Roof Pitch Angle Building Regs

Flat roof drainage.

Roof pitch angle building regs.

Modern tiles permit shallow pitch but some of the older traditional coverings such as hand made clay tiles require quite steep slopes to ensure rain does not penetrate the roof covering. With regards to the pitch the building standard code bs 5534 recommends a minimum pitch of 200 for slate roofs. Traditionally a minimum roof pitch of 20 was recommended in bs 5534 but modern tiles and slates have now been designed for applications as low as 15. But since there is still a wide variety of slate roofing systems there are occasions when the minimum pitch can go down to as low as 15 0 depending on the uniqueness of the roof.

The angle of the pitch may be dictated by aesthetic or structural factors. On blue prints architects engineers usually display the pitch of a roof in the format shown on the image where number 4 represents a rise and number 12 represents a length. A sprocket is an additional piece of angled timber fixed to the main rafter at eaves level in order to change the pitch. If a thatched roof is constructed with gables without hips valleys or dormer windows it must have a pitch of 45 degrees and a clear span that is no more than 6 m.

It may also be influenced by the nature of the roof covering. A correctly build flat roof will drain the rainwater quickly and effectively into the gutters without allowing water to collect in depressions and pond on the surface of the roof leading to the build up of silt deposits on the roof and stresses in the membrane when the water freezes a small amount of ponding is inevitable and it should not reduce the. To help stop the rain going under the tiles you would increase the headlap of the tile to 100mm 75mm is standard it s also worth bearing in mind that the pitch angle of the roof tiles will be a couple of degrees less than the pitch of the rafters in the case of the marley wessex i think it s about 3 degrees less. Flat roof this usually consists of felting which has a slight fall to allow rain water to drain off.

Spacing must be done according to sans 10407. Squaring building lines example the picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7. This means if a roof rises 4 in the length of 12 your roof pitch would be 4 12 or 18 43 degrees. Yet another technique is to add sprockets.

It is uncommon to find a roof below 15 but for those very low pitch applications there are interlocking clay pantiles available suitable for use down to 12 5. Minimum roof pitch for shingles. That way you end up with a catslide a roof with one side longer than the other continuing at the same pitch over the two sides of the building. Pitch roof this is where tiles or slates are used and a void is usually created underneath.