Assessing and Addressing Water Damage

Water damage can happen at any time, in any home, and to any type of floor. Water leaks and floods do not discriminate against what types of floors they damage. It makes no difference whether the floor was a one-of-a-kind, custom-run, solid parquet floor, or if it was a low-end DIY snap-together type of wood floor. It also doesn’t make a difference whether the floor itself is somewhat tolerable of some moisture with claims of being “waterproof,” or if it swells with the slightest suggestion that there could be an increase in moisture.

The unfortunate truth is that a water leak or flood will adversely affect any floor, the occupants, and the home it happens in, resulting in costly and time-consuming repairs.

The first step in assessing a water-damaged wood floor is to identify and eliminate the source of moisture. Once the moisture source has been identified and removed, the floor damage should be addressed before further damage occurs. Further damage may not only include damage to the floor, but also to the substrate, or finished living space below the floor.

These are some of the reasons a timely and proper assessment of the water damage is critical:

• Moisture promotes the growth of mold and other organisms, increasing the risk for serious health problems. Studies have shown that mold growth can occur on wood at moisture content levels above 15 percent.

• Corrosion of metal fasteners can occur when moisture content exceeds 18 percent.

• Wood rot and subsequent decay do not occur simply because wood gets wet, but because it has been attacked by decay fungi under specific conditions. Normally, wood must be at or above the fiber saturation point (28-30 percent MC) for a period of time for the fungal spores to thrive and cause it to rot.

Reaching these moisture content levels does not mean mold growth, corrosion, rot or decay, will occur, but does raise the risk for a potential concern.

The following are some items that should be assessed when evaluating a water-damage claim.

Wood Flooring Materials Evaluation

When wood flooring gets wet, it should be assessed to determine the extent of repairs that may be necessary.

• First, identify the type of flooring (species, cut, profile, finishes, etc.) and installation methods in order to properly address the repairs.

• Determine the target moisture content of the flooring as related to the temperature and relative humidity for the geographic area, and for the facility. (Reference the EMC chart.) |

• Consider the time of year that the repairs are to take place and assess the HVAC system’s ability to sustain an adequate environment for the wood flooring.

• Conduct moisture testing.
»Use pinless, dielectric meters to scan the flooring surface and map the damage.
»Check existing, unaffected wood for reference.
»Use insulated pin, hammer probe type meters to achieve readings at multiple depths of flooring and subflooring.
»The target MC should be within 2 percent of expected “in-use” moisture content. (Oftentimes, the drying standards used by restoration companies are higher than the wood flooring requirements. The differential will result in a failed repair.)

• A buckled wood floor requires replacement wherever the buckling has occurred. Once the flooring has buckled, the fasteners or adhesives are no longer effective, and the system will never return to its original state. Once the moisture source has been identified and eliminated, the buckled portion of the flooring will need to be replaced.

Subfloor Materials Evaluation
Water will find its way through any floor covering (even the “waterproof ” stuff) and will potentially adversely affect the substrate. Water damage to the substrate is just as critical to address as the flooring. It is important to understand that water will find its way to places you would never think it could get, and will also follow a path that it deems appropriate based on the scale of the leak or flood. Because of water’s erratic behavior, the areas below and surrounding the wood floor system should be evaluated to determine the extent of damage and ensuing repairs.

Plywood– swelling, distortion and delamination can occur when exposed to high levels of moisture. Moisture tests should be conducted using insulated pin, hammer probe type meters on the surface, on the backing, and within the core of the material in several areas of the damaged material to properly assess the extent of moisture intrusion. Replace when the damage is evident. Ensure replacement material is within acceptable MC ranges and meets all NWFA minimum standards for panel thickness and joist spacing, prior to reinstallation of wood flooring.

Oriented Strand Board (OSB) – swelling can occur with OSB when exposed to water. Swelling in OSB can create a decrease in density and a reduction in within-board strength due to the release of compaction stress created during the pressing process of manufacturing. This will directly affect how existing fasteners hold the wood flooring to the subflooring material. Replace when damage is evident. Ensure replacement material is within acceptable MC ranges and meets all NWFA minimum standards for panel thickness and joist spacing, prior to reinstallation of wood flooring.

Concrete – concrete is a porous material. It typically does not become damaged when exposed to water; however, adhesives, sealers, and other compounds will slow the drying of a wetted concrete slab. Moisture levels must be evaluated and properly addressed prior to installation of new flooring. Concrete substrates should be dried by use of airflow, heat, and dehumidifiers until moisture levels are within the flooring and adhesive manufacturer’s required ranges.

Existing materials below the flooring surface may also create additional mitigation costs and concerns (i.e., asbestos underlayment, lead, radiant heating systems, etc.). A lways be aware of the age and construction methods of the facility, and any potential risks that may affect the overall project. Be sure the end-user is aware of any potential additional costs required to properly address the damage, prior to commencing work.

Unconditioned areas directly below the wood subflooring system or screeds/sleepers, such as basements and crawlspaces, should also be opened to introduce heat and airflow. Any insulation on the underside of the floor joists should also be removed.


• Airflow and heat can be used to speed the natural drying process.

• Dehumidification systems are often used to stabilize the ambient conditions and bring them within the target range.
»Some of the most-effective types of dehumidification systems include desiccant systems and low-grain refrigerant systems.
»Dehumidifiers should be placed on the flooring surface as well as below the flooring surface (when applicable).

• Vacuum extraction systems include placement of large mats/panels that are attached to vacuum/suction systems designed to pull water from the flooring surface.

• Negative and positive air pressure systems force airflow beneath and within the flooring systems in order to decrease the moisture content by direct use of airflow.

If and when water leaks or floods occur, it is important to know with real wood floors, nearly everything is repairable. Many times, minor water damage will dissipate or even completely disappear as the flooring dries out. Major floods will require major repairs. Even the “waterproof ” floors will end up at the landfill with all of the other construction debris when a flood occurs.

Brett Miller is VP of Technical Standards, Training, and Certification at the National Wood Flooring Association in St. Louis. He can be reached at

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