This table allows you to confirm the correct Batten Gauge (distance between battens) for your chosen slate length and lap. It also allows you to determine the holing gauge (distance from hole to tail of slate) and the number of linear metres of batten per m2 of roof.
The batten gauge can also be calculated using the formula
Batten gauge = (length of slate-headlap)/2.
The holing gauge can be calculated as
Holing gauge = batten gauge + headlap + 10mm.
The most commonly used slate size in Southern England is 500x250mm and 400x250mm in Scotland and the North of England.
Most stock slates will be pre-holed at 75, 90 or 100mm, allowing you the versatility of different pitches – commonly 25 degrees in moderate exposure zones and 30 degrees in severe exposure zones.
Next Step: Now we have determined the type of slate, exposure, headlap and coverage, fixing method and batten gauge, what remains is to decide on your preferred choice of details for Ridges, Valleys, Eaves and Verges.