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F A Qs about Wood Floors

PROBLEMS, CAUSES and CURES (FIRST AIDE SUGGESTIONS of common wood floor problems and concerns)


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

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.

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.

While moisture imbalance might be the cause (by excessive moisture introduced on the finish side of the floor; i.e. water used in maintenance, plumbing leaks overhead sprinkler system), it is more likely that the floor was cupped (problem #I) and sanded flat thus removing the outer edges, the sanding having been done at the wrong time, i.e., before corrections were made and before the floor flattened on its own.

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.

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.

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



Mother Nature. Dryness. As moisture caused some earlier problems 1, the loss of moisture results in the most frequent reason for shrinkage of individual pieces and cracks. 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 (a vegetable made up of cells), can crush, and subsequent drying and shrinkage can present larger than normal cracks. Square edge (un-beveled) floors show cracks more than beveled. White, light, pastel finished show cracks more than darker wood-tone finished floors. Most cracks are seasonal - they show in dry months, or the cold season when heating is required, and close during humid periods. This type of separation and closing is considered rm 1. In solid 2 1/4" wide strip oak floors, dry time cracks may be the width of a dimes' thickness (1/32"). Wider boards will have wider cracks (and the reverse is true).

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 owners' choice. Easy ways - boil a pan of water on the stove, turn off bathroom exhaust fan, open dishwasher after rinse cycle, a pan of water in furnace fan compartment, hang laundry to dry in basement. Better yet, install humidifier to furnace controlled by a humidistat set at 50% RH. In dry and warm climates, add moisture (pan or humidifier) and run furnace "fan only".

ABNORMAL CRACKS: Abnormal cracks - larger than normal, cluster or localized, end separation, not uniform and not general throughout, do not close up during humid months.

Edge crush from prior exposure to extreme moisture, especially solid, flat grain flooring (and may be general throughout). If surface coated (such as polyurethane), edges of some adjacent pieces may be literally "glued" together, or panelized, and shrinkage cracks multiplied at the weakest points. (See note that follows) "Hot Spots" in the undersurface such as poorly insulated heating ducts, hot water plumbing lines, radiant heating system (if so, should be laminated products only), the new "Instant Hot Water" feature, register openings, heat from refrigerator motor, check nail spacing with stud finder. With adhesive applied floors, early foot traffic, incorrect adhesive, amount transferred or used (most noticed in traffic pattern). 3/4" thick solid parquet with no return control (cork) in expansion space, generally indicated by center of the field is tight, with gaps around the walls. Note if there is a pattern to the cracks, such as 4' X 4' or 4' X 8' indicating sub floor change or weakness. Glued over sheet vinyl may show 6' cracks from shrinkage or loose vinyl. Does the pattern of cracks convey a relationship with foundation or slab cracks and/or settlement. Check nail spacing on solid products take wood moisture content reading and if it is within normal range for your market and the wood is undersize, drying was improper prior to manufacture. If wood MC is normal and wood is "on size" or over, the wood was wet prior to installation.

In addition to obvious corrections suggested under it cause" (i.e., add insulation between heat ducts and sub floor for "hot spots", pull, add adhesive, relay, adjust 3/4 parquet, add expansion joint control, add cross bracing under weak sub floor), attempt to elevate the relative humidity in the air space and after sufficient time has passed to confirm that the problem has stabilized, fill the cracks with the appropriate color-matched fill. Re-coat if necessary. Last resort, pull and replace - note however, that if corrections are not made, chances are that replacement will develop the same problem. Note: When a floor shows "panelizing" and a surface coat has been used, you might choose to sand then finish with seal and wax, or if surface finish is required, use a sealer first rather than the stronger finish directly on the new floor.


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.

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.

UNEVENNESS-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.

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, traffic pattern. Finish Peeling - bubbles, blister - ROUGHNESS

CAUSE: Improper maintenance, grit, water, strong soaps, dog toenails, chair legs.

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.

Finish Peeling - bubbles, blister

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.

CURE: If de-lamination from wood surface, sand and refinish. If surface only, screen and re-coat.

Pet Stains CAUSE- (We all know the cause !)
CURE: For the most part minor pet stains will lessen or get lighter with sanding. Repeated stains (the darker the deeper) will not sand out. Several consideration must be given. 1 - Will the floors be refinished ? If so, a light or medium colored stain can be use to help "cover or lessen" the stains. Sometimes a "painted" design on the floor will cover the stains, or the use of area carpets over those stained areas. 2 - Removal and repair will give BEST results, if time, and budget allowances are made.


