London 020 3904 9933 
We are receiving more and more calls regarding leaking rear extension pitched roofs. 
Many builders do not understand that certain products do not work when installed on low pitched roofs. 
Most slates and tiles do not work at low angles and the only thing that stops leaks is the felt under the tiles.  
Slates and tiles that are fitted below the angle they are designed to work will allow water ingress through cappilary reaction. This is where water is sucked up between the slates and tiles and then drips on the felt below. This water then collects normally at the eaves and over a period of time the felt will rot causing water ingress into the building. 
There are certain products that can be installed as low as 12.5 degees for tiles and as low as 15 degrees for slates, anything lower than this we would recommend a built up felt system as the best alternative. 
If you are thinking of building an extension or are having problems with a leaking extension please contact us for advise and a free estimate 
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