To maximise the life of the carpet, it is essential to lay a new underlay below any new fitted carpet. In addition to prolonging the life of the carpet, underlays provide a more comfortable tread, and improve thermal and acoustic insulation. Carpet underlay is usually made of sponge rubber, foam, or crumb rubber. Crumb rubber is manufactured from re-cycled car tyres. Underlay is also used below wood and laminate floors, to provide a firm fit and avoid creaking.