Sanding & Refinishing
- Sanding and Preparation
- Types of Polyurethane - Oil Modified vs. Waterborne
- Finishing Processes
- Maintenance Recoats / Topcoating
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Refinishing ProceduresThe process of hardwood floor sanding and refinishing may present a certain level of uncertainty for anyone who has not had first-hand experience with it.
There are many steps involved in sanding and preparing newly installed or pre-existing hardwood floors. Moreover, the refinishing process itself will present several possible options to achieve the results desired for your home's specific interior design concept. The following is a walkthrough provided by Inter-County Floor Sanding as to the various steps necessary to complete a hardwood floor service project.
Sanding and PreparationOur well-trained craftsmen begin by determining the proper grit sandpaper required and a number of sanding passes necessary for each specific work site. Based on experience, the mechanics will recognize the grit needed to remove any old finish, scratches and/or embedded dirt within the wood floor. Yet still not allowing too much wood to be removed with each pass. The floor may need two to four sanding passes depending on the age and type of finish, and the condition and species of wood being refinished. 
Newly installed unfinished hardwood floors will need to be sanded as well, due to slight milling imperfections and minor board edge unevenness.
We utilize the flooring sandpaper grit grades of 12, 16, 20, 30, 36, 40, 60, 80, 100, and 120. The main areas of the floor are sanded with a large professional 8" drum/belt sander, while the perimeter is completed with a circular edge sander. A hand scraper is used to remove the old finish from corners, bullnosing on steps or ledges and generally any small area our sanders can not reach.
After the hardwood is completely sanded, a fine-grit silicon carbide sanding screen is then passed over the floor with an upright buffing/polishing machine. This extra step is taken to ensure the wood has been sufficiently smoothed down and that the grain has been evened out.
Of course, all of our equipment has vacuum ports built directly into their housings. They connect with crush-resistant 2" hoses to our Dust Containment Vacuum System, producing a 99% dustless environment.
The floor is then vacuumed and tacked (passed over with a dampened towel) to remove any dust, prior to stain or finishing polyurethane being applied.
Between polyurethane coating layers the hardwood floor is abraded with a sanding screen as well. The first coat of polyurethane commonly absorbs into the wood and raises the grain. This will give the dried coating a slightly irregular and rough feeling - which is perfectly normal. The dried polyurethane simply requires a 'screening', so the floor will be made smooth prior to cleaning and recoating again.
Types of PolyurethaneWe utilize the two most common types of hardwood floor polyurethane coatings. These are an Oil Modified polyurethane and a Waterborne polyurethane.
Both of these finishes are available in Gloss, Semi-gloss or Satin sheens. The image below displays general representations of what your floor may look like when polyurethane is applied to your hardwood floor.
Oil modified polyurethane:
This a petroleum/oil-based finish containing plasticizers and various synthetic resins. This finish is solvent-based and there is normally an odor associated with it. It will normally dry to the touch (walking in socks) in about eight hours. However, depending on worksite conditions, temperature, and humidity (all variables on Long Island) - drying may vary from six to twelve hours. Curing time for recoating, replacement of furniture, or allowing other remodeling work traffic will require skipping a day before such activities may resume. The oil-modified polyurethane itself generally has a transparent amber appearance and has a 
viscosity similar to new motor oil. When applied to an unstained bare wood the floor it will continue to retain this golden color. It requires a minimum of two coats to protect a floor, but three is the industry standard for sustained durability.
Waterborne polyurethane:
This a water-based finish containing plasticizers and various synthetic resins. It has a milder odor in comparison to oil-modified finishes. This product normally dries to the touch (walking in socks) in about two hours. However, depending on worksite conditions, temperature, and humidity - drying may vary from one to four hours. Curing time for replacement of furniture, or allowing other remodeling work traffic will often require waiting until the following day before such activities may resume. The waterbased polyurethane itself generally has a milky white appearance (but dries clear) and has a viscosity similar to heavy cream. When applied to an unstained bare wood the floor it will appear to have a light beige/blonde color. It requires a minimum of three coats to protect a floor, but four is highly recommended for sustained durability.
Finishing ProcessesAfter the floor sanding process has been completed, there are three basic finishing procedures available. For reference purposes, they are termed “Natural”,and “Stain”processes.
Natural/Clear Process:
In this procedure, polyurethane is applied directly to the bare wood surface. No wood stain or any type of coloring is applied to the floor prior. This clear coat process will render the floor a light amber or golden honey color [as shown above]. Factors such as the hardwood species, age, and grading, will often affect the final color achieved on the floor.
Polyurethane is applied to the edges of the rooms by a hand brush, whereas a lambswool pad (applicator) mounted on a 16" wooden block is used to apply finish to the center of the floor.
Stain Process:
With this process, a wood stain is applied to the floor, and hand wiped, prior to any protective polyurethane coatings. This stain is for cosmetic purposes only and will have no effect on the protection of the floor. After the stain is allowed to cure, polyurethane coatings are applied over the dried stain as in the natural process listed above.
We commonly use Minwax® brand Wood Finish™ Stain and DuraSeal Quick Coat wood stains. If you prefer to have another manufacture's stain applied, please let us know and we will gladly use it.
Factors such as the hardwood species, age, and grading, will often affect the final color achieved on the floor. The chart below will provide a basic reference point as to how stain colors will appear. Electronic screens on phones and computers will not always be accurate. Also, hardwood floors have a variety of floorboard shades. Each board will take the stain slightly differently than the board next to it. If you look at your floor now you will see multiple colors throughout all the various boards.
**Pickled Oak, Weathered Oak, White and Gray stains require an aliphatic non-yellowing urethane as opposed to a standard waterbased polyurethane.
Maintenance Recoats / Topcoating
Several years after a hardwood floor is completely sanded and finished a maintenance coat will be needed to sustain the floor's performance and cosmetic appeal. This recoating procedure, commonly called a 'topcoat', will return a hardwood floor to its newly refinished condition - provided it was performed within the ample period of time required.
A 'screening' of the original polyurethane coat, with a silicon carbide sanding screen on an upright floor buffing machine [animated right], will remove any light scuffs and surface dirt. The screening process does not remove much of the existing coatings, nor does it expose the bare wood as in the full sanding procedure. It simply creates microscopic scratches in the surface of the existing polyurethane coat. These abrasion scratches enable the new coating to properly adhere to the older one.
Please note that If your hardwood floor has ever been cleaned with an unapproved hardwood polyurethane floor cleaner or wax had ever been applied (liquid or paste) to your wood floor this topcoat procedure generally CAN NOT be performed. Polyurethane does not adhere to certain chemicals or cleaners that leave a film or wax on the floor. Unfortunately, Inter-County Floor Sanding cannot 100% guarantee that a topcoat will have absolute cohesion with an existing floor finish due to the fact that we have zero control over what may or may not be on an existing finished floor.
