The Mad Surveyor

Asbestos slates or asbestos tiles are not manufactured anymore for obvious reasons. Health.

But there are literally thousands of homes that have asbestos slates. Asbestos slates were used in abundance in the early part of the 20th century before health concerns were raised using asbestos.

I often get to see an asbestos slate roof and saw another one only yesterday. Most asbestos slate roofs that were installed 70 or more years ago are reaching the end of their useful life. Some asbestos roofs however, typically in more sheltered parts, are still going strong and good for many years to come yet.

Typically what happens is that the asbestos slate will start to become porous though actually not that leaky. The surface of the asbestos starts to rough up and the tips of the asbestos tile start to curl. More often than not the asbestos tile also has an abundance of moss growing on it and has been typically laid in a "diamond" fashion. When the asbestos slate starts to shale (break up in layers) then there is no hope but a new roof. Also, the curling will allow more wind blown rain to blow up into the loft space as at the time these asbestos tiles were laid using a felt protective membrane was a thing of the future to come. The other thing to notice about asbestos tiles is that from inside the loft you will often see water staining like a salt stain on the underside of the tile indicating that water is getting through. Not nice to see water coming into your loft, is it?

Is polyurethane spray foam the answer to a 70 years plus asbestos roof that is showing signs of curling and shaling? No! The reason is simple, polyurethane foam is sprayed from the inside but the major deterioration of the asbestos tile is happening on the outside. Once the asbestos tile starts to rough up and loose its protective surface the tile is on its way out to the tile knacker’s yard in the sky. It becomes porous and will not provide a long term suitable partner to the polyurethane foam.

The job I saw yesterday was a new roof job and not a polyurethane foam job. We as a company also have a professional reproofing team that are kept busy year round doing new roofs. I concluded that this asbestos roof was doomed after just 2 minutes of surveying.

Interestingly, my quote for a new roof was less than one polyurethane foam company had actually quoted to spray in polyurethane foam! As a rule, polyurethane foam installation is less to install by a good third to one half the cost of a relayed roof and has the additional benefits of minimal disruption, excellent insulation and roof bonding. It beggars belief that they should have even quoted for polyurethane foam never mind that they were also trying to charge a King’s ransom for a wrongly specified job! See my previous comments on the going rate price for polyurethane foam!