Generally, they work by combining two or three layers of material together to make an impenetrable barrier that is then coated with a waterproof finishing material to further protect the substrate. Thermal insulation can be used to increase the UV rating of the building according to the new building regulations.
There are a number of reasons to use roofing felt, apart from the fact that it is a proven material that has been in use for many years. Firstly, the size of the job is immaterial – it can be large or small and the felt can cover it easily. Roofing felt is both durable and able to deal with the worse of the weather such as wind a rain. It can also be applied to both flat roofs and also pitched and curved roofs meaning there are many jobs where it is the perfect roofing material. There is also a range of different ways that it can be applied to the roof. Felts are a more robust material for heavy duty wear and tear.