Roof Batten Calculator
Calculate total linear footage of roofing battens and determine precise batten gauge for tile overlaps. Includes database of 20+ common tile profiles.
About
Correct batten spacing, or "gauge," is the single most critical factor in preventing roof leaks. If the gauge is too wide, the tiles will not overlap sufficiently (the "headlap"), allowing wind-driven rain to penetrate the sub-roof. If the gauge is too narrow, you waste materials and risk running out of tiles. This tool calculates the precise gauge required based on the rafter length and the specific tile profile, ensuring the overlap meets manufacturer specifications.
For professional roofers and serious DIYers, the calculation handles the variable geometry of the roof slope. It determines the number of courses required and subsequently the exact spacing to ensure the top course finishes correctly at the ridge without an awkward cut. The logic accounts for the fixed position of the eaves batten and the ridge batten, distributing the remaining space equally.
Formulas
The calculation for the batten gauge G involves dividing the usable rafter length by the number of courses. The number of courses N is derived from the maximum permissible gauge for the chosen tile.
First, determine usable length Luse:
Luse = Lrafter − deaves − dridge
Calculate number of rows N (rounded up):
N = ceilLuseGmax
Calculate final gauge Gfinal:
Gfinal = LuseN
Total linear footage is the product of rows and roof width, plus a waste factor w (typically 1.10).
Reference Data
| Tile Profile | Min Gauge | Max Gauge | Min Headlap |
|---|---|---|---|
| Standard Concrete Interlocking | 280 mm | 345 mm | 75 mm |
| Clay Plain Tile | 85 mm | 100 mm | 65 mm |
| Natural Slate (20x10) | 200 mm | 250 mm | 100 mm |
| Pantile | 300 mm | 340 mm | 75 mm |
| Double Roman | 315 mm | 343 mm | 75 mm |
| Flat Profile (Modern) | 290 mm | 345 mm | 75 mm |
| Spanish Clay | 320 mm | 370 mm | 80 mm |
| Large Format Slate | 280 mm | 380 mm | 90 mm |