UNITED KINGDOM Annual driving rain index & HEADLAP TABLES TO BS 5534

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.

Less than 56.5 l/m2 per spell

 

Minimum Rafter Pitch

20

22.5

25

27.5

30

35

40

45 to 75

85+

Slate Size                     

600x350

 

115 *

105 *

95 *

85 *

80 *

70 *

60 *

55 *

45 *

600x300

 

190 *

130 *

95 *

85 *

80 *

70 *

60 *

55 *

45 *

                     

550x300

 

135 *

105 *

95 *

85 *

80 *

70 *

60 *

55 *

45 *

                     

500x300

 

115 *

105 *

95 *

85 *

80 *

70 *

60 *

55 *

45 *

500x250

 

 

125 *

95 *

85 *

80 *

70 *

60 *

55 *

45 *

                     

455x250

 

 

105 *

95 *

85 *

80 *

70 *

60 *

55 *

45 *

                     

400x250

 

 

 

 

85

80

70

60

55

45

400x200

 

 

 

 

85

80

70

60

55

45

                     

350x300

 

 

 

 

85 *

80 *

70 *

60 *

55 *

45 *

350x250

 

 

 

 

85

80

70

60

55

45

350x200

 

 

 

 

85

80

70

60

55

45

                     

300x200

 

 

 

 

85

80

70

60

55

45

                     

270x180

 

 

 

 

85

80

70

60

55

45

                     

250x150

 

 

 

 

85

80

70

60

55

45

 

56.5 l/m2 or greater per spell

 

Minimum Rafter Pitch

20

22.5

25

27.5

30

35

40

45 to 75

85+

Slate Size                    

600x350

 

150 *

130 *

120 *

110 *

100 *

85 *

80 *

70 *

50 *

600x300

 

 

165 *

120 *

110 *

100 *

85 *

80 *

70 *

65 *

                     

550x300

 

180 *

130 *

120 *

110 *

100 *

85 *

80 *

70 *

50 *

                     

500x300

 

 

130 *

120 *

110 *

100 *

85 *

80 *

70 *

50 *

500x250

 

 

150 *

125 *

110 *

100 *

85 *

80 *

70 *

70 *

                     

455x250

 

 

 

120 *

110 *

100 *

85 *

80 *

70 *

50 *

                     

400x250

 

 

 

 

 

100

85

80

70

50

400x200

 

 

 

 

 

100

85

80

80

80

                     

350x300

 

 

 

 

 

100 *

85 *

80 *

70 *

50 *

350x250

 

 

 

 

 

100

85

80

70

50

350x200

 

 

 

 

 

100

85

80

70

50

                     

300x200

 

 

 

 

 

100

85

80

70

50

                     

270x180

 

 

 

 

 

100

85

80

70

50

                     

250x150

 

 

 

 

 

100

85

80

70

50

 
* Marked items may require longer or improved ring shank nails or increase slate thickness laps etc in areas likely to be exposed to very high winds.  Project specific calculations can be carried out.

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

Sales Office
Penrhyn Quarry
Bethesda
Bangor
Gwynedd
LL57 4YG

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

Download this Roofing Brochure for a Comprehensive Guide to the Technical Requirements and Standards

Download Brochure

Architects and Specifiers

  • Cases Studies
  • Data Sheets
  • CPD
  • NBS Source 
Find out more

Roofing Gallery

Find inspiration in our Roofing Gallery

View Gallery