50mm Polystyrene Insulation

50mm polystyrene insulation boards are one of the most widely specified thicknesses across UK construction, and it is not difficult to see why. Thick enough to deliver meaningful thermal performance as a standalone layer in a wide range of floor, roof, and below-ground applications, yet practical and straightforward to handle and cut on site, 50mm sits at a point where performance and usability meet. Polystyrene insulation sheets at this thickness are regularly specified below ground-floor slabs, within screed and chipboard floor build-ups, in inverted and flat roof applications, and wherever superior moisture resistance or high compressive strength is required.

For the applications they are designed for, 50mm polystyrene insulation boards perform reliably and consistently. Whilst polystyrene does not offer the same thermal conductivity as PIR or phenolic, it delivers strong performance relative to its cost, with good compressive strength and solid moisture resistance that makes it a trusted specification across both domestic and commercial projects. The U-value achieved will always depend on the full build-up rather than the board alone, but at 50mm polystyrene boards make a meaningful contribution to thermal performance across all the applications covered by this range.

Types of 50mm Polystyrene Insulation

EPS boards are available in standard white EPS, high performance graphite-enhanced grey EPS, and specialist clay heave boards, covering everything from standard domestic floor slabs through to foundation protection on clay-heavy ground. Browse the full EPS range on our EPS insulation page.

XPS boards from Kingspan GreenGuard and Ravatherm offer superior compressive strength and moisture resistance, suited to below-ground, inverted roof, and moisture-exposed applications. Browse the full XPS range on our XPS insulation page.

Applications for 50mm Polystyrene Insulation Boards

Floor insulation is the most common application for 50mm polystyrene insulation boards. Whether below a concrete slab, above the slab below screed, or above the slab below chipboard, there is a product and grade within this range to suit the load and the spec, including specialist clay heave boards for foundation protection on clay-heavy ground and XPS boards where load-bearing requirements or moisture exposure are more demanding.

Beyond floors, 50mm polystyrene insulation sheets are also used in inverted and flat roof build-ups, below-ground basement applications, and perimeter insulation around floor slabs. All boards are easy to cut on site using a fine-tooth saw or hot-wire cutter with no specialist PPE required. Where greater thermal performance or a different thickness is needed, we stock polystyrene insulation boards from 25mm right through to 100mm and above, so there is always a solution to suit.

Why Choose Insulation UK for 50mm Polystyrene Insulation?

A comprehensive range in stock across EPS and XPS at 50mm, covering everything from standard domestic floor slabs through to specialist below-ground and high-load applications.

Products from trusted manufacturers including Jablite, SPI, Kingspan and Ravatherm, 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 50mm 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, deciding between EPS and XPS for a moisture-exposed application, or specifying clay heave protection for a below-ground build, we are here to make sure your project runs smoothly from start to finish.