CAUSE: Moisture from maintenance, spills, constant source, condensation causing surface grain raise. Poor sanding, edging, scraping. Contamination in finish during dry time.

CURE: Correct moisture source. Lightly sand or screen. Re-coat.

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 - Yes, wood dents.

CAUSE: High heels. Pet nails, 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. Keep pet nails clipped. 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.


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.

CURE: Correct water source, let dry. Minimize sunlight. Relocate area rugs. Correct maintenance procedures and products. Dark stains, lightly abrade surface with fine sandpaper, feather out area, dampen cloth with 50/50 household bleach & water and lay on stain for 30 minutes, remove, let dry, re-color if necessary. Waxed floors, clean with renovator or paint thinner (combustible) and re-wax. Whiteness/cloudy surface finish, clean and buff. If all fails, screen and coat, sand and refinish, replace severe boards.

First Aid for Surface Finishes


  • Cigarette burns:
    Most common burns can be treated with touch up kit (rub with steel wool /sandpaper, stain as needed, touchup finish)

    If burn is deeper, boards/pieces may have to be replaced


  • Chewing gum, crayons, wax

    A plastic bag filled with ice on top of deposit until brittle enough to crumble off. Clean area with cleaners made for urethane finishes


  • Greasy spots, Food

    Cleaners made for urethane finishes (cleaning kit from your wood floor retailer)


  • Scratches

    Repair with touch-up kit from your wood floor retailer, "Endust" on a soft cloth, wipe in direction of scratch will help bring back the color. 



    CAUSE:Termites-Identified by eating corridors beneath surface which when weakened, the fragile surface sags. The bugs are white or cream colored. Subterranean type build sand tubes. Powder post Beetles identified by 1/ 16" diameter perfect circle hole in surface of floor. Active infestation will show clean bright wood in holes with fine talcum powder like dust piles around the holes. Inactive holes are darkened, even show stain or finish on walls of the hole. When in doubt, collect sample bugs, consult exterminator, entomologist, or extension service, etc.

    Structure must first be rid of active termites by professional exterminator. Repair structural damage. Pull and replace damaged floorboards, sand and refinish. Heavy infestation of powder post beetle, handle as above. When powder post is occasional, few boards especially in new floors, treat individual openings immediately with insecticide (from hardware or garden shop) injected by syringe into holes, or aerosol insect spray through a straw. Usually will not disturb finish. Have owner watch for new evidence (dust piles) and treat again. After 2-3 months holes may be filled. Termites will not be associated with the flooring and costs will be the responsibility of the owner. Powder post may be in new flooring materials. Immediately on first report notify your floor supplier. Prompt action by all will minimize costs involved. Check all surroundings for infected wood molding, furniture (especially bamboo and antiques). If old infestation is in other materials the owner must stand the costs involved in floor repairs.

    Wood Damage by Termites:
    Wood damaged by subterranean termites is often not noticed because the exterior surface usually must be removed to see the damage. However, galleries can be detected by tapping the wood every few inches with the handle of a screwdriver. Damaged wood sounds hollow, and the screwdriver may even break through into the galleries. Subterranean termite feeding follows the grain of the wood and only the soft springwood is attacked. Unlike dry wood termites or other wood boring insects, subterranean termites do not push wood particles or pellets (fecal material) to the outside, but rather use it in the construction of their tunnels. This debris, along with sand and soil particles, is used as a form of plaster.

    The best control of subterranean termites is prevention. The best time to provide protection against termites is during the planning and construction of a building. Prevention should include: 1-Removal of all stumps, roots, wood, and similar materials from the building site before construction is begun. 2 -Removal of all form boards and grade stakes used in construction. 3-There should be no contact between the building woodwork and the soil or fill. Exterior woodwork should be located a minimum of 6 inches above ground and beams in crawl spaces at least 18 inches above ground to provide ample space to make future inspections. 4- Ventilation openings in foundations should be designed to prevent dead air pockets and of sufficient size to assure frequent changes of air - at least 2 sq. ft. to 25 running feet of outside foundation wall. This helps keep the ground dry and unfavorable for termites. 5- Thorough annual inspections should be conducted to discover evidence of termite activity such as shelter tubes on foundation surfaces, discarded wings or adult termites. 6- Any wood that contacts the soil, such as fence posts, poles and general foundation structures, should be commercially pressure treated.

