What is XPS insulation board and how is it made?

Extruded polystyrene (XPS) is a closed-cell, rigid foam insulation board made by melting polystyrene beads and extruding them into dense panels. It typically offers an initial R‑value of around R‑5 per inch, making it effective for interior and exterior wall insulation.

What are the primary benefits of using XPS for external wall insulation?

XPS boards are lightweight yet mechanically strong, have very low moisture absorption and are chemically resistant. They provide excellent thermal performance (R-value about 4.6–5.0 per inch) and resist moisture even when immersed, protecting against mould and rot.

Is XPS insulation suitable for below DPC (damp-proof course) applications?

Yes, XPS insulation is ideal for below DPC use. Thanks to its closed-cell structure, it has excellent water resistance and compressive strength, making it perfect for insulating foundation walls, plinths and areas exposed to ground moisture. It's often used at the base of EWI systems to provide thermal protection where other insulation types may absorb water.

Can XPS insulation be used on solid and cavity walls?

XPS is ideal for insulating solid walls externally, timber, masonry, or system-built housing, and can even be applied below damp-proof course (DPC) or under concrete window sills. However, it's not typically used over cavity walls; cavity-type insulation should be used inside cavities, with XPS applied externally where cavity insulation isn’t feasible.

Is XPS insulation fire-safe?

XPS contains flame retardants but must not be exposed to open flames or ignition sources. Used within an external wall insulation (EWI) system, it is mechanically fixed, covered with mesh and basecoat and finished with render, meeting fire classification standards as part of the complete system.

EVOLUTION - Stress Plate Washer - 70mm (Box of 100)

Brand: Evolution

SKU: EVO-SPR70

£20.04 Incl. VAT

£20.04 Incl. VAT (regular price)

Please note: This product has a slightly longer lead time. Our team wiil notify you with an estimated delivery date.

Quantity:

EVOLUTION - Stress Plate Washer - 70mm (Box of 100)

The EVOLUTION SPR70 Stress Plate Washer is a robust and reliable solution for securing insulation, membranes and single-ply materials in flat roofing systems. Designed to distribute the load and reduce stress at the fixing point, this 70mm round stress plate helps prevent material from pulling over the fastener head. Manufactured with durability in mind, it ensures a firm and secure hold across a variety of roofing applications. Supplied in boxes of 100, it’s the go-to choice for professional roofing installations.

Diameter: 70mm
Thickness: 0.5mm
Quantity: 100 per box
Application: Flat roof insulation, membrane, and single-ply fixing

Frequently Asked Questions

The EVOLUTION SPR70 Stress Plate Washer is designed to secure insulation, membranes and single-ply materials in flat roofing systems. It distributes the load evenly around the fixing point, helping to prevent tearing or pull-over of the material.

The stress plate washer is used alongside compatible roofing screws or mechanical fixings. Simply position the washer over the fixing point before securing it through the insulation or membrane into the substrate below.

It is suitable for use with flat roof insulation boards, waterproof membranes and single-ply systems, ensuring a firm and secure hold across a wide range of roofing substrates.

Yes. The EVOLUTION SPR70 is designed to work perfectly with EVOLUTION Long Length Self Drilling Insulation Screws and other EVOLUTION fixing systems, ensuring a complete and reliable installation.

Stress plate washers help reduce stress concentration at the fixing point by spreading the load across a wider surface area. This improves fixing stability, prevents fastener head pull-through and extends the life of roofing membranes and insulation systems.