Dry Ridge Calculator — Dry Ridge System Components

A dry ridge system mechanically fixes ridge tiles to a timber ridge batten (secured to the rafters with stainless batten straps) without mortar. It uses unions, clamps and screws together with a ventilated ridge roll. BS 5534:2014 requires all ridge and hip tiles to be mechanically fixed — by a dry-fix system, or by mortar bedding combined with mechanical clips/screws; mortar alone is no longer permitted. Dry-fix systems are durable, wind-resistant and provide ventilation at the ridge.

Standard UK ridge tiles are 450mm long, and in a dry-fix system they butt against a union with no overlap, so the cover is about 450mm — roughly 2.2 ridge tiles per metre of ridge. Always round up and add about 10% wastage for cuts and breakages. Short heritage ridge tiles are 300mm, giving about 3.3 per metre. For a detailed ridge tile quantity estimate, use our Ridge Tile Calculator.

Ridge ventilation in a dry-fix system is provided by the ridge roll itself, not by separate per-tile strips. A vented roll delivers around 5,000 mm²/m of airflow — the equivalent of a continuous 5mm gap — which meets the ridge ventilation requirements of BS 5250 and Approved Document F where high-level ventilation is needed. If your roof is ventilated elsewhere (for example at the eaves), a plain unvented roll may be used instead; check your roof's overall ventilation strategy and the manufacturer's instructions (dry-fix systems are covered by BS 8612).

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.

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.