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An Introduction to Dry Fix Roofing

Written On by RTA Member

Dry fix roofing has been around in the UK for almost 50 years, but its usage is increasing thanks to improvements in standards.  The publication of BS 8612 in early 2018, is welcomed by the Roof Tile Association, particularly with the requirements introduced in the 2014 revision of BS 5534, ensuring all fixed ridge, hip and verge systems meet agreed standards.  All association members focus on technical performance and durability when manufacturing their roofing products. They are designed to mechanically fix roof components to make sure they withstand the highest wind loads a roof is ever likely to encounter, while also providing the required high-level ventilation.  Among the many advantages of dry fix products, the maintenance-free aspects come top of the list for many contractors and clients.

BS 8612 provides material specifications and durability criteria, as well as performance criteria for rain resistance and mechanical resistance against wind loads. The Standard also outlines the following performance criteria:

A dry ridge system must:
1. Withstand wind loads to prevent the system and associated ridge and hip tiles from dislodging
2. Prevent the ingress of driving rain and snow
3. Where applicable, provide the high-level roof space ventilation in accordance with BS 5250
4. Remain durable
BS 8612 provides test procedures to determine the resistance of a dry ridge/hip system to vertical and horizontal wind loads. It also provides the methodology to predict wind load for any given situation.
For ridge and hip rolls that dress and bond to the shape of tiles, there are test methods to determine the strength of the material after aging, the bond strength of the adhesive and the extent of elongation. There are two classes to define whether a ridge/hip roll is suitable for a) flat and low-profile tiles, or b) for high profile tiles such as deep-dish bold roll tiles and pantiles.

A dry verge system must:
1. Resist predicted wind loads
2. Close the gap between the tiles/slates and wall or bargeboard top
3. Drain any water from the roof away from the gable wall
4. Act as one of the fixings for the roof tiles or slates

BS 8612 sets out test methods to determine the resistance of a dry verge system to horizontal and vertical wind loads. It also provides information, based on BS 5534, to determine the predicted wind loads on verges. The vertical uplift resistance data can be used to check the dry verge system is suitable to resistance wind loads on the roof tiles at verges when used in conjunction with their primary fixings.

The verge system must prevent water from running down the gable wall in concentrated streams, which can lead to staining and mould growth on the wall. In this regard, BS 8612 gives a test method to determine if water running through a verge system will run away from the wall. The same test can be carried out on continuous dry verge systems and in particular the joints in continuous systems.

So, what does this all mean for the designer, client and roofing contractor? You can be sure that products that that are in full compliance with BS 8612 will offer reliable technical performance and long-term durability.

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