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Dry Verge Calculator — Units, Starter Kits & End Caps
Calculate dry verge units needed for gable ends. Includes starter kits, left/right end caps and fixings, based on your tile batten gauge (course spacing).
Slope length from eaves to ridge on one gable
Typically 2 for a standard house
Usually 1 eaves starter per gable
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How We Calculate This
Each dry verge unit covers one tile course at the gable edge, so the number of units is governed by your tile’s batten gauge (the course spacing up the slope) — not the tile width. Gauge is the tile length minus the headlap, so a 5m gable holds far more courses than dividing by the tile width would suggest.
The formula
Verge units per gable = Gable rafter length (mm) ÷ Batten gauge (mm), rounded up
Total units = Units per gable × Number of gables
Batten gauge = tile length − minimum headlap (BS 5534 / BS 8612). Example: Marley Modern 420mm − 75mm headlap = 345mm maximum gauge.
Typical batten gauges (course spacing)
- Concrete interlocking: ~345mm max (e.g. Marley Modern); reduce for steeper pitches
- Smaller interlocking: ~257–307mm (e.g. Redland 49, pitch-dependent)
- Large-format concrete: ~355mm max (e.g. Redland Stonewold II MK2; BMI Product Data Sheet)
- Plain tiles (double-lap): ~100mm max — many more courses, so many more units
Always confirm the gauge from your tile’s datasheet and follow the manufacturer’s dry-verge fixing instructions for fixings, starters and end caps.
Frequently Asked Questions
One dry verge unit covers each tile course, so divide your gable rafter length (in mm) by your tile batten gauge — the course spacing, NOT the tile width. Batten gauge = tile length − headlap (e.g. Marley Modern 420mm − 75mm = 345mm max gauge per BS 5534/BS 8612). For a 5m gable at 345mm gauge that is ceil(5000 ÷ 345) = 15 units per side; multiply by the number of gables.
Starter kits include a special bottom verge unit that connects to the fascia board and provides the starting point for the dry verge system. You need one starter kit per gable end.
Yes. Dry verge end caps are handed — you need a left-hand and a right-hand cap at the top of each gable. These close off the verge at the ridge junction.
BS 5534:2014 requires perimeter (verge) tiles to be mechanically fixed (twice) on new builds and re-roofs in the UK — mortar alone is no longer acceptable as the sole fixing. BS 8612:2018 is the specific standard for dry-fix ridge, hip and verge systems. A BS 8612-compliant dry verge system satisfies these requirements and replaces traditional mortar verge pointing.
Yes. Remove the old mortar verge, clean back the tile edges, and fit the new dry verge units with the appropriate starter kit. Most systems are designed for retrofit as well as new build.
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Last updated: June 2026
Verified against UK standards · estimates only, confirm with your supplier.