What are lead valleys and their alternatives

Lead valleys are sheets of lead installed onto boards  to form waterproof linings along the valleys of a pitched roof – where two roof planes come together to form a V-shape. While lead has traditionally been used for this purpose, lead valley alternatives such as GRP and zinc have become increasingly popular in recent years.

Lead valleys vs the alternatives

An important detail in a roof’s weatherproofing, lead valleys and their alternatives direct rainwater off the adjacent roof slopes into the gutters. The design and installation of valleys must be done with care, to ensure they can cope with the expected rainfall, are wide enough to avoid the build-up of debris, and are free of defects which could cause the valleys to leak. 

Lead has long been used as the go-to material for roof valleys and roof details, such as flashings around chimneys, dormers and abutments, as well as gutters. Since lead is a malleable material, it is possible to work it into the right shape. It’s also durable and resistant to corrosion. However, lead valleys also have some significant drawbacks. Lead sheet rolls are heavy to handle which increases the risk of manual handling injuries and lead is a toxic material that poses potential environmental and health concerns if ingested. Specialist skills are needed to install lead valleys to a high standard, and lead valleys are more susceptible to theft, due to the value of scrap metal. Another drawback with lead valleys is that they create an open channel which cut slates and tiles can drop into where storm damage occurs, which risks damage to the lead lining and also can potentially blockages which can inhibit drainage. 

In response to the various challenges associated with lead, alternative products have been developed that are lightweight, easy to install and do not have the toxicity and environmental concerns associated with lead. Common alternatives to lead valleys include zinc valleys and GRP valley systems, such as those offered by Marley.

Roof valleys: lead alternatives from Marley

The Marley complete roofing system includes two alternatives to lead valleys. Made from GRP (also known as glass-reinforced polyester or fibreglass), these dry-fix, mortar-free valley systems offer reliable durability, excellent corrosion resistance and high-quality aesthetics.

• The Universal GRP Dry Valley is compatible with Marley's entire range of clay and concrete roofing tiles and is designed to give the appearance of a closed-cut roof. As the tiles sit snug up to the central upstand, this provides more protection for the cut tiles during storm conditions. Two options are available: a high- and low-profile, and they are available for pitches up to 60°.
• The GRP Slate Dry Valley is designed for use on slate roofs and provides an open valley detail to recreate the look of a traditional lead valley. It features an advanced parabolic gutter section, which improves discharge rates without added gutter depth.

Both the High- and Low-Profile Universal GRP Dry Valley liners and the GRP Slate Dry Valley offer cost-effective and eco-friendly alternatives to lead valleys. They are easy to install, compatible with the full range of Marley products and require minimal maintenance.

For further information about our lead valley alternatives, visit our valley product pages or contact the Marley team.