The updated bs 5334 code of practice for slating and tiling specifies a number of batten sizes based upon the span of the rafters and the product being used.
Roof batten spacing for plain tiles.
Underlay 267 x 165mm plain tile.
The gauge is in fact the same as the margin which is the length of the tile exposed.
According to bs 5534 the appropriate batten size will depend on the span of the rafters and the roof covering.
This is where you will place your final batten to allow the tile lugs to fit without pinching or breakage.
Typical details plain tile.
Double lap tiles such as plain tiles 65mm is ok.
Just short of the centre of the gutter.
This will allow the tile lugs to fit nicely into this gap without danger of pinching or breaking them.
Measure the height of the roof from the top of your second batten to about 30 millimetres short of the top of the roof.
Size overall 268 x 165mm minimum pitch 35 maximum pitch subject to fixing specification 90 minimum headlap below 90 65mm at 90 35mm maximum headlap 88mm minimum gauge batten spacing 88mm maximum gauge batten spacing below 90 100mm at 90 115mm hanging length approx 248mm cover all figures are net and do not allow for.
Setting out up the roof gauge set the first batten at eaves to allow the tails of the eaves course tiles to overhang the fascia by 40 to 45mm ie.
Batten spacing measure the distance between the top of the second batten and 30mm short of the top of the roof.
Again 75 mm depending on pitch.
Technical data roof vertical minimum roof pitch 35 75 headlap minimum 65 mm 38 mm batten spacing at max.
Mortar bedding 267x247mm tile and half.
Set the last batten at the ridge so that the ridge tiles will overlap the top course of tiles by at least 75mm.
38 x 25mm s w.
Slate gauge should be all the same and no real need to adjust gauge to suit rafter length.
Batten for rafters at max.
For example 25x50mm battens should be used for single lap modern roof tiles when laid on rafters with a 600mm span.
Not strictly true headlap is dependant on roof pitch on interlocking tiles can be 75mm 3 inche lower pitch increase lap and adjusting only last few courses is shoddy practice.
Gauge 100 mm 114 mm size of tile 265 x 165 mm 265 x 165 mm covering capacity at 60 tiles per m253 tiles per m2.