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How Long do Roof Coatings Last?

Updated on October 24, 2012

Over the last 6 years I have witnessed a dramatic increase in the number of homeowners choosing to have their roof tiles cleaned and coated with a waterproof colourant.

I will briefly explain the process that is typically used:

  1. Roof tiles are pressure washed and then allowed to dry
  2. Moss killing fungicide is applied to the tiles to prevent early regrowth
  3. Tiles are coated with a waterproof sealant that also contains a colourant
  4. Cement, lead and bricks on chimneys are often coated as well

As a traditional roofing contractor I have always been skeptical about how long the coating will remain on the roof and also about the benefits that many manufacturers and companies claim.

I have personally seen over 100 roofs coated and resealed and to be honest I am not impressed with the longevity of the product.

Worse still, many companies that apply these coatings seem to dissolve and reappear as a new business trading under a different name. I can only assume that this is because the roof coatings do not last very long and the companies cannot survive financially if they were to honour the guarantees they previously supplied to their customers.

I know that this is a bold statement to make but as I drive around my local area I see more and more roofs that have been recoloured yet, a couple of years later the coating seems to peel or flake off.

Suspicious Claims

Many of these roof coating companies employ door canvassers to sell their products or use leaflets that make suspicious claims about the product.

Here are a few claims that I would be very wary of:

  • Increases value of the property
  • Stops all roof leaks
  • Reduces heating bills by (insert high number here) percent
  • Stops moss growing on the roof
  • Increases the life of the roof
  • Environmentally friendly

I can say that in my opinion all of these claims are bogus, here's why:

1) Increases value of the house

This isn't true, I have already spoken to several estate agents in my area and every one of them has told me that applying a roof coating will not affect the value of the property. Would you pay more for a property because the roof had been painted red? I wouldn't!

2) Stops all Roof Leaks

Tiles break for various reasons, sometimes because they have an existing hairline crack, sometimes due to a mistake in production. Roofs also leak because of faulty lead, chimney issues and problems with the cement.

Applying a thin coating may protect the tiles from weathering for a few years until the product itself wears off but it isn't a magic bullet that will prevent all future roof leaks. Yet that is how some people market this product.

3) Reduces Heating Bills

Most roofs in the United Kingdom are designed to allow the area beneath the tiles to breath, this prevents condensation in the loft which can rapidly lead to mould and rot..

To improve the thermal efficiency of a home, one should focus on insulation placed just above the ceiling and in the cavity wall.

The thermal properties of roof coatings are very very small, using them to insulate a vented "cold" loft is utterly pointless and a waste of money.

4) Prevents Moss Growing on the Roof

The moss killing chemical mixed with the roof coating will wash off with the rain and moss will grow on the roof tiles after a couple of years. Rather than paying for a roof coating, it would be much much cheaper to scrape the moss from the roof and use a moss treatment chemical such as this. Even if reapplied every few years, it would be much cheaper than applying a pointless roof coating.

Here is a photo of a roof that was coated a few years ago, it is now covered in moss growth:

5) Increases life of the Roof

Using a pressure washer can strip the granular surface of the tile, thus shortening the life expectancy of the roof.

Roof coatings do prevent weathering of the tile, but only for a short period time. Then the coating needs to be re applied or it will wear off.

Herefordshire County Council had this to say about Roof Coatings:

Cold calling for roof coating services is one of the biggest scams to have swept the UK in recent years. Moss does not damage your roof and should never be washed off in this way. Painting the tiles serves no useful purpose whatsoever and the whole process is simply unnecessary work.

You can read the more from official goverment sources on this Roof Coating Website

6) Environmentally Friendly

Many companies claim that a coating of paint is as good as a new roof and because you are not removing and disposing of old tiles there is a benefit to the environment.

The problem is these coatings do not make a difference to the life expectancy of the roof and the whole procedure is not comparable to a new roof which should last 80 - 100 years minimum.

The roof coatings I have seen appear to show serious wear and tear after only a few years and complete failure certainly within ten years.

Why would you want to pay for a new coating every ten years when it would be much cheaper to renew the roof every 100 years?


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