Maintaining and Recoating Polyurethane Wood Floors
by Hal Rusche, 2nd of Heritage Hardwood Floors
Can polyurethane floors be recoated?
Yes, a polyurethane-finished hardwood floor may have additional coats of polyurethane applied.
1. Lightly sand with a dull 120 to 150 grit abrasive screen or #2 steel wool under a heavy floor buffer.
2. Hand sand corners, edges and under cabinet kick plates.
3. Sweep up dust with a broom then vacuum clean the whole floor well.
4. Run a damp tack cloth over the floor to pick up what the others have missed. Dampen cloth with water, formulated floor cleaner or paint thinner.
5. Coat the edges of the floor with a brush and then do the center of the floor with a natural lamb's wool applicator. Always apply finish with the grain direction. On a parquet floor the grain direction doesn't matter.
If you are using water-based polyurethane...
If you are using oil-based polyurethane and would like a very thin coat then use a synthetic paint pad instead of a lamb's wool applicator. Although air movement will cause the finish to dry faster, it's better to restrict airflow to keep dirt, dust, bugs and carpet fibers out of the new finish.
Regular maintenance will prolong the life of your floor!!
Keep the floor clean, use furniture floor protectors and expect to apply a new coat of polyurethane on the floor every five to seven years. Usually there is little or no loss of polyurethane and no danger of damage to the wood floor after only five to seven years of use. But there are normally enough scratches, dings, dents and dull spots to warrant an additional coat of polyurethane on the floor for cosmetic reasons. If your floor looks good you need not coat it, if your floor is showing wear, you need not wait, do it now.
When we sand through finish a hardwood floor, we always apply the minimum two coats of polyurethane. If the floor-owner wants more polyurethane on the floor, we will suggest they get some wear and tear out of the first two coats before more is applied. No matter how many coats of polyurethane are on the floor, it's the top one that takes the beating and the floor will still need an additional coat of polyurethane in five to seven years. This is the industry standard.
A © inch thick hardwood floor has a wear surface, the thickness above the tongue, of a little over © inch thick. This thickness will allow the floor to be totally sanded to the wood twelve times. If the floor is sanded to the wood twelve times and each sand job lasts fifty years, then the floor will last for six hundred years. Whereas if you sand to the wood every five to seven years the life of the floor is shortened to sixty to eighty five years.
Note from NH: Some old, damaged floors may need so much work that it's wise to look into floor replacement as an alternative.
Never use wax, oil soaps, or other coatings on your polyurethane floor!!
Since coating the floor with polyurethane occasionally is expected, you must always be careful never to apply anything that will interfere with a future touchup of the finish. Never use wax, oil soap or acrylic floor dressings, such as Mop & Glow, on your polyurethane finished wood floor. Just vacuum your wood floor often, wipe up spills as they happen and occasionally damp mop with water. Or better yet, use a formulated hardwood floor cleaner with a special hardwood floor mop to minimize the amount of water that the wood floor is subjected to.
A common reason that a flooring contractor won't coat a used wood floor with an additional coat of polyurethane is that very often the floor-owner can't guarantee that the floor has never been treated with something that will inhibit a new coat of polyurethane from adhering to the existing finish.
Too many coats of polyurethane are not good!
Although each additional coat of polyurethane applied to the floor makes the floor easier to clean, it also changes the way that the floor looks. If you like the way that your floor looks with only two coats of polyurethane on it, then you may be surprised by the resulting build up of polyurethane finish.
Unfortunately, you can't just sand just the polyurethane off of a hardwood floor and not remove wood too... if you try you will burn through to the stain or wood in some spots while totally missing others. So you will end with a blotchy-looking floor. The best method is have the floor prepared for recoating as described above, and then have a very thin coat of polyurethane applied to minimize finish build up.
Polyurethane will not make a wood floor any harder than it already is!
Additional coats of polyurethane will not reduce the dings and dents. Wood, in general, does not scratch but the more hard coating, polyurethane, you put on top of the floor, the greater the bed of material that can be scratched.
Hal Rusche 2nd