Underlay is typically used to assist in lessening noise and act as a buffer for insulation. An underlay is recommended to reduce the chances of your engineered or laminate flooring expanding, contracting, or cupping.
Engineered wood and certain laminate flooring are good for use with under-floor heating due to their elasticity.
You won't have to fill any knots in most new solid or engineered wood floors because of the great quality of the finish. In cases where filling in knots in the flooring is necessary. Unfortunately, knots can often develop into holes, which presents an entirely new set of challenges. Fibreglass resin combined with Hydroxide Activator and some black resin pigment can seal knots in flooring and produce an attractive two-tone effect. Fill the cracks slowly to allow air to rise to the top, then come back in 30 minutes if necessary to apply a second coat.
Because wood expands and contracts according to the relative humidity in the air, an expansion gap is required. In the case of wood floors, expansion happens against the grain, so the width grows rather than the length. This and other information can be found in our cupping guide and our reference to caring for and installing your wood floor.