Underlay is often treated as an afterthought, but it plays a significant role in how your floor feels, sounds and lasts. The wrong underlay can void a manufacturer warranty. Here is what to consider.
Underlay for laminate and engineered wood
Most laminate and engineered wood products are laid floating, which means a good foam or rubber underlay is essential. Key specifications:
- Thickness: 3mm is a good minimum. Thicker underlay feels better underfoot but check the product’s maximum recommended thickness — too thick can stress click joints.
- Moisture barrier: On concrete or a ground floor, choose an underlay with an integrated damp-proof membrane (DPM).
- Acoustic rating: Above another flat or room, look for high impact sound reduction (ΔLw) rating.
Underlay for carpet
Carpet underlay is measured in tog (thermal resistance) and density (kg/m³). Choose higher density (130–160 kg/m³) for heavy-use areas and stairs. A tog rating of 2.5–3.5 is suitable for most bedrooms and living rooms.
Underlay for LVT
Many LVT products have underlay pre-attached. If yours does not, use a specialist thin-profile LVT underlay (typically 1.5–2mm). Do not use standard thick foam underlay under LVT — it can cause click joints to flex and fail.
Underlay and underfloor heating
If fitting over underfloor heating, choose a low tog underlay — ideally below 1.0 tog. High tog underlay acts as insulation and significantly reduces heating efficiency.
Your flooring fitter will recommend the right underlay for your specific product and subfloor. Getting it right from the start is always cheaper than fixing problems later.