Most houses in the UK are built with pitched roofs. Pitched roof are the best option simply because of our weather patterns – rainwater runs off an angled (or pitched) roof more efficiently.
However, the angle of the pitch that is used depends on a number of practical considerations.
The choice depends on what sort of useful space you want to have in the roof. If you are designing a house with a cold roof (ie one that is primarily used for storage rather than living space) then you will probably want enough space to accommodate a cold water tank and any storage. You will also want to design sufficient headroom to move about comfortably in the loft – so about six foot in the centre.
The result of these considerations is that the normal pitch of the roof on a domestic property is between 300 and 450.
Lower pitches tend to be used more commonly on extensions. A single storey extension on the side or rear of the house may need to have a lower pitch in order to avoid interference with first-floor windows.
In this case, householders will tend to choose a roof tile that matches the tile on the main roof of the house – but this may cause a problem as not all roof tiles are suitable to use for shallow pitches.
Any given roof tile has a minimum pitch at which it is effective at keeping the rain out. If you try to use them below the minimum pitch they will not keep out the driving rain. Correctly installed plain tiles, for example, will provide a totally waterproof pitch at 350 and upwards.
To get the same degree of weathertightness at a lower pitch you should be looking at large format tiles or interlocking large format tiles which can accommodate a pitch as low as 220.
In any pitched roof design you should check that the tile you are proposing to use is designed for that specific pitch – your roofing contractor will be able to advise you on all the technical performance issues relating to individual tile products.
