Slate Roof Pitch Regulations

The headlap of the slate is adjusted according to the roof pitch.

Slate roof pitch regulations.

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 slope roof pitch r905 3 2. 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. This means for every 12 horizontal units the roof must rise a minimum of two and one half vertical units.

Higher exposure or different sized slates necessitated a greater roof pitch of 22 5 or more. 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. 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. Headlap as defined in the national slate association s slate roofs design and installation manual 2010 edition is the length in inches of the upper portion of a roofing slate that is covered by the butt of the slate two course above.

Where the thickness of natural slates reduces their pitch by 3 or more select the next lower rafter pitch to determine the recommended head lap and slate width. Clay and concrete roof tiles can only be installed on roof slopes of 2 1 2 12 or greater. The roof pitch should be at least 20 which is influenced by the length head lap and thickness of the slate. Minimum fixing on double lap slates.