Lay the underlay starting at and parallel to the eaves maintaining a consistent tautness.
How to felt and batten a slate roof.
Joints should be directly over rafters with the batten square cut tightly butted and skewed nails.
The most commonly used slate size in southern england is 500x250mm and 400x250mm in scotland and the north of england.
Holing gauge batten gauge headlap 10mm.
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 m 2 of roof.
The holing gauge can be calculated as.
What roof pitch do i need for what slate size generally speaking 20 degrees is the lowest advisable pitch for a slate roof depending on the size of the slates and how much that the roof is exposed to.
Roofing felt was introduced primarily to act as a secondary barrier against wind driven snow and rain but its use also causes a reduction in air movement within the roof space particularly if the roofing felt is impervious and this effect is often compounded by the introduction of insulation.
Roof battens and gauge the gauge is the space between the roof battens this will set the overlap of your chosen slate in most cases.
Start at the lower edge of the roof nailing the batten into place at the centre of the rafter.
The batten gauge can also be calculated using the formula.
Start at the lower edge of the roof and position the first batten so that the slates tiles give the required overhang over the fascia set the distance at both ends of the roof and run a string line between check along the line to make sure that the distance is fairly consistent and satisfactory fascia boards may sometimes wonder a little bit but this can be checked by eye looking along the front face.
Batten gauge length of slate headlap 2.