Finishing and Maintaining Wood Floors
Part 3 – Old Surface Preparation

Sanding

If an old finish cannot be satisfactorily repaired, a complete sanding of the surface and then application of a new finish may be necessary.  Most flooring is ¾-inch thick so it can withstand a number of sandings.  In these cases, make certain that all nails are countersunk and that the floor is as clean as possible before sanding.  Use an “open face” paper to remove the old finish.  The heat and abrasion of the sanding operation may make the old finish gummy and will quickly clog normal sandpaper.  Once new wood appears, regular sandpaper may be used. 

Condition of Floor

The number of cuts required to restore an old floor is largely determined by the condition of the floor and the thickness of the finish being removed.  If the floor is badly scarred or warped, use as many cuts as necessary to get a smooth, unblemished surface.  Make the first one or two cuts at a 45 degree angle with medium grit paper, and then follow the instructions given for sanding a new floor.  If the surface is in good shape and has no thick build-up of old finish and wax, one pass with the disk sander and extra-fine paper may be sufficient.  Just be sure that you have removed all the old finish.

Old finishes may also be removed with a non-aqueous (no water) varnish remover, after which the floor should be sanded as for new flooring.   This is a great time saver!  If the floor is less than ¾-inch thick or if it is made from hardwood plywood, care must be exercised to prevent sanding through to the less desirable wood underneath.  The floor thickness can usually be determined by removing a floor heating register or the shoe mold and baseboard so that an edge of the floor is exposed.  This is assuming that the floor is of uniform thickness.  When refinishing these floors a chemical varnish remover may be useful.  It will also help to use a floor polisher or disk sander rather than the drum sander.  Do not remove more wood than absolutely necessary.