Once the unfinished flooring materials are installed you will prepare the floor for finishing. The first step is sanding the surface smooth. You can rent a hardwood floor sander by the day from larger flooring or rental stores. Or you may opt to hire an experienced floor sander to do the job. It’s very messy work so make sure all furniture in the work space is removed or covered.
Sanding unfinished hardwood flooring typically requires four passes with a large pad or belt floor sander. The first pass is with a medium grit to rough up the surface. Then take a pass with coarse, medium, and fine grit papers. Make sure you wear a respirator and goggles to keep sand out of your lungs and eyes. Wearing a painter’s cap is a good idea, too.
Floor sanding paper (rolls or sheets) come in five grades: very coarse (20-30 grit), coarse (36-40 grit), medium (50-80 grit), fine (100-120 grit), and very fine (150 grit). If the installed surface is relatively smooth and all you need to do is level the joints, start with coarse or medium grades then step down to the next finer grade with each sanding. Start in one corner of the room and make sure that each row you sand overlaps the last.
Sanding an unfinished hardwood floor is done in two steps: a large drum or pad sander is used for most of the room and an edge sander is used for the edges. The edge sander is required because the larger sander can’t safely and efficiently reach the 6 in. of flooring material closest to walls.