Universal GRP Dry Valley

A roof valley is formed where two roof slopes come together. It can be one of the most vulnerable parts of a roof’s weatherproofing, as it is prone to debris build-ups and poor drainage, which can lead to water infiltration.

  • Dry fix, mortar free system
  • Durable GRP technology
  • Simple and fast installation
  • Can accommodate up to a 20° pitch variance either side of the valley
  • Performs on pitches up to 60°
  • Gives a finished appearance of a close cut roof


GRP dry valley troughs help to mitigate these problems, providing a clear and continuous path for efficient rainwater discharge.

Marley’s GRP dry valley troughs are compatible with our entire range of clay and concrete roofing tiles and give the appearance of a closed-cut roof. They provide a lightweight and reliable alternative to traditional zinc valleys and are suitable for dry-fix installation. GRP dry valley troughs are also easy to install, as they are simply nailed in place.

Two GRP valley trough options are available: high profile and low profile. Both are provided in lengths of 3,000mm and are easy to cut to size.

Provides weathertight ventilation in the roof slope

Provides up to 10,000mm² free area of ventilation

For natural, mechanical or soil pipe ventilation

For use with all concrete plain and interlocking tiles

Technical Data

Accommodates up to a 20° pitch variation either side of the valley

Continuous support for the valley through must be provided using ply boards

Rafter pitch

Max. valley length

Min. lap length

15 to 17°



17.5 to 22.5°



22.5 to 29°



30 to 34°



35 to 39°



40 to 44°



45 to 49°



50 to 55°




This table is a guide to the recommended application criteria. It assumes a standard roof intersection of 90° and a roof drainage area of 100m². For applications other than this, specific advice should be sought from our technical department.

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