Hardwood Floor Cupping and Buckling-Crawl Space Moisture

Hardwood Floor Cupping and Buckling-Crawl Space Moisture

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Before purchasing a Hardwood Floor:

The following article explains how moisture develops in a vented crawl space, what moisture does to hardwood flooring, who’s responsible for moisture damaged hardwood flooring and how to prevent crawl space moisture problems before installing your new wood floor.

The National Wood Flooring Association (NWFA) and wood floor manufacturers recommend 6-mil polyethylene sheeting over exposed earth in the crawl space and vents must be open at all times. Also, vents must equal at least 1.5% of the total square footage of the crawl space.

The fact is industry standards may be inducing failures in areas with hot, humid conditions by requiring a crawl space vents.

When hardwood flooring fails because of moisture the manufacturer or distributor may commission a certified flooring inspector to evaluate the cause of the claim. Moisture related claims are not warranted because moisture from any source is beyond the control of the manufacturer, and is not related to the manufacturing process. Responsibility for the failure is placed on the homeowner or the installer.

The homeowner did everything they were told to do so they don’t want to accept responsibility. The installer won’t take responsibility because conditions were good at the time of installation. In the end, the homeowner is dissatisfied with their purchase and wants the flooring replaced, they may even threaten legal action. The flooring installer or retailer has an unhappy customer because they recommended, and followed industry standards that created conditions beyond their control. If the flooring is replaced, the replacement floor may cup or buckle again if the cause of failure is not addressed.

How to Prevent Crawl Space Moisture:

The experts Advancedenergy.org determined that allowing hot, humid air into a vented crawl space will increase moisture— the exact opposite of the flooring industries requirement. Their studies indicate that sealing or closing a crawl space not only creates a healthier environment, it reduces mold, insect and rodent infestation, and conserves energy cost by reducing utility costs. The bonus is protecting your wood floors from cupping and buckling.

Closing a vented crawl space is not too difficult or expensive if you’re a fairly handy, others may consider hiring a professional. A do-it-yourselfer should pay careful attention to the advice of Advanced Energy if you have a furnace or water heater in the crawl space.

Why Wood Floors Cup:

Hardwood flooring cups (edges rise above the center of the board) when there is a moisture imbalance from the top to the bottom of the boards. Wood floors cup when exposed to moisture from below.

Why Wood Floors Buckle:

Buckling occurs when the flooring separates or lifts from the sub-floor. For buckling to occur the floor has to gain moisture, expand and meet a location(s) that prevents it from expanding; this may be a wall, column, doorway or any other vertical object that prevents the floor from expanding.

Moisture in Vented Crawl Space:

Crawl space ventilation was developed to maintain circulation of fresh outdoor air into the crawl space; to remove damp air that settles in the crawl space.

Understanding the Problem of vented crawl spaces:

The experts found that problems begin when warm air enters a house; it rises to the upper regions, similar to air moving up a chimney. This phenomenon is called the “stack effect”, it causes the home to suck air up from the crawl space into the living areas of the house. In addition to moisture, contaminants that develop in the crawl space such as mold spores, and fecal matter from dust mites and insects enter the house by way of stack effect.

When hot humid air enters a crawl space, it instantly cools, increasing the relative humidity in the crawl space. When the relative humidity reaches 100%, moisture is released into the crawl space leading to condensation on colder surfaces such as wood and metal pipes. This dampness leads to mold, rot and insect infestation and rises into the house along with mold spores and insect fecal matter.

As crawl space moisture increases, mold develops on the floor joists and subfloors, and water begins dripping from insulation. The crawl space has now become the perfect home for insects and rodents.

In hot, humid weather wood subflooring and floor joists can measure 25-30% moisture content in a typical vented crawl space. In the same environment, the wood flooring’s moisture will measure 7-10% in the house or building. Problems arise when the moisture difference between the sub-floor and wood flooring becomes too great and the floor begins to cup. If the wood floor reaches its limit of expansion, it may buckle.

During the winter, vented crawl spaces allow cold air into the house (stack effect). The cold air cools your hot water pipes and hot air vents. Your heating bill increases, and the house is uncomfortable and drafty. A sealed or closed crawl space prevents cold winter air from filling your crawl space and the interior of your house.

Signs of a Wet, Moist Crawl Space:

  • Musty odor
  • Water stains on the foundation walls.
  • White crystals(efflorescence) or powdery fluffy, fuzzy deposits on the block or concrete.
  • Rusty metal
  • Black discoloration on wood floor joists or bottom of subfloor
  • Dripping, dirty fiberglass insulation.
  • Water dripping from metal objects, insulation or plastic
  • Standing water
  • Cold or moist sand or soil

    More to come….,
    Linda Lockwood
    Statewide Floor Covering Inspection Service


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