Do I need underlay for my flooring?
It depends on the flooring type. Laminate almost always needs underlay — it provides cushioning, sound dampening and a moisture barrier. Hybrid / SPC flooring often comes with pre-attached underlay — check before buying separately, as doubling up causes instability. Engineered timber benefits from underlay for sound and comfort. Carpet always needs an underlay (also called a carpet cushion or carpet underlay) — it dramatically affects carpet feel and longevity.
Types of underlay
- Foam underlay — the most common and affordable. Good for laminate and some hybrid flooring. Comes in 2 mm, 3 mm and 5 mm thickness.
- Rubber / cork underlay — better sound dampening, more durable. Good under timber and high-traffic areas.
- Combination underlay with vapour barrier — foam with a plastic film layer. Essential for concrete subfloors where moisture is a concern — very common in Queensland.
- Carpet underlay — foam or rubber chip. Thickness affects carpet feel; 10 mm is standard for residential, 8 mm for commercial.
Thickness — does it matter?
For floating floors (laminate, hybrid), 2–3 mm is the typical recommendation. Thicker underlay can cause floating floors to flex too much, stressing the click-lock joints. Check your flooring manufacturer's specification — many specify a maximum underlay thickness (often 3 mm) to keep the warranty valid.
Concrete subfloors — moisture is critical
In Queensland and coastal Australia, concrete subfloors almost always need a moisture barrier. Use a combination underlay with an integrated vapour barrier, or lay a separate 200-micron poly film before the underlay. Skipping this step is the most common cause of flooring failure in Australian homes.
Standard roll sizes in Australia
Underlay rolls at Bunnings, Carpet Court and flooring suppliers are typically sold in 10 m², 15 m² and 20 m² rolls, usually 1 m wide. Some premium products come in wider rolls. Always check the roll dimensions on the packaging — this calculator uses the m² per roll you select.