To calculate the batten gauge = (Length minus Lap) divided by 2 Take the length of the slate, deduct the head lap and divide the answer in half for the gauge dimension.
For a 500mm long slate with a 100mm head lap the gauge is 500-100 = 400 x 0.5= 200mm. The gauge is 200mm
To Calculate the nail hole position = Gauge + Lap + 4
In the above case the nail holes should be 200+100+4=304mm from the leading edge of the slate.
Last Updated: November 19, 2010