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It is commonly asked which flat roof system is the best. The answer to his is it depends on the roof. All flat roof systems have their own strengths and weaknesses. This includes both weaknesses during and after the installation process.
Below we look at the strengths and weaknesses of several flat roofing systems.
Liquid roofing systems provide nearly everything you could want in a flat roof system. They are easy to install, can be applied at a range of temperatures. And provide a seamless finish. The fact the system is liquid also makes it perfect for complex detailing around soil vent pipes, plant machinery and sky lights.
Drawbacks of liquid roofing systems include the low barrier of entry for installers, the thickness of the coating and the need to install the system when it is dry. Some liquid system providers offer 1 to 2 day courses to become an accredited installer1. The obvious problem with this is no time is taken to become a skilled tradesman. The way around this is to ensure you contract a professional roofing company for any liquid roofing installations. The thickness of liquid coating can make it prone to impact fractures which other systems would have the ability to cope with. Also, the substrate can poke through the liquid coating meaning you are not left with a smooth finish. Finally, weather conditions in months with a lot of rainfall can lead to a lot of disruption as conditions need to be dry for installation.
Mastic asphalt has been used for waterproofing for more than a century. During this time, it has become known in the construction industry as “The King of Waterproofing”. There have hardly been any changes made to the system over this period aside from the addition of advanced polymers to further enhances its performance. It is a carbon zero rated product, providing a seamless finish and can form to almost any detail. Additionally, mastic asphalt installation is carried out by asphalt spreaders who have carried out a long apprenticeship. This means you can have a high degree of confidence the installation will be of the highest quality. You can be even more certain of quality workmanship if the company carrying out the installation is accredited by the Mastic Asphalt Council2. Another positive of mastic asphalt is any repair work needed is straightforward. In fact, nearly all problems with a mastic asphalt flat roof will just need repairs not a flat roof replacement.
The drawbacks of mastic asphalt are it is one of the more expensive flat roof systems and that it does require a coat of solar reflective paint every 5-10 years. This is because it is susceptible to thermal movement. And movement around the lead flashings.
Rubber roofing often referred to as a single ply is a membrane which can be both glued or mechanically bonded to the substrate. If it is mechanically bonded to the substrate the laps will be glued or heat bonded. A big advantage of rubber roofing systems is large areas can be installed in a single day. Additionally, it can be installed flame-free.
The disadvantages of a rubber roofing system are than it is prone to some faults. These faults are shrinkage and the fact it is a single membrane. The problem with a single membrane is it can easily be punctured. If this happens it is likely the roof will suffer from water ingress.
Lead roofing has been used for many centuries. It can be seen on many period building, churches and cathedrals. Lead is unparalleled when it comes to longevity with the capability of lasting 500 years. It is also 100% recyclable. And provides a very decorative finish.
Lead does not have any real downsides in terms of performance. However, it is a very expensive roofing system. And unfortunately, criminals often target lead roofs for theft3.
Fibreglass flat roofs often also called GRP roofing has become one of the UK’s most popular roofing systems. It is a rigid roofing system which is resin bonded with chop stranded matting (CSM). This chop stranded matting goes between 2- layers of resin coating. A benefit of this system is it can be finished in almost any colour and is very robust.
However, the are some common fibreglass roof problems. These range from poor installation where you see problems such as cracking and pinholes. And difficulties laying a GRP system in winter months due to difficulties in keep boards dry (also this roof system normally needs to be laid on OSB board). Through to expansion joints being needed for every 60 square metres of roof.
Torch-on felt or reinforced bituminous membrane roofing (RBM) is an extremely popular roofing system. It can be used as a both a single and double membrane. It is laid in rolls with laps showing a ‘bitumen bleed on joints. Torch-on felt can be a variety of thicknesses up to 5mm allowing it to cope with thermal movement. Both SBS and APP bitumen can be used to suit the situation.
A downside of felt is it is not a self-terminating system. This is a problem when it comes to repairs as the whole area will need to be removed and replaced. Torch-on-felt roofing systems which do not make use of a separating flashing or termination bar are also prone to problems with thermal movement.
As stated in the introduction there is no best roof system. It depends upon the roof in question. The greatest variable in the quality of a roofing system is the quality of the installation. First, find a professional roofing company with a proven track record then find the right system for your project. This will ensure you have the best flat roof system for your needs.
If you would like any help or a quotation regarding a flat roofing system please get in touch with us or call us now on 01277 375 511. One of our friendly team of flat roofing experts will be happy to help you.None None