I have an asbestos cement garage roof; What shall I do?

Interior Concrete Garage

First of all it is worth really checking it is a cement asbestos roof. It is very hard to tell the difference between asbestos fibre cement roof sheets and non-asbestos fibre cement roof sheets. Often we visit customers who have been told by qualified building surveyors or very experienced roofers/builders there is asbestos present when it turns out there is not. In our industry asbestos cement was widely used in roof sheets until about 1991 after which a good alternative to asbestos cement was found. It did not become illegal until 1999 but most garage manufacturers stopped using it around 1991. We have been working with Cement garage roofs since about 1971 and have long experience of both types. We would generally suggest getting the material sampled and tested if there is any doubt as to whether or not it contains asbestos. We can help and advise on this if you decide to get the removal and replacement done by us.

In the event that it is decided you have a cement asbestos roof there are a number of ways various companies may suggest you deal with it. In most cases the option they will suggest will be the one they prefer to offer you irrespective of what is the best option for you. The three main options are as follows:


We tend to recommend REMOVAL and REPLACEMENT of asbestos cement but we feel we should explain our reasoning behind this, which is as follows:


o The job is done once and the cement asbestos problem is gone
o It’s cheaper in the long run because you have done the job properly once and don’t need to worry about the cost of doing it again.
o There is a huge range of roofing materials to choose from.
o Long term safety: You don’t need to worry about the asbestos cement roof sheets any more.
o The alternatives may cause more damage to the old asbestos cement roof sheets. In our experience the roof may leak more after over-cladding or coating/painting than it did before the work was done.
o SPEED: As a result of really good planning and organization most of our asbestos cement roof sheet removal and replacement jobs are completed within one day so the disruption is kept to a minimum.


In the short term over-cladding or coating/painting may be cheaper, however they still leave you with asbestos cement sheets on your garage roof. This will still appear on a home report or survey of your property. This may leave you with a choice of getting the roof replaced properly before selling the property or selling at a reduced price to reflect the cost of the buyer having to do this. So you save money at the beginning but end up with the disturbance of doing the job twice and paying twice.


You may have concerns about the risks to you and to others due to the asbestos cement roof sheets. If the cement asbestos sheeting is in good condition (not leaking, not flaking, not cracked or showing any signs of damage) then you are probably not at a significant risk from it. On the other hand if the asbestos cement roof sheets are flaky or damaged or you feel some work needs done on them then we feel the right answer is to replace them. Remember that all cement asbestos sheets are now probably over 17 years old and will be showing signs of old age now or in the near future. Over cladding or coating/painting may not slow the ageing process down much and they will continue to deteriorate.


o The British standards code of practice for buildings and roofs in the west/central mainland Scotland require them to be designed and built to withstand wind gusts in excess of 100 miles per hour. In order to do this any over-cladding must have so many anchors/bolts/fixings down into the beams below the cement asbestos roof sheets that there will be a considerable amount of drilling of the existing asbestos cement roof sheets. This creates a risk since over-cladding contractors often say you don’t need to empty your garage and with all this drilling you may contaminate the contents with asbestos fibres. This is now more dangerous than before you had any work done.
o If not enough fixings are made down through the cement asbestos sheets then the next 100 mile an hour gust (Last two were Boxing day 1998 and 3rd January 2012) will see your over-clad roof come off with bits of the old cement asbestos roof spread across your garden (and possibly some of your neighbours’ gardens too).
o Over cladding is really just postponing the day you will need to tackle removal and replacement of the asbestos cement roof sheets.


Very often we are asked to look at cement asbestos roofs that have been coated or painted before. The problems reported are usually two fold:

o Although the roof leaked a bit less immediately after the coating was applied it is now leaking worse than before. This is usually because the coating has now flaked off in places allowing the water in below the coating but the rest of the coating is still fairly intact so the water can’t get out and works its way through the old cement asbestos sheets.

o Condensation in the winter can be a problem with any single skin roof in winter. Asbestos cement roof sheets are designed to be a wee bit porous allowing the sheets to breathe. This allows some damp air from inside the garage to get out through the sheets and reduce condensation. Once the sheets are coated or painted this cannot happen any more and an increase in condensation in the winter is inevitable. Many customers we speak to with old over painted cement asbestos roof sheets report this.


o Coating or painting is often described as a “safer” option. This is often not the case as in order to get the coating to stick the existing cement asbestos sheets need to be scraped to remove moss and thoroughly cleaned down. This very often produces a great deal of loose tiny asbestos fibres which, if they are not captured as they are produced can cause a bigger safety problem for you than any of the other options. This waste then needs proper disposal under the SEPA rules and will need notification to the Health and Safety Executive under the asbestos regulations.

We hope that this has been helpful and if you have any questions on any of the information given above please contact us on 01505 850501 or 0800 212023

We carry out garage roof removal and replacement throughout West/Central mainland Scotland. If you feel you would like a free site survey and quotation for your garage roof you can get in touch with us as follows:

Tel: 01505 850501
Freephone 0800 212023
E mail [email protected]

The information provided here reflects our opinions based on our experience over years of dealing with this type of roofing and feedback provided by customers who have had experience of over-cladding and coating/painting of cement asbestos roof sheets. For more information you are encouraged to look at the HSE web site at: http://www.hse.gov.uk/asbestos/essentials/

Copyright : D Welsh Builders. 1 Neilston Road, Uplawmoor, Glasgow. G78 4AB. October 2018.