How Filon Installation Ensures a Leak-Free Roof with Correct Valley Trough

While a roof’s main surfaces are often the focus, its most vulnerable point is the valley – the angle where two slopes meet, designed to channel water and debris away from the roof. A valley failure catastrophically directs water inside, necessitating costly repairs. This makes a leak-free roof dependent on the correct installation of a valley trough. 

This is where a precision-engineered Filon GRP (glass reinforced polyester) valley trough offers a lightweight, durable and robust solution. 

Discover the advantages of Filon GRP valley troughs and how to install them for leak-free roofing.

How GRP Valley Troughs Ensure Leak-free Roofing

To understand why a GRP valley trough is so effective, it’s helpful first to understand the downfalls and problems caused by traditional materials:

Lead valleys

While durable and long-lasting, lead is soft and has high levels of thermal expansion and contraction compared to other roofing materials, so it should only be installed in 1.5m long sections. It requires highly skilled tradespeople to shape and dress it correctly on-site, and as it’s expensive, it can be stolen for its scrap value.

A GRP valley trough eliminates these vulnerabilities through its design and material properties:

• Pre-formed channel: The troughs are 3 metres long factory-produced units. This means there are fewer lap joints along the valley’s length. It is designed as a continuous channel, guaranteeing water is funnelled away efficiently.
• Material integrity: GRP is a composite material made of a UV-stabilised polyester resin reinforced with a glass fibre mat. This creates a product that is incredibly strong, yet flexible and completely impervious to water. It will not rot, corrode or degrade when exposed to water.
• Dimensional stability: Unlike lead, GRP does not expand and contract significantly with temperature changes. It maintains its shape and profile, preventing the stress and fatigue that can lead to failures in other materials.
• Weather resistance: High-quality Filon GRP valleys come with a factory-bonded UV-absorbing layer, which reduces degradation from sunlight and ensures a long service life without becoming brittle.

 

The Advantages of GRP Valley Troughs

Manufactured in our ISO 9001 quality-assured factory, Filon GRP valleys are an excellent choice, ensuring you can achieve a leak-free roofing finish.

Quality material

Filon GRP is manufactured to consistently high standards, ensuring uniform thickness, strength and material quality throughout every trough. This consistency is crucial for performance and longevity and is backed by third-party accreditation from the BBA (British Board of Agrément).

Perfect compatibility

The Filon range of valley troughs is designed to integrate seamlessly with most slate and tile pitched roofing systems, ensuring correct dimensions and profiles.

Ease of installation

The pre-formed nature makes them significantly quicker and easier to install than fabricating a valley on-site. They are also lighter than lead, making them easier to handle on the roof.

Aesthetic finish

Available in a range of colours, Filon valley troughs can be matched perfectly to the main roof covering, creating a neat, professional and aesthetically pleasing finish that blends in.

Durability and longevity

A correctly installed Filon GRP valley trough will last for decades, requiring little to no maintenance and providing peace of mind that this critical part of the roof is secure.

Best practice for leak-proof roof valleys

Beyond the specific steps for valley trough installation, adhering to these universal best practices will guarantee a robust valley.

• Continuous support: The valley trough must be supported along its entire length by a constant, straight and sturdy valley board.
• Correct fixings: Use 25mm long clout-headed nails at maximum 500mm centres to secure the valley trough to the counter battens.
• Keep it clear: After installation, ensure the valley and gutter remain clear of debris. While GRP is smooth and encourages water flow, a build-up of leaves and moss can still cause water to back up.

 

FAQs

GRP Valley Trough Installation tips

While it is a more straightforward process than working with lead, roofing work is potentially dangerous and requires a skilled worker to install correctly and safely. For a guaranteed leak-free roofing system, it is necessary to use a professional roofing contractor experienced in installing GRP valley troughs and to complete the installation in accordance with the relevant parts of BS 5534:2014, BS 8000-0:2014 and BS 8000-6:2023.

What width of valley trough do I need?

The required width depends on the roof pitch and the size of the roof area draining into it. Lower pitches and larger roof areas require wider valleys to handle the larger volume of water. For more specific guidance, contact Filon’s Technical Department.

Are GRP valleys suitable for all roof types?

They are primarily designed for use with tiled or slated roofs, but can be integrated with other systems. They are an ideal solution for most pitched roof constructions that require a reliable, low-maintenance valley.