team of contractors confidently stand up there? A roof's condition will need to be investigated first.

Both over cladding and coating have the same needs when it comes to getting up on the roof, although, whereas over cladding involves lifting up many heavy metal sheets, coating requires carrying only the actual product and a few rollers or spray guns and hoses.

Safe accessibility is often a roofing professionals primary concern. If contractors can't safely access the roof and work on it then a repair is impossible. Other considerations include whether the ground around the building can support scaffolding or a cherry picker. Without good access, no work can be done with any solution.

Again, over cladding's drilling method prompts alarm bells. Breaking the surface of the asbestos is exactly what the HSE advise against, and over cladding involves doing this hundreds of times, often thousands, putting roofers and employees at risk. For this reason alone, coatings are a clear winner.

Aesthetics and Corrosion

Over cladding has typically trumped coatings here, as people like the look of a brand new roof. The shiny metal sheets straight from the factory give a feeling of strength, but with the advances coating technology has made, coatings looker sleeker and fresher than ever-- plus they're likely to stay that way far longer than an over clad. On top of this, coatings are often available in different colours, and will retain that shade for many years.

As metal sheets, an over clad is highly likely to develop rust and corrode from the inside, meaning ugly orange patches of rust start flaking off the edges of the roof. This is so frequent that some contractors make a living solely fixing cut edge corrosion, which can occur very quickly in a metal roof.

With long guarantees and an expectation of remaining effective for much longer, coatings come first again.


Over cladding provides a whole new barrier against the elements, giving the old roof a brand new lease of life.

Coatings are a highly reliable waterproofing method. If a penetration or leak were to occur, they're also reasonably easy to fix, with a further coating being applied on top. Spot repairs are easy to make and cost-effective. Repairing an over clad is often more complex-- you can't over clad an over clad...

It's worth remembering that buildings move all the time, particularly large-scale industrial ones such as in agriculture or logistics. Roof coatings are often specifically designed to have enough flexibility to adapt and shift with these movements.

With both over cladding and coating, you'll get instant waterproofing. But over cladding is again let down by its durability-- rust creeping in is difficult to stop, meaning a further leak is likely.



They've each got their merits, and a survey of the property would help decide which would be best. As always, it's up to the building as to how it gets treated. Roof cladding has some impressive aesthetics and good waterproofing abilities, and it remains a popular choice among building owners.

However, no matter who installs an over cladding, you've still got the problem of the holes being drilled into the old roof. This is the deal breaker for us, and why many roofers will only work with coatings. Disrupting the asbestos cement is the number one way to release harmful fibres, and that's not something we'd want for our customers or employees.

For us, the coatings solution wins out almost every time. Their versatility on different surfaces and incredible waterproofing abilities make them a worthy winner. It's also plain to see how its easy, fast and simple application mean it's fast becoming the building owners' favourite.


Got questions about over cladding or coating? Or want to clarify something with an expert? Call 0800 6120 750