Finishing Hardwood Floors 4 - Prepping the Floor Finishing Hardwood Floors 4 - Prepping the Floor

Margin of Error: Not applicable

Most Common Mistakes

  1. Not setting nail heads below floor level.
  2. Not removing shoe molding.

Before beginning your sanding work, some prep work will probably be in order. Take a close survey of the floor. Note if any pieces are so badly damaged that they need to be replaced. Note where there are any nail heads above the level of the flooring. These will have to be countersunk with a nailset and hammer, or they will tear the sandpaper. Remove the shoe molding where the floor meets the wall. Try to remove this gently so that it can be reused and nailed back into place, once the refinishing is completed. Also, note where there are any bad ridges or cupped boards, because these areas will take extra sanding. Finally, before sanding, sweep and vacuum the floor well, and seal off the room from the rest of the house so that dust will not spread. You may even want to consider using plastic and tape around the edges of all doors leading into other areas of the house.

Repairing Squeaky Boards

Squeaky boards are annoying, but often can be easily fixed. Try fixing them with the simplest technique: inserting a shim from below the floor, between the floor joist and the area where the floor is squeaking. Sometimes, even tapping the squeaking area with a hammer and 2 x 4 wrapped in a towel will work. Also, try squirting some lubricant such as graphite, talcum powder, floor oil, mineral oil, or wood dough between the boards. You can even try forcing metal glazier's points between the boards every 6" to separate the boards.

If these simpler techniques are not working, try drilling a pilot hole through the board, nailing from above with a finishing nail, and then countersinking the nail and filling the hole with wood dough. This technique also works for repairing cupped or warped boards. If the floor joists are exposed from below, you can drill a pilot hole up through the floor joist and/or subflooring and 1/4" into the squeaky board. A drill bit stop will be useful here to prevent drilling through the floor surface.

Wrapping masking tape around the bit will work as a drill guide. Then you can grab the board from below with a 3/16" roundhead wood screw with a large washer. This technique of screwing the flooring from below also works when repairing cupped or warped boards. One other possible solution is to add metal joist bridging or wood blocking between the joists near the squeak. This will often stiffen the floor and eliminate the squeak

Badly Warped or Cupped Floors

Some floors may be badly warped or cupped, due to moisture. In this case it is not practical to repair each board individually. Instead, I recommend you sand the entire floor down to an even level. Use your drum sander and a rough grade of sandpaper and make diagonal passes across the cupped areas until they are all smooth and level. Later you will have to sand with the grain in order to work out all the unsightly sanding marks left by the diagonal sanding.

Damaged Boards

Badly marred or damaged boards often need to be replaced. You will need to cut and chisel these out of the floor and replace them with new boards. To do this, adjust the blade on your circular saw to the thickness of the damaged floor to avoid cutting the subfloor. Use a plunge cut and saw down the center of the board, taking care not to cut into the good boards at either end.


Using a hammer and chisel and a pry bar, remove the damaged board, again taking care not to mar any adjacent boards. Cut a new piece the exact length and remove its tongue so that it will fit into the opening. Also chisel off the tongue of the board protruding into the space. Install the new board, applying two 1/4" beads of subfloor adhesive to its bottom, and insert it into the opening. Finally, pre-drill pilot holes through the new board into the subfloor and nail the board with finishing nails. Countersink these nails and cover with wood dough.



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