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Dry Fix GRP Valley Trough Systems

Mortar-less roof drainage dry valley systems. Provides quicker, safer and simpler installation processes compared to traditional wet fix and lead material alternatives.

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Features & Benefits

• Robust and cost effective material with no scrap or resale value
• Maintenance free, light and easy to handle and cut
• Substantially quicker installation time than mortar based process
• Adequate flexibility for roof pitch variation
• Can be installed in virtually all weather conditions
• UV inhibiting film restricts mould and fungal growth
• Fully flexible closers material enables precise fitting to troughs and other roof materials
• Valley troughs supplied in 3m lengths


• Valley troughs provide a weatherproof drainage channel where there are changes in direction or material in the roof structure
• Suitable for:
- concrete or clay roof tiles
- natural and man-made roof slates
• On roof pitches up to 60°
• Head closers units close the up-stand at the top of dry fix valley troughs that finish at a ridge section and form a watertight saddle with a corresponding valley troughs
• Eaves closer units protect the underside of the valley trough from water ingress and forms a water run off to the gutter

Technical Information

Installation advice

• Valley boards must be installed to support the valley trough. This is a requirement of the NHBC Standards
• The underlay material and battens should be fixed in accordance with the standard roofing best practice; with a batten running the length of the valley on each side to accommodate the dry fix valley trough’s water bar section
• The valley troughs are fitted onto the valley boards and should be firmly fixed from the eaves closure section upwards using suitable large headed roofing nails on either side
• All overlap troughs should be at least 150mm when measured in the vertical. Care should be taken to ensure than the central raised section is positioned central to the valley
• If the valley trough finishes at a ridge with a corresponding valley, the head closer units can be used
• The head closer must overlap both valleys troughs by 150mm and form a neat waterproof seal

• Tiles or slates being laid into and over the troughs should be laid in accordance with the manufacturer’s recommendations
• When the slating/tiling has been completed, the eaves closer unit should be cut with a sharp knife or scissors to allow water discharge into the rain water gutter
• It is important to ensure that the valley troughs are cleared of any debris on completion to ensure that water flow is not impeded
• The installation of GRP valley troughs and roof slating/tiling must be carried out in accordance with all relevant British Standard clauses

How to order

  • Measure the valley length up the slope and divide by 3 (product length) to determine the quantity of dry fix GRP valley troughs required
  • Allow a minimum vertical overlap of 150mm lap if it’s necessary to join valley rough sections together

Material and colour choice

• 'Lead' grey colour
• Valley – Glass Reinforced Polyester
• Closers – flexible rubber composite material

Quality, Regulations and Standards

• Complies with the NFRC Technical Bulletin – 28
• Satisfies NHBC requirements
• BBA Approved
• Fire rated to BS 476 part 3 – SAB & BS 476 part 7 Class 3

  • nbs plus
  • riba

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