If you want to fit our engineered oak plank flooring over underlay (known as 'floating' the floor) and do not need to specifically reduce sound transmission or accommodate underfloor heating, we recommend Fibreboard.
Made from recycled natural fibres, it is environmentally responsible, and as it is already compressed, does not compress further over time as you walk on it. It also reduces impact sound transmission by 19dB. (This product is not designed specifically to reduce sound transmission, but a 10dB reduction is considered to halve audible noise levels.)
Fibeboard underlay is supplied in packs of 20 sheets of 850mm x 590mm x 5mm (10.3m2 per pack).