Why the Right Underlay Makes a Real Difference

Underlay is one of the most overlooked elements of any flooring installation - and one of the most consequential. Lay the wrong underlay, or skip it entirely, and even a premium floor covering will feel hard underfoot, transmit impact noise to the floor below, and fail to perform to its thermal potential. Choose the right underlay and the floor above it feels more comfortable, sounds quieter, insulates better, and lasts longer. The underlay is not a secondary purchase - it is a direct determinant of how good your finished floor actually feels and performs in daily use.

The CorkSystem underlay range is built around XPS - extruded polystyrene - and specialist LVT formulations, each selected for specific performance characteristics and flooring compatibility. XPS underlays offer excellent compressive strength, consistent thermal resistance, and reliable acoustic performance across a broad range of thicknesses. LVT and vinyl underlays address the specific demands of rigid and flexible luxury vinyl tile systems, where dimensional stability and high-density construction are critical to a flat, stable, and durable installation.

XPS Underlays - Thermal Insulation for Laminate and Wood Flooring

XPS underlays are the most versatile option in the range and suitable for the widest variety of laminate and engineered wood flooring applications. CorkSystem stocks XPS underlays in 2mm, 3mm, 5mm, 6mm, and 10mm thicknesses, giving you precise control over the level of thermal and acoustic performance your installation requires.

XPS 2mm Roll Underlay with ALU Membrane covers 16.5 m² per roll and is available from £32.99. The aluminium membrane adds a vapour barrier function and enhances thermal reflection, making this a particularly capable option for ground floor and below-grade installations where moisture management is important alongside insulation performance.

XPS 3mm Underlay is available from £9.99, covering between 12 and 48 m² depending on the pack selected. A standard 3mm XPS underlay is one of the most commonly specified options for laminate flooring in the UK - it provides a meaningful improvement in thermal comfort and impact noise reduction without adding significant height to the floor build-up. An XPS 3mm with Aluminium Membrane variant is also available from £27.99, adding enhanced vapour control and thermal reflectivity for more demanding subfloor conditions.

XPS 5mm Underlay is available from £12.99, covering 7 to 49 m² per pack. At 5mm, the thermal and acoustic performance increase is noticeable compared to the 3mm option, and this thickness is particularly well suited to rooms where acoustic comfort is a priority - upper floor installations in multi-storey homes, flats, and rooms above garages or utility spaces. The XPS 5mm with Aluminium Membrane variant is available from £22.99, and the Underlay Quick XPS 5mm - a fast-lay format designed for efficient installation on larger projects - is available from £14.99.

XPS 6mm Underlay steps up performance further, available from £14.99 and covering 5 to 50 m² per pack. For rooms where the subfloor has minor surface irregularities, 6mm XPS provides a more forgiving base layer, helping to bridge small imperfections and maintain a consistent surface level across the finished floor.

XPS 10mm Underlay is the highest-performing option in the standard XPS range, priced at £22.99 for a 4.8 m² pack. At 10mm, this underlay delivers the maximum thermal insulation and impact noise reduction available from an XPS product - making it the right choice for ground floor installations in older properties, rooms that are difficult to heat, and any project where comfort underfoot is the primary specification criterion.

XPS Underlays for Underfloor Heating

Not all underlays are compatible with underfloor heating systems. An underlay that is too thick or has too high a thermal resistance will impede heat transfer from the heating element to the room above, reducing efficiency and increasing running costs. CorkSystem's Underlay XPS Thermo-Laminate at 2.5mm is specifically designed for use with underfloor heating systems beneath wood and vinyl flooring, available from £11.49 and covering 6 to 42 m². Its low thermal resistance allows heat to pass through effectively while still providing a degree of acoustic cushioning and surface stability. Always check your underfloor heating manufacturer's maximum underlay thermal resistance specification before selecting an underlay for a heated floor installation.

LVT and Vinyl Underlays - Specialist Performance for Rigid and Flexible Vinyl

Luxury vinyl tile and plank flooring - whether rigid click LVT or flexible sheet vinyl - has specific underlay requirements that differ from laminate and wood. LVT systems are dimensionally rigid and highly sensitive to subfloor irregularities. An underlay that is too soft or compressible can cause click joints to flex and fail over time. The right LVT underlay provides a high-density, stable base that supports the floor system evenly without introducing movement.

Professional LVT Underlay (Vinyl) 1.5mm is available from £15.99, covering 6 to 42 m². High-density construction provides the firm, stable base that LVT requires, while the 1.5mm thickness keeps the floor build-up minimal - important in rooms with fixed door thresholds or fitted furniture.

SilverLux 1.5mm LVT Underlay with Silver Membrane and GoldLux 1.5mm LVT Underlay with Gold Membrane represent the premium end of the LVT underlay range, priced at £47.49 and £52.99 respectively. Both are super high-density products offering the best combination of dimensional stability, acoustic performance, and membrane protection available in this format. The silver and gold membrane variants provide enhanced vapour control and thermal reflectivity - the right choice for premium LVT installations where long-term performance is the priority.

