This means for every 12 horizontal units the roof must rise a minimum of 4 vertical units.
Minimum angle for slate roof.
Generally speaking 20degrees 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.
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.
You consider some alternative solutions.
It is agreed that the roof pitch should be a minimum of 20 degrees preferably a bit more.
Roof pitch refers to the measurement of the slope of a roof and you express this as a ratio.
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.
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.
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.
Higher exposure or different sized slates necessitated a greater roof pitch of 22 5 or more.
There is no maximum pitch up to 90 degrees.
Slate shingles can only be installed on roof slopes of 4 12 or greater 33 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.
Although there s isn t any standard pitch of a roof used on all kinds of sloped roofs you can determine the range of pitches by using a roof angle calculator and by considering factors like the local climate and roofing materials.
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.