How many dry verge units do I need?

Divide your gable rafter length (in mm) by the tile width. For standard 330mm interlocking tiles on a 5m gable, you need approximately 16 units per side. Multiply by the number of gables.

What are dry verge starter kits?

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.

Do I need left and right end caps?

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.

Is dry verge required by building regulations?

BS 5534:2014 requires mechanical fixing of verge tiles on new builds and re-roofs in the UK. Dry verge systems comply with this standard and replace traditional mortar verge pointing.

Can dry verge be retrofitted to existing roofs?

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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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 by tile width.

Gable Rafter Length

Slope length from eaves to ridge on one gable

Number of Gables

Typically 2 for a standard house

Tile Width

Width of your main roof tiles

Price Per Unit (optional)

How We Calculate This

This calculator determines the number of dry verge units from your gable rafter length and tile width. Each verge unit clips to one tile course on the gable edge.

The formula

Verge units per gable = Gable length (mm) ÷ Tile width (mm)

Total units = Units per gable × Number of gables

Standard UK tile widths

Small format: ~300mm
Standard interlocking: ~330mm (Marley Modern, Redland 49)
Large format: ~380–420mm (Redland Regent, Marley Wessex)

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.