CUPPING - CROWNING - BUCKLING
"Washboard".  Across the width of one piece of the flooring material, the edges are high, the center is lower.  Generally develops gradually.
 

CAUSE:
Moisture imbalance through the thickness is the only cause. The material was manufactured flat and was flat when installed. Job site or occupant provided moisture is greater on the bottom of the piece than on the top. Prove it with your moisture meter. Find the source of moisture and eliminate it. Common moisture sources and their corrections are:
Airborne (Relative Humidity) - dehumidify air space or (lack of during heating season humidify air space); wet basement - ventilate, dehumidify; crawlspace groundcover/vents, add exhaust fan on timer; lot topography - french drain to remove; rain handling provisions - correct to drain away from house; excessive lawn/garden moisture - reduce/waterproof foundation; leaks plumbing, roof, doors - fix; don't hose patio; maintenance; correct capillary through slab - install barrier, french drain, drain tiles. In kitchens, the dishwasher and ice maker are notorious leakers.
Expansion is also the result of site moisture and may have moved the floor tight to vertical surfaces. If so, remove flooring along the wall, or saw cut, to relieve pressure.
 

CURE:
Allow time. Time for the corrections to take effect - to permit the floor to improve on its own. It may become acceptable . After stabilized, sand flat and finish. Cost of corrections should be for owner or builder to cover.

CROWNING, or the center of the piece of flooring (across its width) is high, the edges are lower.

CURE:
After the floor has stabilized following corrections, sand flat and finish. Note: Some slight cup and/or crown can and should be tolerated. It is common in wood floors, especially in wider planks. It is, in many cases, seasonal in its occurrence and can be minimized with lighting and furniture placement, by using beveled products and by other than high gloss finish.
 

BUCKLING, "tented", "ballooning" floors. Pieces of the flooring are no longer in contact with the substrate.

CAUSE:
Generally an extreme moisture problem. See Problem #1 for sources and corrections. Inadequate expansion space, even "net fit" (installer error) prevents normal expansion. On nailed products, insufficient nailing, incorrect nails, incorrect sub floor construction. On glue down product, incorrect mastic, insufficient mastic, wrong trowel used, inadequate mastic transfer, sub floor separation, sub floor contamination.

CURE:
If caught early, spot repair/replacement may be possible. In many cases, however, pull, correct, and relay/replace is more practical.

NORMAL CRACKS-SEPARATION BETWEEN INDIVIDUAL FLOORING PIECES-ABNORMAL CRACKS-LOOSE, NOISY, SQUEAKY FLOOR-UNEVENNESS

CAUSE:
Mother Nature, Dryness.  Should a floor have been exposed to problems 1, 2, &3, then afterwards, "dried out" cracks will develop.  If subjected to extreme moisture, the edges of the wood can crush and subsequent drying and shrinkage can present larger than normal cracks.  Square edge floors show cracks more than beveled.  Most cracks are seasonal, they show in dry months, or the cold season when heating is required, and close during humid periods.

CURE:
Add moisture to the air space during dry periods.  A constant Relative Humidity (RH) of 50% works in concert with the manufacture of wood floors to provide stability in the floor.  Live with normal cracks or add humidity--its the owner's choice.

LOOSE, NOISY, SQUEAKY FLOOR, NOISY, SQUEAKY FLOOR

CAUSE:
Inadequate nailing, flexing weak sub floor system, nailed over particle board type sub floor. Check sub floor thickness and joist direction. Insufficient or incorrect adhesive. Subjected to excess moisture, excessive drying.

CURE:
Add face nails, counter-sink&putty. Strengthen sub floor from below. Inject adhesive or pull-add-relay. Lubricate squeaks with graphite, wax, baby powder. Wedge sub floor up from joists.

UNEVENESS

CAUSE:
Wood joist system - sub floor warped and loose, joists warped or fractured, support pillars settled, perimeter foundation settlement.

Concrete slab system - slab cracked and settled.

CURE:
Correct, strengthen substructure, repair sub floor, splice joists, add joists. Structural, failure is not the wood floor contractors domain usually. Owner needs a general contractor for repairs prior to wood floor corrections.
 

Quality or "Grade"- knots, heavy color variation, out of-square, surface defects.

CAUSE:
Consumer expectations, incorrect sampling, incorrect ordering, mistake by supplier, manufacturer, installer error (should not have installed).

CURE:
Pull and replace offending pieces. Review samples with owner.
 

EXCESSIVE AND EARLY WEAR ON FINISH--SCRATCHES

CURE:
Correct maintenance, especially vacuum, not just broom sweep. Clip dog's nails, felt chair leg glides, appropriate exterior walk-off mats to prevent grit, area rugs especially in front of kitchen sinks. Re-coat if necessary - owner pays.
 

PEELING FINSIH

CAUSE:
Stain not dry. Excessive burnishing. Early coats not dry. Skipped screening between coats. Product incompatibility. Stain not sufficiently wiped leaving heavy pigment on surface (is finish peeling from finish or wood?), improper tack. Surface contaminated such as wax, oil soap maintenance.

COLOR (not right, changed)

CAUSE:
Customer expectation, poor sampling, lighting over the floor and room colorings. In correct maintenance including residue of cleaners, waxes, etc. (i.e., Oil Soap). Wood itself changes color with age ("Patina"). Extreme hot sunlight through South/West facing windows. Color different under rugs or low furniture from lack of exposure. Bleaching is unpredictable - don't oversell expected results.

CURE:
Compare with sample. Explain lighting and colors. Remove residue and correct maintenance procedures. Move rugs and colors will even out in time. Shade large windows.
 

DENTS

CAUSE:
High heels. Dropped heavy objects, metal tips on furniture legs. Unprotected rolling of heavy appliances such as refrigerator or freezer.

CURE:
Remove high heels or maintain proper heel-tip protectors. Provide large felt or rubber protectors under heavy furniture legs. Roll heavy casters over plywood protection only. For individual dents where wood fibers are not broken, cover with a dampened cloth and press with an electric iron to draw fibers up. Last resort sand and finish - owner pays.
 

STAINS / DISCOLORATION

CAUSE:
Water from spills, water from continual source leading to mildew (black) or decay (brown/white) or alkali (white) or bleeding up of adhesive. Urine (dark) from pets, wet diapers. Unprotected metal chair legs. Improper maintenance with water or harsh chemicals. Traffic pattern wear. Excessive harsh sunlight (wood looks starved near South or West facing windows). Light deprivation under area rugs, large low furniture. Be sure to observe if only one piece of flooring is affected, or does the stain continue across adjacent pieces. Oil soap residue.