When all the slates are sorted the total width of each length is measured
or estimated. This figure is then divided by the width of the roof to determine
how many courses can be laid in each length. For a gable to gable roof
this is simple. For a hipped roof or one with a more complicated plan,
adjustments to the calculation have to be made for each course or few courses.
A note is made of how many courses there will be of each length often by
making pencil marks on the side of the stick.
The slater can now set out the roof
for the calculated number of courses.
The first step is to make a mark
for each slate course on a rod or batten as long as the rafter but making
allowance for the head lap. In some regions several head laps are marked
on the stick - typically 1, 2 and 3 inches with half inches shown as dots
- and the approrpiate haed lap is set against the mark for the next
but one slate below.
This is repeted for each course.
The rod can now be used to mark the lath or batten position for each course
on the rafters.
shows the marks for the under-eaves, first, second and third courses.