Closed Cell XPS Foam Board 50 mm Rigid Panel For Inverted Roof Thermal Insulation

The RF250 board is built for the inverted roof, the one position where insulation is exposed above the waterproofing membrane and must survive ballast, paving and service traffic. At 50 mm and 250 kPa it carries the weight of slabs and gravel while holding the membrane at a stable temperature. The closed cell body is the reason the assembly works: water does not pass from cell to cell, so the membrane below stays dry and the insulation can be lifted, stored and refitted when the membrane is repaired.

Continuous extrusion gives the board a dense skin on both faces and an even cell size through the thickness, which is why the declared conductivity holds across the full 30 to 140 mm range and why the board keeps its 250 kPa compressive strength after the edges are shiplapped. Shiplap edges let adjacent boards overlap rather than butt, so the joint stays tight when the assembly moves under thermal load. The RF250 XPS foam board is supplied in standard sizes of L 1200 / 2400 mm, W 600 / 1200 mm, THK 30 - 140 mm, and the board can be cut on site with a fine toothed saw or a hot wire, which keeps the cut face closed.

Technical Data

Applications

Specified wherever the insulation layer is above the membrane and the finished surface carries load.

• Inverted flat roofs above the waterproofing membrane
• Terrace roofs, balconies and accessible podium decks
• Pitched roofs with rafter level external insulation
• Ballasted and paved roof assemblies
• Green roof drainage and filter layers
• Membrane protection where slabs are laid dry

Key Advantages

• Closed cell structure limits water uptake to 1.5% by volume, so conductivity stays stable in service.
• 250 kPa compressive strength suits ballast, paving slabs and foot traffic on the finished roof.
• Service range of -50 to 75 C covers both winter surface temperatures and summer solar gain on dark finishes.
• Shiplap edges reduce thermal bridging at board joints.
• Boards can be lifted and reused when the membrane below is opened for repair.

The Closed Cell 250 kPa XPS Foam Board is produced on the same continuous extrusion line as the rest of the RF250 range, so the cell structure and the declared figures do not change from order to order. Buyers who compare grades will find the Closed Cell 250 kPa XPS Foam Board in the RF250 band, where the compressive strength and the thickness are fixed by the load case rather than by the price.

Installation Notes

• Boards are laid with joints staggered and edges fully engaged over the whole face.
• Surfaces in contact with adhesive or membrane are cleaned and primed before the board is bedded.
• Boards are cut oversize by 10 mm where a tight fit into a frame or reveal is needed, then trimmed.
• Finished layers are protected from site traffic until the covering layer is in place.

FAQ