Slate Roof Minimum Slope

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.

Slate roof minimum slope.

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. You need to consider the slope requirements of each panel to determine this minimum slope. It is agreed that the roof pitch should be a minimum of 20 degrees preferably a bit more. Slate shingles can only be installed on roof slopes of 4 12 or greater 33 slope.

It takes the manufacturer s recommendations the unique conditions of the roof as well as the skills and the expertise of the installer to arrive at the right slope. For standing seam metal roof panel systems a 1 4 12 minimum roof slope is prescribed. The profile is the shape taken by the sheets when you bend them to form panels. The minimum slope of a roof depends on the roof s profile.

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. The minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems. Slate shingles minimum roof slope roof pitch r905 6 2. Generally a slate roof is not installed on a pitch less than 4 12.

Wood shingles minimum roof slope roof pitch r905 7 2. The following table provides the minimum required allowable roof slope for each type of roofing material mentioned in the code. You consider some alternative solutions. Anything above a 8 12 is preferred and slopes in the 12 12 to 18 12 range are probably ideal.

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. This means for every 12 horizontal units the roof must rise a minimum of 4 vertical units. Generally the steeper the roof the better with regard to service life of slate. 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.

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. For metal panel roof systems with nonsoldered seams with applied lap sealant ibc 2018 prescribes a 1 2 12 minimum roof slope. Express the slope of a metal roof by a ratio which indicates the pitch of the roof. This 1 4 12 minimum roof slope requirement also applies to spray polyurethane foam spf roof systems in new construction.