The two common graded roofing-batten sections are 25 × 38mm and 25 × 50mm, but the correct size and spacing depend on the roof covering, support span, roof pitch and required headlap.
If you already know the specification, shop Roofing Battens. Wern-Wood's tile/slate roofing-batten product is the BS 5534 graded 25 × 50mm × 4.8m batten.
25 × 38mm and 25 × 50mm are both recognised graded batten sizes
BS 5534 guidance distinguishes between 25 × 38mm and 25 × 50mm battens according to the roof covering and support spacing. The larger section is not simply a premium version of the smaller one: the roof specification decides which minimum section is acceptable.
As a practical summary, 25 × 38mm graded battens appear in specifications for several tile and slate systems, while 25 × 50mm is required in others, particularly as support spans increase. Always check the installation guidance for the exact tile or slate being fitted.
Our green 25 × 38mm batten is not a BS 5534 roofing batten
Wern-Wood now stocks a 25 × 38mm × 4.8m green treated timber batten, but it is general treated timber rather than a graded tile/slate batten. A piece of timber does not become BS 5534 roofing batten simply because its dimensions are 25 × 38mm.
For general treated battening we also stock 25 × 50mm treated timber battens in several lengths.
How far apart should roof battens be?
Roof-batten spacing is normally called the batten gauge. There is no universal 300mm, 325mm or 350mm answer. The permitted gauge comes from the exact tile or slate, roof pitch and required headlap.
For variable-gauge tiles, calculate the maximum gauge from the required headlap
The basic relationship is:
Maximum batten gauge = tile length − minimum required headlap
For example, a 420mm tile requiring a minimum 75mm headlap has a maximum gauge of 345mm. That does not mean every course should automatically be fixed at 345mm. Measure between the required eaves and ridge positions and divide the roof into a whole number of courses so the actual gauge stays at or below the permitted maximum.
Do not stretch the gauge to make the courses fit
If the roof does not divide neatly, reduce the gauge slightly and distribute the courses evenly. Increasing the gauge reduces the headlap, so exceeding the manufacturer's maximum can change the weather performance of the roof covering.
Counter battens are different from tile or slate battens
Counter battens run in a different direction and are used as part of particular roof build-ups. Where they are fully supported and fit for the intended design, NFRC guidance does not require them to be graded to BS 5534. See What Are Counter Battens on a Roof?.
Use the fixing specified for the roof
Current NFRC guidance refers to 3.35mm diameter nails, typically 65mm long, while noting that the fixing calculation can require a different size or type. Read What Nails Should You Use for Roof Battens?.
For the grading and marking itself, read Do Roof Battens Need to Be BS 5534 Graded?.
