A guide to dry verge systems

The edge of a pitched roof where the tiles finish over the gable end is known as the verge and is traditionally sealed with a layer of wet mortar which over time can deteriorate and even fall out completely, even in a relatively short space of time, requiring replacement. A more durable and maintenance free solution is a dry verge system which uses interlocking caps clipped over the edge of the roof tiles, providing a secure fixing and protecting the roof space from weathering and pest damage.

What does ‘dry verge’ mean?

The ‘verge’ refers to the area on a pitched roof where the edge of the tiles finishes at the gable end. This edge must be finished to protect the roof space from the elements and pests. Traditionally a layer of mortar is used to seal the gap between the roof tiles and the brickwork at the verge and while this forms an effective barrier against the effects of wind and rain as well as attack by pests, settlement and shrinkage can cause the mortar to crack and fall out requiring attention and in some cases replacement of the entire layer.

A ‘dry verge’ replaces traditional mortar with a purpose-built system using tough, weather resistant units which provide a similar stepped look to mortar with a longer lasting and more durable finish. The term ‘dry verge’ refers to the fixing method used which consists of compatible clips and units without the need for ‘wet mortar’. Rainwater may penetrate the verge but is effectively channelled away from the building walls by the verge units which will prevent staining and damp issues on the sides of the property.

What are the benefits of a dry verge system?

A dry verge system offers a number of benefits compared to traditional mortar.

• Installation: A dry verge system is quick and easy to install and can be fitted in all weathers compared to mortar which should not be used in temperatures below 4oC or if heavy rain is forecast.
• Improved aesthetics: A dry verge system gives a roof a neater, more modern finish improving a property’s visual appearance.
• Increased durability: Compared to traditional mortar, a dry verge system offers increased durability and will not crack or fall out over time.
• Less maintenance: Dry verge systems use plastic panels which are durable and able to withstand harsh weather conditions as well as any settlement to the property, meaning no maintenance is required.

Are dry verge systems covered by British standards?

The increase in the use of dry verge systems has led to the introduction of British standard – BS 8612 ‘Dry-fixed Ridge, Hip and Verge Systems for Slating and Tiling’. This is a comprehensive standard, now incorporated in BS 5534, covering the design and installation of dry fix systems.

This standard defines the performance requirements and methods used for the testing of dry fixed systems. Recent times have seen a huge increase in the use of dry fix products with several different systems commercially available. BS 8612 is an industry recognised standard which defines minimum performance and installation criteria for dry fix systems. A system designed and installed in line with this standard offers peace of mind to specifiers and contractors as well as homeowners alike.

How is a dry verge system fixed to the roof?

A dry verge system comprises interlocking units that are fixed to brackets secured to the roofing battens using end clips which are simply hammered into place. This mechanical fixing provides a secure attachment for the dry verge panels and complies with the requirements of BS 8612. The bottom unit has an additional fixing at the eaves which incorporates a plastic ‘comb’ to prevent bird ingress at the roof eaves level.

How does a dry verge system work?

The dry verge system works by providing a physical barrier to wind and rain in addition to preventing bird and pest ingress. The top edge of the verge units fixes over the edge of the roof tiles, creating a mechanical fixing to secure them to the roof and preventing damage by wind uplift, this is not something that is achieved when using mortar.

A requirement of BS 8612 is that the verge units discharge rainwater off the verge and away from the gable wall, preventing staining of the brickwork. The units of a good quality verge system incorporate a small raised edge creating a drip feature stopping rainwater tracking round the verge and staining the gable end. They also incorporate a drainage channel within the unit that can channel away any ingress water within the verge, keeping the roof dry.

Can a dry verge system be fitted to an existing roof?

While installing a dry verge on a new roof may be easier, the system can also be fitted to an existing roof and is an excellent way to improve a building’s durability and finish. The dry verge caps are fixed to the roof battens and any mortar covering the ends of the battens is simply removed to allow the system to be secured. If the battens do not extend far enough over the roof verge or are in poor condition, they should be cut back to the nearest rafter and replaced with a longer piece to accommodate the dry verge panels.

Installing a dry verge system

Installing a dry verge system is a straightforward process requiring no mortar or specialist tools. The verge panels are mechanically fixed so the weather has less impact on the installation compared to wet mortar which cannot be used in very low temperatures or if heavy rain is forecast.

All components of the dry verge are extremely durable and highly resistant to the elements, so the building requires less maintenance and maintains its aesthetic for the life of the building. They are manufactured predominantly with recycled plastic that can also be recycled at the end of its life, making them a sustainable choice. Our installation video provides an easy-to-follow guide to the process of fitting a dry verge system.

Marley‘s roofing range includes a number of products that make up a dry verge system, to view the range, click here or to discuss using our products on your next project, please contact us here.