Roof Batten Calculator UK
Calculate horizontal tile-batten rows and linear metres from the actual setting-out distance, the length each row must span and the tile manufacturer’s maximum permitted batten gauge. No fixed 300 mm spacing, two-slope assumption or hidden waste percentage.
Calculate tile-batten rows and length
Measure the distance between the first and last tile-batten datum points on one roof slope. Then enter the length each horizontal row must span and the maximum gauge allowed by the exact tile/slate specification.
How the roof batten calculation works
Rows = intervals + 1. The actual even gauge is the datum distance divided by those intervals, so it never exceeds the maximum gauge entered.
Rows × batten-row length × identical slopes gives the base horizontal tile-batten length. Any chosen extra percentage is applied only after that base quantity is known.
Why the gauge is a maximum, not a universal spacing
Roof-tile systems use very different gauges. Current UK manufacturer data illustrates the range: Marley Modern uses up to 345 mm at 75 mm headlap and around 320 mm at 100 mm headlap; Marley plain tiles can use a 100 mm roof gauge; BMI Redland 49 lists maximum gauges such as 282 mm or 307 mm depending on the product/pitch conditions. These figures are examples from those systems, not calculator defaults.
Marley’s setting-out guidance also explains that the maximum gauge may need to be reduced slightly so the distance between the eaves and ridge datum points divides into even courses while maintaining minimum headlap. That is why this calculator rounds the number of intervals up and reports the resulting even gauge.
Current UK manufacturer references checked for this calculator:
Marley — setting out tiling battens
Worked example
Suppose the measured first-to-last batten datum distance is 3.40 m, each row spans 8.00 m, and the chosen tile specification permits a maximum 345 mm gauge. 3,400 ÷ 345 = 9.86, so the calculator uses 10 intervals and therefore 11 batten rows. The adjusted even gauge is 340 mm. One slope needs 88.00 linear metres; two genuinely identical slopes need 176.00 linear metres at the default 0% extra.
Use the roof/tile setting-out method to establish the first and last batten positions. Do not assume the whole slope length equals the gauged distance.
Read it from the exact tile/slate technical data for the intended pitch, headlap and conditions.
If roof planes differ in gauged length or batten run, calculate them separately and add the results.
What this calculator deliberately leaves out
- Selection of roof tile/slate, roof pitch, headlap or exposure specification.
- Batten cross-section/timber grade and structural/fixing requirements.
- Counter-battens, tilting fillets, eaves/ridge special details and short local battens.
- Stock lengths, joint staggering, supplier pack quantities and cutting layout.
- An automatic waste or cutting percentage.
Planning estimate only. Batten spacing and size affect weather resistance and site safety. Check the current tile/slate manufacturer fixing and setting-out instructions, project specification and applicable standards before installation or ordering.
Continue the roofing estimate
Frequently asked questions
Where do I get the batten gauge?
Use the current technical/fixing information for the exact roof tile or slate and the specified roof pitch, headlap and exposure conditions. Enter the manufacturer’s maximum permitted gauge, not a generic spacing.
Why does the calculated gauge sometimes come out smaller?
The maximum gauge is a limit. The measured distance between the first and last batten datum points may not divide exactly by that value, so an extra interval is required and the rows are then spread evenly at a slightly smaller gauge.
Can I enter two roof slopes?
Yes, but only when both slopes genuinely share the same datum distance and batten-row length. Otherwise calculate each roof plane separately.
Does this tell me how many timber lengths to buy?
No. It estimates horizontal tile-batten linear metres. Stock length, joints, staggering, cuts and supplier quantities must be planned from the actual timber and roof layout.