First let’s discuss the most important aspect of a new wood floor sand and finish job, customer expectations. Establishing proper expectations for how the finished floor will look and delivering the look is the key to an acceptable job. We refer to all site – finished floors as “custom finished.” However, this can be separated into two categories--standard finishing and specialty finishing.
For the standard finish, which can include coloring from neutral to light and medium staining, the customer can generally expect the following.
Even coloring: this includes the natural variable coloring of the wood, color variation of the grade of flooring, and natural grain patterns. This excludes color variations associated with the sanding process such as color changes along a wall lines, waves associated with chatter, prominent streaking from heavy sanding grooves, etc.
A smooth surface: the floor should be sanded flat with all mill marks removed and without over wood and under wood. Sander stops, edger digs, and dished grain should be avoided.
The finish itself should be uniform. A consistent gloss level should be present. Puddles, drips, and streaking should not be expected.
The flooring should be sanded only as much as necessary. Over-sanding reduces the life of the flooring and should be avoided.
Of course the corollary is that an occasional mistake of noted exclusions does not cause the floor to fail acceptance. This condition holds as long as the feature is not prominent when viewed from a standing position.
A specialty finished floor can have a completely different set of expectations. The popular distressed and hand scraped floor, for instance, is noted for not being flat. For a specialty finish all parties must discuss the specific look and agree to the expectations before finishing begins. For these custom finishes some customers expect a near perfect floor. We can deliver on this expectation but only with the extra time and precision required. There should also be an understanding this comes with extra cost.
Now that expectations are set, let’s discuss the actual sanding and finishing processes.
Sanding does not begin until the following prep-work has been completed.
Sweep the floor. Embedded grit and debris from other foot traffic must be removed. Vacuuming will likely miss some of this debris.
When sweeping identify and replace or repair problem boards. This includes boards with splits, shake, large broken knots, thin boards and those with bit ends, and other boards with unsound characters. Also, be sure to set all top nails and fasten any loose boards.
SandingThe purpose of the first sanding operation or the rough cut is to remove milling marks and flatten the floor. Today’s precision flooring machinery can produce very uniform flooring that requires less sanding than product from 25+ years ago. Normally a 50 or 60 grit sanding paper is sufficient for this purpose. Also, make the first pass on a 15 to 20 degree angle to the direction of the flooring. If the flooring is rough and these grits do not cut the floor efficiently, sand at an increased angle and/or use a coarser grit for the more aggressive cut. The angle cut prevents the sander from rounding and or highlighting board ends and can prevent telegraphing a sanding wave in the floor. With wide plank this is especially important since straight cutting will likely highlight the ends when stain is applied. After the angle cut it is necessary to straight cut the floor using the same grit as the angle cut.
Edging requires even more care and thought than the drum or belt sander. Edging should also flatten the floor and remove mill marks. A properly set edger will do this with precision as long as the operator does not pressure the machine. Knowledge of the edger’s contact point minimizes sanding irregularities and excessive cross cut scratches. The ultimate goal is to create a scratch pattern that is parallel to the flooring all the way to the wall.
After the rough cuts have been completed, all subsequent sanding is to create a finer scratch pattern associated with the expected finished look. Sanding operations can include fine sanding with the drum/belt and edger machines to 120 grit followed by disc sanding or screening. Too fine sanding can dramatically affect a stain color by lightening the color, particularly the closed grain portions of the wood. The stain contrast between the open grain (darker) and the closed grain (lighter) can be dramatic. Also, for the harder species with few pores and finer graining, too fine grits can affect finish adhesion. The disc sanding can help prevent grain dish out of species with a pronounced softer graining. It can prevent dish out of the softer species in bordered and pattern floors. Proper grit sequence along with proper control of the buffer assures a uniform wall to wall finish and color pattern. For complete details of grit sequences and appropriate cuts associated with different species, attend one of the NWFA Basic Schools held in ST. Louis, MO or an NWFA Intermediate Sanding and Finishing Course.
Application of finish products is next, immediately after the sanding is completed. An overnight delay will require at least a final pass of the buffer since grain raise is likely to occur that affects the staining or make the surface fuzzy. Apply stain/sealers along the direction of the flooring. The typical stains are wipe on, wipe off. Applying too much stain (flooding the flooring excessively) can result in uncured stain oozing from gaps and affecting the curing of the finish top coats. Today’s finishes and the associated VOC changes require that you read and follow the manufacturer’s directions to the letter. The standard comment, “Well I’ve always done it that way,” won’t fix finish problems caused by oozing stain, poly beads, wrinkling, peeling, etc. Remember the darker colors are achieved with a more coarse scratch pattern, not a second application of stain left on the flooring surface. This excess stain will result in peeling and require a complete refinish to bare wood.
Finally the top coat application. Again follow manufacturer’s directions, particularly those associated with coverage rates per gallon. Too thick or too thin can affect gloss levels and drying times. Another critical operation is to evacuate the products evaporating during drying. As soon as the finish has dried to a dust free condition, ventilate to exhaust the saturated air. This assures proper drying/curing and prevents issues associated with soft finish.
Each of the foregoing procedures can also apply to the specialty finish. However, any of the processes can be modified to obtain a special result. These finishes take more time, so to assure the time is in the budget the cost of these operations will be higher to the customer. Typical of a specialty finish is the presentation of a sample panel or to actually finish a floor area for approval of the expected look. In order to duplicate the look for an entire floor, repeat all the processes used on the sample/floor. This means, don’t use hand sanders or other processes, such as spraying the finish, that you wouldn’t use on the entire floor. The result will look different from expected. If you fail in the agreed on look, you will likely either not receive complete payment or have to do the floor over at your expense.
Again set proper customer expectations, then give the customer a product that meets expectations, and everyone is pleased, you get paid and the customer is your advocate and a source of referral and future jobs.