What is a dry ridge system and why should I use one?

A dry ridge system mechanically fixes ridge tiles to the ridge board without mortar. It uses unions, clamps and screws instead of sand-cement bedding. Dry ridge systems are now required under BS 5534:2014 for new builds and re-roofs in the UK. They last longer than mortar, are wind-resistant, and allow ventilation at the ridge.

How many ridge tiles do I need per metre?

Standard dry ridge tiles have a cover length of approximately 330mm, so you need roughly 3 ridge tiles per metre of ridge. Always round up and add 10% wastage for cuts at the ends.

Do I need ventilation strips with a dry ridge system?

Most dry ridge systems include or require ventilation strips to provide the equivalent of a 5mm continuous gap at the ridge. This meets the ventilation requirements of BS 5250 and Approved Document F. Some systems have ventilation built into the roll.

Can I use a dry ridge system on clay tiles?

Yes. Most dry ridge systems work with both concrete interlocking and clay tiles. However, you need to ensure the ridge tile profile (angular or half-round) is compatible with your main roof tile. Check manufacturer compatibility before ordering.

How long does ridge roll last?

Quality ridge roll made from UV-stable polypropylene or similar material typically lasts 20-30 years. It acts as a weather barrier beneath the ridge tiles and should run the full length of the ridge with 150mm overlaps at joins.

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Dry Ridge Calculator — Dry Ridge System Components

Calculate all components needed for a dry ridge system including ridge tiles, unions, connectors, end caps, ridge roll and fixing screws. Based on UK manufacturers' specifications.

Ridge Length

Total length of the ridge (eave to eave measurement along the top)

Tile Type

Main roof tile type

Ridge Tile Profile

Angular for modern roofs, half-round for traditional

Include ventilation strips

Required for BS 5250 ridge ventilation compliance

How We Calculate This

This calculator works out all the components you need for a dry ridge system based on your ridge length and tile type. It uses standard UK cover lengths and manufacturer guidelines to calculate quantities.

Key formulas

Ridge tiles: Ridge length (mm) ÷ 330mm cover × (1 + wastage %)
Unions/connectors: Number of ridge tiles − 1 (one between each tile)
End caps: 2 per ridge run (one at each end)
Ridge roll: Full ridge length + 150mm overlap per join
Fixing screws: 2 per union + 2 per end cap + 1 per tile clamp
Ventilation strips: One per ridge tile bay

Standards

Dry ridge systems are required under BS 5534:2014 for all new roofs and re-roofs. The system must resist wind uplift forces and provide adequate ventilation as per BS 5250.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.