    Control subterranean termites by preventing the termite colony in the soil from entering the structure. It is impossible to build structures so termites cannot cause damage. Therefore, a thorough pre-construction treatment should be applied to protect the structure for 5-20 years. Houses treated prior to 1988 with chlorinated hydrocarbons, should be protected from subterranean termites for 30-40 years. Several insecticides have proven satisfactory for making effective barriers when properly applied.

    After the footings are poured and the foundation walls and/or piers have been constructed, apply the insecticide to a trench in the soil about 6-12 inches wide and 4-6 inches deep adjacent to the foundation. The insecticide must be applied to both the inside and outside of the foundation and also around piers, chimney bases, pipes, conduits and any other structures in contact with the soil. The trench should be as deep as the top of the footing. The insecticide should be mixed with water as recommended on the pesticide label and applied at the rate of 2 gallons per 5 linear feet of trench. The insecticide should be mixed with the soil as it is being replaced.


    SLABS The most common type of construction in Florida is concrete slab resting on the soil. Often the slabs crack or shrink away from the foundation wall allowing termites to infest the wood above. The soil underneath and around the concrete slab should be treated with insecticide before the concrete slab is poured. The chemical should be applied after all the subslab fill and reinforcement rods are in place. Apply diluted spray to the fill at the rate of 1 gal. per 10 sq. ft. Along both sides of foundation walls and interior foundation walls and plumbing (critical areas), apply diluted insecticide at the rate of 2 gal. per 5 linear feet. Treat all hollow masonry units of foundations with I gal. of diluted spray per 5 linear feet. Apply the insecticide to reach the footing.

    Crawl Space Treatment Dig narrow trenches along both the inside and outside of foundation walls and around piers and chimney bases, and apply diluted spray as described above. Also be sure to trench and treat around sewer pipes, conduits and all other structural members in contact with the soil. Apply the insecticide to the trenches. The insecticide must be applied to both the inside and outside of the foundation and also around piers, chimney bases, pipes, conduits and any other structures in contact with the soil. The trench should be as deep as the top of the footing. Mix the insecticide with water as recommended on the pesticide label. Apply the diluted spray at the rate of 2 gal. per 5 linear feet of trench. Mix the insecticide with the soil as it is being replaced.

    Concrete Slab Construction
    It is possible to trench around the outside of a slab after it has been poured, as described above, but this alone usually will not give satisfactory control because the termite colony may be entering the structure from the soil under the slab. Homeowners are not equipped to treat under slabs after the slab foundation is completed. A professional pest control operator usually is needed to do subslab chemical injections. Most subterranean termites feed along the grain of the wood, eating the spring wood and leaving the summer wood. The Formosan termite feeds on both and forms a hollow. In Hawaii, where unprotected homes were built over large colonies, records show that the Formosan subterranean termite caused major structural damage in 6 months and almost complete destruction in 2 years (Tamashiro 1984). Moisture Requirements The Formosan termite, like all subterranean termites, uses the soil for a source of moisture. However, Formosan termite colonies can obtain moisture from plumbing or roofing leaks.

    Inspect for evidence of termite activity near any plumbing that goes through the slab. Look for tubes around baseboards. Tap baseboards around walls. Check for wood which is in contact with the soil.

    THE VACANT HOUSE - "Greenhouse Effect"

    CAUSE: Security -conscious vacationers, a homebuilder's unsold inventory, whenever a wood floor is deprived of an air flow in the environment, it can and will misbehave. Sunlight through windows generates heat, lowers humidity, moisture vapor enters to balance, nights cool off, humidity builds and wood floors cup. Thermostats set at 60 degrees and outside, winter howls, heating system runs constantly with no moisture added, and floors shrink.

    CURE: Avoid problems by leaving windows "ajar", have neighbor air the house out occasionally. Treat floors as discussed under cupped, tented, or shrinkage cracks and only after environment returns to normal. Owner to pay.
    The above commonly ask questions will help you and your wood floor contractor resolve some of the everyday concerns about wood floors. By no means is this a sure method or procedure. If in doubt, get a second opinion.



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