Slate Roof Pitch

In order to provide you with the opportunity to specify low pitched slate roofs below 20 with confidence siga commissioned the bre to carry out a set of tests.

Slate roof pitch.

It is agreed that the roof pitch should be a minimum of 20 degrees preferably a bit more. You consider some alternative solutions. A couple of likely slate suppliers are consulted and they confirm that they are happy to supply 600x300mm slates for a minimum roof pitch of 20 degrees assuming a minimum lap of 125mm. Generally a slate roof is not installed on a pitch less than 4 12.

They have a pitch ranging from 4 12 to 9 12. Higher exposure or different sized slates necessitated a greater roof pitch of 22 5 or more. With regards to the pitch the building standard code bs 5534 recommends a minimum pitch of 200 for slate roofs. These roofs have a pitch less than 4 12.

For example if the level is 4 above the roof at a point 12 away from where the level is touching the surface then the pitch is 4 12. On the roof hold the level perfectly level and measure the height from the roof to the level 12 inches away from where the level touches the surface this will be the rise. The tools required will be a contractor s level at least 24 inches long and a tape measure. Place the butt end of the level against the edge of the roof and extend it into the air balancing it until it becomes level.

Conventional roofs are the easiest to construct and you can walk on them safely. When slating with a shallow pitch a wide slate is highly recommended for maximum side lap or lateral lap side overlaps. Minimum roof pitch for shingles. You can also calculate roof pitch even without using a roof slope calculator.

High pitched roofs often need extra fasteners and their pitch can be as high as 21 12. Conventional low pitch slate roofs are recommended down to a minimum of 20 in areas of sheltered or moderate exposure providing a 500x300mm slate is used and a headlap of 115mm. 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. 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.

Generally speaking 20 degrees is the lowest advisable pitch for a slate roof depending on the size of the slates and how much that the roof is exposed to moderate weather conditions. Page 405 roof slope. Although bs 5534 recommends a minimum pitch of 20 ssq has developed a successful slate roofing system that allows the roof s pitch to be reduced to 17 5 generally and under some circumstances as low as 15 in areas considered to be unexposed. At that point measure down from the exposed butt end back to the roof surface.