25mm Kingspan Kooltherm K103 Floorboard is a rigid thermoset phenolic floor insulation board, supplied here as a pack of 12 sheets covering 34.56m². The pack format suits whole-floor and full-room work, where a known floor area is being insulated in one go rather than topped up in sections: complete ground floors in new build, larger refurbishments, and beam-and-block or concrete slab floors taken across the full footprint.

Each board in the pack measures 2400mm x 1200mm and covers 2.88m², so the 12-board pack gives 34.56m² of coverage to plan a floor layout around. The phenolic core runs at a thermal conductivity of 0.019 W/mK, with a thermal resistance of 1.30 m²K/W at 25mm and a compressive strength of 120 kPa for screed and normal floor loads. Both faces carry a glass tissue based facing, autohesively bonded to the core during manufacture. As the slimmest board in the range, the 25mm covers area while adding the least depth to the build-up.

Across a larger floor the boards are loose-laid break-bonded with joints lightly butted, and on a multi-layer build-up the second layer is offset so that joints in adjacent layers do not line up. Cutting is done with a fine-toothed saw or by scoring and snapping. Buying the full pack means the boards for a run arrive together, so coverage and offcuts can be set out across the whole area at once rather than ordered again part way through.

25mm Kooltherm K103 is installed below the screed, below the slab or between the joists, depending on whether the floor is beam and dense block, solid concrete or suspended timber. It is laid over a damp proof membrane, fitted in line with Kingspan's guidance and the project specification, and is not installed directly over timber joists. The pack suits new build and refurbishment across domestic, commercial and industrial floors, and works with underfloor heating systems.

Key Benefits of Kingspan Kooltherm K103:

• Pack of 12 boards covering 34.56m², for whole-floor and larger-area work.
• 25mm rigid thermoset phenolic floor board, the slimmest profile in the K103 range.
• Lambda of 0.019 W/mK, among the lowest thermal conductivity figures for rigid floor insulation.
• R-value of 1.30 m²K/W at 25mm.
• 120 kPa compressive strength, taking screed and normal floor loads.
• Glass tissue facing both sides, autohesively bonded to the core in manufacture.
• 2.4m x 1.2m boards at 2.88m² each, giving 34.56m² of planned coverage per pack.
• Loose-laid break-bonded across beam and block, suspended timber and solid concrete floors.
• Keeps a larger job on one product line and one delivery, ordered by floor area.
• Works with underfloor heating, and suited to new build and refurbishment.

Good to know:

• A damp proof membrane (minimum 1200 gauge polythene) is required beneath the boards, and they should not sit in direct contact with subsoil.
• Although it resists the passage of water vapour, the board is not a vapour control layer; under a screed, lay a separate lapped and taped polythene sheet over it to act as the VCL.
• The boards are not fixed directly over timber joists; in a suspended floor they drop between the joists onto battens, saddle clips or nails.
• The 1.30 m²K/W resistance at 25mm suits whole-floor upgrade, top-up and multi-layer build-ups; run the full floor calculation against your target U-value before ordering pack quantities.

Only covering a small or part-finished area? This board is also available as single sheets: view single sheets.

For a whole floor in one order, the pack puts 34.56m² of the slimmest K103 board on site together, ready to set out by area.