To prepare for hardwood flooring, remove the existing flooring and the baseboards, and measure the door casings to ensure the flooring fits under the casing. Cut the casings upward from the floor if necessary, and clean the floor thoroughly. Use a moisture meter to determine whether the subflooring is suitable for hardwood flooring, nail down any loose boards, and lay out the moisture barrier if it is required.
Nail-down and floating hardwood flooring can be installed directly over vinyl flooring, provided the vinyl is one to two layers thick. If another type of flooring is present, such as carpet, remove it and use a sander to clean the subfloor. Sweep or vacuum the floor after sanding to remove dust.
When measuring the door casing, stack a small piece of the moisture barrier, underlayment and a plank of the flooring together, and slide the stack under the door casement. Cut the door casing upward by 1/16 to 1/8 inch if the stack of flooring materials doesn't easily slide under it.
Refer to the manufacturer's guidelines to determine whether the moisture levels of the subfloor are appropriate for the flooring, and take measurements of both the wood and concrete if a plywood subfloor is installed over a concrete slab. The manufacturer's specifications also state whether a moisture barrier is necessary when installing wood flooring.