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.
Minimum degree for slate roof.
Generally a slate roof is not installed on a pitch less than 4 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.
The 30 degree 7 12 roof recommendation is backed up by testing according to the publication science daily.
The minimum recommended pitch for a natural slate roof is 20 degrees under sheltered or.
With regards to the pitch the building standard code bs 5534 recommends a minimum pitch of 200 for slate roofs.
The slope of a roof is often referred to as the roof s pitch.
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.
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.
Steeper slopes increase the sail effect that makes them susceptible to wind.
Higher exposure or different sized slates necessitated a greater roof pitch of 22 5 or more.
Lower slopes don t handle wind driven rain as well.
The result of your conversation is as follows.
It is agreed that the roof pitch should be a minimum of 20 degrees preferably a bit more.
It lasts up to 400 years as a roofing material.
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.
Roof slope equivalents as rise.
Minimum required headlaps and offsets should not be compromised.
There are some manufacturers that can go slightly lower such as the siga 56m natural slate which can go down to 20 in some instances if used with slate hook systems.
Degrees to pitch rise in run table.
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 page 405.
Run in degrees and as percentage the minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems.
Considerations must be given to the extent to which water will migrate under the slate shingles.
The following table provides the minimum required.
In slate roofing water.
A 30 degree roof slope 7 12 pitch is the right pitch to aerodynamically handle high wind.
