You can also calculate roof pitch even without using a roof slope calculator.
Slate roof pitch.
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.
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.
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.
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.
Conventional roofs are the easiest to construct and you can walk on them safely.
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.
At that point measure down from the exposed butt end back to the roof surface.
Minimum roof pitch for shingles.
It is agreed that the roof pitch should be a minimum of 20 degrees preferably a bit more.
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.
High pitched roofs often need extra fasteners and their pitch can be as high as 21 12.
Generally a slate roof is not installed on a pitch less than 4 12.
As per the nrca roofing and waterproofing manual fifth edition they recommend that roof deck slopes intended for the application of steep slope materials at 4 12 18 degrees or greater.
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.
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.
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.
Higher exposure or different sized slates necessitated a greater roof pitch of 22 5 or more.
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.
The slope of a roof is often referred to as the roof s pitch.
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.
Page 405 roof slope.
When slating with a shallow pitch a wide slate is highly recommended for maximum side lap or lateral lap side overlaps.
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.
