Roof batten spacing, also known as the ‘gauge’, is the vertical distance between each horizontal batten on a roof. It determines how the tiles or slates overlap and is critical for ensuring the roof is weathertight, structurally sound, and compliant with building regulations.

Batten spacing is calculated by subtracting the head lap from the total length of the tile or slate. The formula is: Batten Spacing = Tile Length − Head Lap. For example, a 300mm tile with a 75mm head lap requires a batten spacing of 225mm.

The standard head lap depends on the roof pitch, as defined by BS 5534 in the UK. For pitches above 30°, the minimum head lap is 75mm. For pitches between 22.5° and 30°, it is 100mm. For pitches below 22.5°, a minimum of 125mm is required to prevent wind-driven rain penetration.

Yes. While the physical batten spacing (gauge) is simply the tile length minus the lap, the roof pitch dictates the minimum required head lap to ensure weathertightness. A lower pitch requires a larger lap, which in turn reduces the batten spacing (gauge) and increases the number of courses needed.

BS 5534 is the British Standard for slating and tiling. It specifies the minimum head laps based on roof pitch, maximum rafter spacing (typically 450mm or 600mm), and the required batten sizes (e.g., 25x38mm for 450mm rafter centres). Compliance ensures the roof can withstand wind uplift and severe weather.

To find the number of batten courses, divide the total length of the rafter by the batten spacing. For example, if your rafter is 4.5 metres long and your batten spacing is 0.225 metres, you will need 20 courses of battens (4.5 ÷ 0.225 = 20). Always round up to the nearest whole number.

According to BS 5534, the size of the batten depends on the rafter centre spacing. For rafter centres up to 450mm, a minimum batten size of 25 x 38 mm is required. For rafter centres up to 600mm, the minimum size increases to 25 x 50 mm. Battens must also be treated against insect attack and fungus.

No. Natural slates are typically hung by a nail and have a variable gauge, often calculated as half the slate length minus the lap (since they are hung in double courses). Concrete or clay tiles are hung in single courses, so their gauge is the full tile length minus the lap. Always follow the manufacturer’s specifications for the specific product.