Roof Battens and Counter-Battens

Roof battens (also called roofing lath, tiling battens or slate battens) are narrow strips, usually sawn softwood but sometimes metal, fixed horizontally across rafters, trusses or a deck. They provide the fixing points for tiles, slates, shingles or metal sheets. Their spacing, known in the UK as the gauge, is set by the length and headlap of the roof covering.

Counter-battens are battens laid vertically, running up the slope along the line of the rafters on top of the underlay or deck. The horizontal tiling battens are then fixed on top of them, producing a grid.

Why counter-battens are used

• They lift the tiling battens off the underlay so that any water reaching the underlay can drain freely down to the eaves instead of collecting behind battens.
• They create a continuous ventilated space between underlay and covering, which UK guidance requires in some combinations of low-resistance underlay and air-tight coverings.
• They allow tiles to be fixed over a continuous deck or rigid insulation in warm roofs.

Regional practice

Battens are standard under tile and slate roofs in the UK, Ireland, Europe, Australia and New Zealand. In the UK, BS 5534 is the code of practice for slating and tiling and covers batten specification and fixing. North American roofs more often use a solid deck, although battens (sometimes called strapping or furring) are used for some tile, slate, stone-coated steel and metal roofs, and counter-batten systems are used to create ventilated "cold" roofs. In batten-seam metal roofing, battens form the raised seams between pans.

Durability

Timber battens are usually treated against decay. Because battens carry the whole covering and resist wind uplift through their fixings, undersized or poorly fixed battens are a common cause of roof failure in storms. Batten size and fixing requirements depend on rafter spacing, covering weight and exposure, and are set by the relevant standard.