UltraFloor Level IT Flex is recommended for use over plywood as thin as 6mm due to its flexural capacity. Wooden floors vary from traditional wooden floorboards, plywood, chipboard and other wood composites. Wooden substrates exhibit an element of flexibility. Preparation is of vital importance! If the wooden floor is not rigidly braced, any deflection exhibited in the floor may cause stresses to build up, and any consequent stresses placed on the flooring may cause cracking. We recommend that the plywood be fixed and screwed at 300mm centres, and primed thoroughly using UltraFloor Prime IT Multi-surface Primer.