25mm Polystyrene Insulation

25mm polystyrene insulation boards sit at one of the most practical points across the full thickness range. Slim enough to suit shallow build-ups and restricted floor zones, but thermally effective for a wide range of standard residential and commercial applications. At this depth, polystyrene insulation sheets are regularly specified below ground-floor slabs, within floor build-ups finished with chipboard or screed, and in below-ground applications where a compressible layer is required. Lightweight and easy to cut on site without any need for specialist tools, they are a practical choice wherever speed of installation matters.

For the applications they are designed for, 25mm polystyrene insulation boards perform reliably and consistently. Whilst polystyrene does not offer the same thermal conductivity as higher-performance materials such as PIR or phenolic, it more than holds its own as a cost-effective rigid board insulation with good compressive strength and solid moisture resistance. At 25mm, it is a trusted specification for standard floor build-ups and below-ground applications where those properties matter most.

Our 25mm polystyrene insulation range is supplied by Jablite and SPI and covers three distinct product types, each suited to different project requirements.

Types of 25mm Polystyrene Insulation

Standard EPS boards are white expanded polystyrene boards available across a wide range of grades to suit different compressive strength requirements, from standard domestic floor slabs through to heavy commercial and industrial applications.

Grey EPS High Performance Plus boards are graphite-enhanced grey EPS boards that offer better thermal performance at the same thickness as standard white EPS, suited to floor build-ups where a lower U-value is needed without increasing board depth.

Clay Heave boards are a specialist compressible EPS product designed to protect foundations from ground movement caused by expanding and contracting clay soils.

Applications for 25mm Polystyrene Insulation

Floor insulation is the most common application for 25mm polystyrene insulation boards. Whether the board is going below a concrete slab, above the slab below chipboard, or above the slab below screed, there is a product and grade within this range to suit the load and the spec, including specialist clay heave boards for below-ground and foundation protection on clay-heavy ground.

All boards are easy to cut on site using a fine-tooth saw or hot-wire cutter with no specialist PPE required. Where a project needs greater thermal performance from a single layer, we stock polystyrene insulation sheets from 50mm right through to 100mm and above, so there is always a solution to suit.

Why Choose Insulation UK for 25mm Polystyrene Insulation?

A comprehensive range in stock across standard EPS, high performance grey EPS, and clay heave boards at 25mm, covering everything from standard domestic floor slabs through to specialist below-ground applications.

Products from trusted manufacturers including Jablite and SPI, all available at competitive trade prices with no minimum order value.

Fast UK-wide delivery with free shipping on orders over £500 (ex VAT), and reliable nationwide logistics on every order despatched from our distribution centre in Rotherham.

Competitive pricing with some of the lowest 25mm polystyrene insulation prices available online, backed by strong stock availability and a trusted supply chain.

Expert help and advice from a team with over 50 years in the industry. Whether you are selecting the right EPS grade for a domestic floor slab, choosing between standard and high performance grey EPS, or specifying clay heave protection for a below-ground application, we are here to make sure your project runs smoothly from start to finish.