Roofing battens are nailed into the rafters (or roof joists or trusses) and provide support for the roof tiles or slates.
The updated BS 5334:2014 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. For example, 25x50mm battens are required for single-lap Modern roof tiles laid on rafters with a 600mm span.
The correct batten spacing is necessary because it corresponds to the gauge and head lap of the roof covering being installed. This is important because the correct gauge and head lap has a direct influence on a tiles resistance to withstand the ingress of rainwater through capillary - ensuring that the roof remains watertight. It is also important aesthetically, so that the tiles on the finished roof are equally spaced.
Battens should be fixed to rafters set at centres not more than 600 mm apart and should span at least 3 rafters. To ensure this, the battens should be at least 1.2 m long.
Not more than one in four battens should be joined over one truss for gauges over 200mm. Below 200mm there can be 3 consecutive joins in any twelve battens.
The best way to meet this is to use a spread of lengths so that joints can be staggered.
Battens should be nailed to the centre of the rafter and any joints should be directly over a rafter with the batten square cut, tightly butted and skewed nailed.
When set in mortar a cut batten end should be treated or the batten turned so that the treated end is in the mortar. With dry fix systems the batten cut end is deemed to be within the roof and does not require treating..
- BS 5534,The Code of Practice for Slating and Tiling
- BS 8000-6, Workmanship on Building Sites, Code of Practice for slating and tiling of roofs and claddings
- NFRC Technical Bulletin 33 Graded battens for slating and tiling