Surface Characteristics: a smooth, fine grained slate of uniform, unfading Blue/Grey or Heather Blue Colour which may on occasions contain slight surface intrusions.
Standard: Roofing slates exceed the requirements of BS 680:Parts 1 (1944) and 2 (1971).
Water Absorption: less than 0.23%(Blue/Grey) : 0.16% (Heather Blue).
Wetting and Drying: unaffected after 15 cycles.
Chemical Resistance: unaffected after 10 days in 20% sulphuric acid solution. Slates are resistant to severe atmospheric pollution, acid rain, sea air and salt spray.
Density: 2700 kg/m3
Weight: typically, 20"x10" slates fixed with a 75mm head lap weigh 27.2kg/m2
Carbonaceous Carbon: 0.18 wt%(Blue/Grey) : 0.05 wt%(Heather Blue).
Heat: slates are non-combustible and are unaffected by the normal extremes of temperature.
Sunlight: unaffected by UV light.
Biological: unaffected by moss and lichen growth, rot or by insect attack
Fixing: the roof should be properly marked out prior to any slates being fixed and all slating work should be in accordance with the latest editions of BS 5534 and BS 8000: Part 6. Natural slate is split by hand and individually dressed and should be treated as an individual unit when being fixed on the roof. One slate may suit a particular location on the roof better than another - perhaps for reasons of thickness, natural curvature, surface texture or appearance.