Tile Battens

Battens (in North America sometimes called lath, strapping or purlins on tile roofs) are lengths of sawn timber fixed horizontally across the rafters or roof deck. Tiles hang from them by their nibs and are nailed or clipped to them, and slates are nailed or hooked to them. The distance between battens, the gauge, equals the exposure of each course.

Counter-battens

On many modern roofs a second set of timbers, counter-battens, runs up the slope beneath the battens. They lift the battens off the underlay so that water that gets past the tiles can run down to the gutter and air can circulate. Canadian guidance for one tile system uses 38 x 9.5 mm (1 1/2 x 3/8 in) counter-battens and sets additional straps beside valleys, hips and walls.

Sizes and spacing

Batten size depends on rafter spacing, tile weight and national rules. Canadian guidance for one concrete tile system calls for 25 x 100 mm (1 x 4 in) spruce battens of No. 2 grade or better, nailed into the trusses with nails long enough to penetrate at least 25 mm (1 in). The first batten is set from the eave blocking and the rest are spaced equally between eave and ridge, no more than 345 mm (13 3/4 in) apart.

Setting out

1. Mark the eave and top batten positions from the tile manufacturer's gauge and the first-course details.
2. Divide the distance into equal gauges within the manufacturer's maximum.
3. Snap chalk lines on the rafters or counter-battens.
4. Fix battens to each rafter, joining them only over supports.

UK practice

In the UK, BS 5534 covers the specification of battens alongside tile fixing, and BS 8000-6 covers workmanship on site. Battens there are commonly graded and marked as suitable for roofing. Timber treatment and grading rules differ by country and should be taken from national standards and the tile manufacturer.