Specifying Slate for a Roof: Key Design Points


If you want to design a slate roof that is both breath-taking and will perform well for generations to come, there are some essential things you need to think about.

Our technical experts are there to help you every step of the way so that YOUR DESIGN gets the most out of the roofing slate. You can contact our experts today and get your questions answered.

They’re on hand to help you whether you’ve got specific questions about a complex roof design or you’d just like a second opinion on common considerations like:

  • The calculation of the overlap needed – this is critical to the long-term optimum performance of the roof.
  • Inter-related factors including site exposure, roof pitch, slate type selected as well as the slate overlap.

Our technical team specialise in providing solutions to every issue you might face when designing a slate roof, so get your question answered today.

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Key considerations when designing a slate roof include:

  • Roof pitch – In general, the lower the pitch of the roof, the greater the overlap for the slate tiles laid on it. A longer lap will help resist capillary action. Smaller slates can be used on steeper roofs with free-flowing drainage. Exposed sites call for a wider slate with a greater overlap.
  • Environmental conditions – Local factors include high buildings, or structures on the slopes or the tops of hills and along the coast. Any increase in the exposure grading for the site will influence wind uplift considerations. A longer lap will help resist wind uplift.
  • Weathering – The degree of exposure to driving rain that the building will experience over its lifetime will influence the minimum lap of tiles to be specified.
  • Fixing – All SSQ natural slates can be fixed by using either traditional holing and nailing, or a hook fixing system.
  • Sorting – On site, ensure that the slates are sorted by thickness on the ground. See that slates of equal thickness are laid in any one course, with the thicker end at the tail. Thicker slates should be used in lower courses and thinner slates in upper courses
  • Construction – The rule of thumb for a natural slate roof is to have timber battens of 50x24mm, set out horizontally and nailed at 600mm centres. Underlay to BS 5534 part 1 is needed; use Type 1F reinforced bitumen felt or other approved material if the underlay is not fully supported. Provide a 10mm continuous vent at both eaves for a cold roof (insulation at ceiling level) construction, and 25mm for a warm roof (insulation in the plane of the roof). A warm roof will also need additional ventilation at or near the ridge equivalent.

Sourced from established quarries, a properly specified SSQ Ultra slate roof will provide your project with a service life in excess of 100 years, whatever local weather and environmental conditions prevail.

There are too many roofs out there that are not specified and installed in the correct manner. Make sure your roof lives up to its expectations by getting in touch. Ask our technical experts your question here and they’ll get back to you immediately.

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