UNITED KINGDOM Annual driving rain index

Durability against the elements is a key factor in determining the materials selection on a construction project.

Providing enhanced protection for the most vulnerable locations is why many architects and specifiers select Welsh Slate as their chosen material.

Generally any area within 30 miles of a west facing coastline is considered to be in a severe exposure area.
However, localised effects on any site must also be taken into consideration. Further reference to BS 8104 is advisable to ascertain localised effects. Map based on BS 5534.

 

Welsh Slate is the perfect natural product for harsh conditions

Welsh Slate is exceptionally durable. It is unaffected by normal extremes of temperature and is highly resistant to acids, alkalis and other chemicals. It retains its colour, even in UV light and is impermeable to water. Welsh Slate is non combustable and is compatible with all other building materials.

Water permeability - Impermeable

Sunlight unfading - Unaffected by UV light

Heat - Unaffected by normal heating, freezing and thermal cycling

Chemical resistance - Unaffected by atmospheric pollution, sea air and sea spray

Biological resistance - Unaffected by vegetable growth, rot or insect attack

Compatibility - Compatible with all building materials

Fire resistance - Slate is non combustible and does not support combustion. AA fire rating

Thermal expansion - 8.5 - 11x10-6 mm per 0C

Thermal conductivity - Approx. 2.0 W/mk

Less than 56.5 l/m2 per spell

Size (Nominal)

mm

Minimum Rafter Pitch

 


  20º 22.5º 25º 27.5º 30º 35º 40º 45º to 75º 85º

600 x 350

115*

105*

95*

85*

80*

70*

60*

55*

50*

600 x 300

-

-

95*

85*

80*

70*

60*

55*

50*

550 x 300

-

105*

95*

85*

80*

70*

60*

55*

50*

500 x 300

115*

105

95

85

80

70

60

55

50*

500 x 250

-

-

95

85

80

70

60

55

50

450 x 300

-

-

-

-

80

70

60

55

50

450 x 250

-

-

-

-

80

70

60

55

50

400 x 300

-

-

-

-

80

70

60

55

50

400 x 250

-

-

-

-

80

70

60

55

50

400 x 200

-

-

-

-

80

70

60

55

50

350 x 300

-

-

-

-

80

70

60

55

50

350 x 250

-

-

-

-

80

70

60

55

50

350 x 200

-

-

-

-

80

70

60

55

50

300 x 200

-

-

-

-

80

70

60

55

50

270 x 180

-

-

-

-

80

70

60

55

50

56.5 l/m2 or greater per spell

Size (Nomina,l)

Minimum Rafter Pitch

mm

20º

22.5º

25º

27.5º

30º

35º

40º

45º to 75º

85º


600 x 350

150*

130*

120*

110*

100*

85*

80*

70*

65*

600 x 300

-

-

120*

110*

100*

85*

80*

70*

65*

550 x 300

-

130*

120*

110*

100*

85*

80*

70*

65*

500 x 300

-

130*

120*

110*

100*

85*

80*

70*

65*

500 x 250

-

-

-

110*

100*

85*

80*

70*

65*

450 x 300

-

-

-

-

100*

85*

80*

70*

65*

450 x 250

-

-

-

-

100*

85

80

70

65

400 x 300

-

-

-

-

100*

85

80

70

65

400 x 250

-

-

-

-

100

85

80

70

65

400 x 200

-

-

-

-

100

85

80

70

65

350 x 300

-

-

-

-

100

85

80

70

65

350 x 250

-

-

-

-

100

85

80

70

65

350 x 200

-

-

-

-

100

85

80

70

65

300 x 200

-

-

-

-

100

85

80

70

65

270 x 180

-

-

-

-

100

85

80

70

65

 

 

 

Sales Office
Penrhyn Quarry
Bethesda
Bangor
Gwynedd
LL57 4YG

+44 (0) 1248 600656
enquiries@welshslate.com

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