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Floor Underlay Guide

Why Underlay Matters

Underlay is not optional — it directly affects the feel, sound, thermal performance, and longevity of the finished floor. For carpet: underlay adds softness (bounce and comfort), extends carpet life by reducing wear from below, provides thermal insulation, and reduces impact sound transmission. Budget carpet on good underlay feels better than premium carpet on cheap underlay. For laminate: underlay absorbs subfloor imperfections (a flat surface is essential for click floors — any high spots tran

Underlay Types and Tog Values

Carpet underlay is rated by tog value (thermal resistance) and density (kg/m³): standard 9mm (10mm Cloud 9): 2.5 tog — good general purpose. Premium 11mm (memory foam or high-density rubber): 3.5 tog — maximum comfort and longevity. High thermal underlays (3.5-4.0 tog) are required for carpet over underfloor heating systems as the system must push heat through the underlay efficiently. Laminate underlay: basic foam (1.5mm, grey): minimum viable, no acoustic benefit. Combined acoustic/vapour barr

Gripper Rod Installation

Gripper rod is a thin strip of wood with angled tacks that grip the underside of the carpet, holding it taut and preventing movement. Install gripper rod approximately 6-8mm from the skirting board on all perimeter edges (the gap allows the carpet to be tucked down behind the skirting). Nail to the floor every 300mm. At doorways: use a metal threshold bar rather than gripper rod. Fit underlay within the gripper rod perimeter, butting right up to the rod without overlapping it. Staple or tape und

Dealing with Subfloor Issues

The most common installation failure: uneven subfloor. Laminate and LVT over a subfloor with humps, dips, or edges that exceed the manufacturer's tolerance (typically ±3mm per 1.8m) will creak, develop gaps, or crack at the locking joints. Prepare the subfloor before installing: concrete — use a self-levelling compound to fill dips. Timber floorboards — ring-shank nails (not screws) to stop squeaks, fill wide gaps with flexible filler, consider 6mm plywood overlay for very uneven boards. Hardboa