Minerals and Polyurethane (PU) Underlay with ALU Membrane at 1.8mm is the highest-specification product in the entire underlay range, available at £55.99 for 10 m². Constructed from a mineral and polyurethane composite with an integrated aluminium membrane, this underlay is designed for vinyl, wood, and laminate installations where maximum acoustic performance, vapour control, and underlay longevity are required. It is the professional installer's choice for premium flooring projects where no compromise is acceptable.

Vapour Barrier Foil - Essential Moisture Protection

For installations over concrete subfloors, ground-bearing slabs, or any substrate where moisture vapour transmission is a risk, a vapour barrier is an essential addition to the underlay specification. CorkSystem's Vapour Barrier Foil covers 100 m² per roll at £39.99, providing a reliable and cost-effective moisture barrier for laminate flooring, plasterboard, insulation, and attic wall applications. Installing a vapour barrier beneath the underlay layer prevents moisture from migrating upward through the subfloor and into the floor covering - protecting both the underlay and the flooring above from the swelling, warping, and adhesive failure that moisture damage causes.

How to Choose the Right Underlay

Selecting the correct underlay for your project comes down to four key considerations: flooring type, subfloor condition, room location, and whether underfloor heating is installed.

• Flooring type determines whether you need a standard XPS underlay or a specialist high-density LVT product. Laminate and engineered wood work well with XPS underlays across the full thickness range. Rigid LVT and vinyl require the high-density LVT-specific products.
• Subfloor condition influences the thickness you should choose. A smooth, level concrete or chipboard subfloor is compatible with 2mm or 3mm underlays. A subfloor with minor surface variation benefits from 5mm or 6mm to bridge irregularities and maintain a consistent level.
• Room location affects whether a membrane is necessary. Ground floor, basement, and below-grade rooms benefit from aluminium membrane or vapour barrier products. Upper floor rooms in dry conditions can use standard XPS without a membrane.
• Underfloor heating requires a thin, low-resistance underlay - the 2.5mm Thermo-Laminate is the correct choice for heated floor systems.

FAQ - Underlays

Q: What is the difference between XPS underlay and LVT underlay?
A: XPS underlays are made from extruded polystyrene and are designed for use beneath laminate and engineered wood flooring. They provide thermal insulation, acoustic cushioning, and a degree of surface levelling. LVT underlays are high-density specialist products designed for luxury vinyl tile and plank systems, which require a firmer, more dimensionally stable base. Using a soft or compressible underlay beneath rigid LVT can cause click joints to flex and fail over time - always use an LVT-specific underlay for vinyl flooring.

Q: Do I need an underlay with an aluminium membrane?
A: An aluminium membrane adds vapour control and thermal reflectivity to the underlay. It is particularly valuable for ground floor installations over concrete subfloors, rooms below grade, and any situation where moisture vapour transmission from the subfloor is a concern. For upper floor installations over dry timber or chipboard subfloors, a standard XPS underlay without a membrane is usually sufficient.

Q: Which underlay is compatible with underfloor heating?
A: The XPS Thermo-Laminate 2.5mm underlay is specifically designed for use with underfloor heating beneath wood and vinyl flooring. Its low thermal resistance allows heat to transfer effectively from the heating element to the room above. Always check your underfloor heating manufacturer's maximum underlay thermal resistance specification before selecting a product.

Q: What thickness of underlay should I choose for laminate flooring?
A: For most standard laminate flooring installations on a smooth, level subfloor, 3mm XPS is a practical and cost-effective choice. For rooms where acoustic performance is a priority - particularly upper floor installations in flats or multi-storey homes - 5mm or 6mm provides meaningfully better impact noise reduction. For maximum thermal insulation on ground floor or below-grade installations, 10mm XPS is the highest-performing option in the range.

Q: Do I need a separate vapour barrier, or is the membrane on the underlay sufficient?
A: Many XPS underlays with aluminium membranes provide a degree of vapour control, but for high-risk subfloors - particularly freshly laid concrete, older solid floors, or any subfloor where moisture readings are elevated - a dedicated vapour barrier foil laid beneath the underlay provides a more complete level of protection. Our Vapour Barrier Foil covers 100 m² per roll and can be used in combination with any underlay in the range.

Q: Can I use the same underlay for both laminate and LVT flooring?
A: No - laminate and LVT have different underlay requirements. Standard XPS underlays are designed for laminate and engineered wood, where some degree of cushioning and compressibility is acceptable. LVT requires a high-density, low-compressibility underlay to support the rigid click system. Using a standard XPS underlay beneath rigid LVT can compromise the long-term integrity of the click joints.

Q: How do I calculate how much underlay I need?
A: Measure the total floor area of the room in square metres. Select the underlay pack size that matches or exceeds your floor area - most products in the range are available in multiple coverage options to minimise waste. Add 10% for cuts and wastage, particularly in rooms with alcoves, bay windows, or irregular shapes.

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