After cleaning a sub-floor where oak strip flooring will be installed, what is the first step?

The appropriate first step after cleaning a sub-floor before installing oak strip flooring is to lay down #15 asphalt coated paper. This underlayment plays a crucial role in flooring installation, providing moisture protection and preventing the wood from absorbing moisture from the sub-floor, which helps to minimize the risk of warping or damage to the flooring over time. The paper also serves as a separation layer that can reduce noise and serve as a barrier against dust and other contaminants that may affect adhesion or the flooring’s longevity.

The other options might seem relevant at various stages but are not the immediate first step after cleaning. Immediately installing the flooring without proper preparation could lead to issues with moisture and adherence. Applying adhesive would also be premature, as it should follow the laying of the underlayment. Finally, measuring and marking layout lines is essential for ensuring proper alignment during the installation, but this step typically occurs after the underlayment has been placed, not immediately after cleaning the sub-floor.