XPS Insulation

Buy XPS insulation boards online from Insulation Wholesale. We stock and supply XPS boards suitable for floors, inverted roofs, and ground-bearing slabs in trade quantities as well as smaller orders. Our team can help you choose correctly, especially where XPS is required by design (below slab, inverted roofs, high load areas). We provide fast quotes with nationwide delivery.

Bulk discounts on XPS insulation are mainly offered by trade-focused suppliers. Most general builders’ merchants do not consistently stock XPS and rarely offer significant discounts. Some regional trade counters may offer discounts, but stock levels and brands vary. At Insulation Wholesale, we offer price breaks on higher quantities, mixed-thickness orders, and repeat trade purchases.

XPS is one of three common rigid foam boards used in the UK. Each suits different conditions.

XPS (Extruded Polystyrene)

• Very low water absorption
• High compressive strength
• Performs well below ground and in wet zones
• Slightly higher thermal conductivity than PIR (typically ~0.029–0.036 W/m·K)

PIR (Polyisocyanurate)

• Better thermal performance per millimetre
• Lighter and easier to cut
• Not suitable for constant contact with moisture
• Common in walls and warm roofs

EPS (Expanded Polystyrene)

• Cheapest option
• Lower strength and higher water uptake than XPS
• Used where loads and moisture are limited

Use XPS where strength and moisture resistance matter.
Use PIR where thickness is limited.
Use EPS where cost matters most.

How to install XPS insulation?

XPS installation depends on location, but the basics are the same:

• Prepare the surface 

The substrate must be flat and debris-free. Any rocking boards will cause problems later.

• Lay the boards tightly 

Place XPS boards tight-jointed, staggering joints like brickwork. This improves load spread and reduces cold paths.

• Fix or restrain correctly 

• Floors / below slab: Boards are usually loose-laid beneath concrete.
• Inverted roofs: Boards are loose-laid over waterproofing and held down with ballast.
• Walls: Use mechanical fixings or compatible adhesive, depending on system design.

• Protect edges and joints 

Some systems require taped joints or edge upstands to limit water tracking. Follow the project details.

• Apply a load-spreading layer 

Concrete, screed, or protection boards must be installed as specified to evenly distribute loads.

Some inverted roof systems also use a filter membrane above the XPS before the ballast layer is added.