Counter battens are timber battens fixed in the direction of the roof slope, with the tile or slate battens then fixed across them. They are used in roof build-ups where a drainage, ventilation or fixing zone is required above the underlay or supporting layer.
Counter battens and tile battens do different jobs
The horizontal tile or slate battens carry the roof covering. Counter battens run up the slope beneath those battens. Treating the two as interchangeable is where a lot of confusion starts.
Counter battens do not automatically need BS 5534 grading
NFRC guidance says counter battens do not need to be graded to BS 5534 provided they are fully supported and fit for their intended use. That does not mean any timber size is suitable for every roof: the roof design still decides the section, treatment, fixing and layout.
25 × 38mm and 25 × 50mm treated battens can be useful options where the design permits
Wern-Wood stocks a 25 × 38mm × 4.8m green treated batten and 25 × 50mm green treated battens in several lengths. Both are general treated timber, not BS 5534 graded tile/slate battens.
The membrane and counter-batten detail must work together
Counter battens are often discussed alongside breathable roofing membrane, but the correct build-up depends on whether the underlay is supported, the roof covering and the required ventilation/drainage path. Follow the membrane and roof-covering specification rather than adding counter battens by default.
Use graded battens where the horizontal battens support tiles or slates
For the roof-covering battens themselves, use the grade and section specified for the roof. Our commercial roofing option is the BS 5534 Roofing Batten – 25 × 50mm × 4.8m.
See the Roof Batten Sizes & Spacing Guide for 25 × 38mm vs 25 × 50mm and batten gauge.
