Natural slate

Design considerations for the installation process of a natural slate roof

natural slate roof

Natural Slate is a suitable choice for new build, residential and commercial projects.

Slate is a timeless classic, also regularly specified throughout the UK for projects within conservation areas, national parks, heritage sites and areas of outstanding natural beauty as an acceptable replacement to indigenous slate as it has a very similar composition and is of comparable quality.

The installation of a slate roof involves a number of aspects that must be considered in the design process.

Most significant is the environment, with the two main factors being exposure to wind and rain. The primary aspects to be considered are:

uk zones rain exposure


Buildings positioned on slopes, hills or coastal areas as well as tall buildings will be graded with higher exposure.


Small slates are more suitable for steep roofs, while the more exposed the site and on lower roof pitches, wider slates should be used and the lap increased.


This is established by measuring the roof pitch and considering the rain and wind exposure. BS5534:2003 gives guidance on the exposure of a given site.

Where the thickness of natural slates reduces their pitch by 3º or more, the next lower rafter pitch should be selected to determine the recommended head-lap.


When considering the minimum pitch for a slated roof it is necessary to establish the exposure of the site, the length of rafter and the height of the building.

The recommendations shown above are based on a maximum height to eave of 12m and a maximum rafter length of 9m in moderate exposure and 6m in severe exposure.

In general any area within 30 miles of a west facing coastline is considered to be one of severe exposure:

Pitch of roof

CUPA PIZARRAS takes quality control and testing very seriously and has rigorous systems in place to ensure that each slate meets or exceeds internationally recognised standards of excellence.

The company’s unique barcode technology lists the quality, composition and source of each slate, from quarry to installation, enabling unequalled traceability and future matching.

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