Load distribution: They prevent the fastening screws or bolts from sinking into or causing tears in the roofing material by spreading the pressure over a larger area.
Protection: They protect the roofing material from damage caused by the fastening elements.
Waterproofing: Depending on their design, pressure plates can also help maintain the roof's waterproofing, especially if they have integrated seals.
The choice of the right pressure plates depends on several factors, including the type of roofing, its thickness, the expected loads, and the specific requirements of the project. Pressure plates are manufactured with different profiles, which provide their strength and rigidity. The profile used depends on the application. The most common profiles are flat, shallow dish, or deep dish - the names refer to the shape on the underside of the pressure plate.
Flat pressure plates should be used when the roofing is attached directly over a rigid surface such as plywood.
Shallow dish pressure plates should only be used when securing compressible insulation. The pressure plate sinks slightly into the insulation so that the head of the fastener is below the surface of the plate. This prevents the fastener head from contacting the roofing material, which could damage the waterproofing over time.
Deep dish pressure plates should be used to secure compressible insulation with a 'hex-head' fastener. The deeper profile ensures there is enough space so that the head of the fastener does not contact the membrane.
It is important to ensure that the pressure plate used has a sufficiently large hole diameter to accommodate the fastener
A round or oval pressure plate is typically used in situations where the shape of the pressure plate contributes to specific functional requirements or installation guidelines. Here are some common reasons for using a round or oval pressure plate:
Aesthetic considerations: In some cases, the shape of the pressure plate may be aesthetically important, especially if it remains visible after installation. Round or oval pressure plates may better complement the design or architecture of the building.
Specific attachment points: If the attachment points on the roof have a specific shape (such as round penetrations or cutouts), a round or oval pressure plate may fit better and provide better sealing around these points.
Load distribution: Sometimes, a round shape may be better for evenly distributing the load around a fastening point. This can be particularly important for fastenings sensitive to stress or deformation.
Specific roofing materials: Depending on the type of roofing and the installation method, round or oval pressure plates may be used to better match the characteristics of the roofing material. For example, if the roofing material is flexible, a round pressure plate can help distribute the load evenly.