Causes of Hardwood Floor Buckling:

Buckling occurs when the flooring pulls away from the sub-floor, lifting up to several inches in one or more places.

Wood is a hygroscopic material, which means it naturally takes on and gives off water to balance out with its surrounding environment. When wood dries out it shrinks, when it gains moisture it expands.

Water:

Hardwood floors may buckle if they are subjected to excess water. Flooding due to water seepage into the building, an appliance leak, or a plumbing event can result in a buckled wood floor.

Humidity:

High relative humidity in a basement or crawlspace, a new building under construction, a vacant building with the HVAC turned off during the high humidity seasons, or areas that are not well vented and/or properly climate controlled are subject to buckling.

Acclimation:

Most Solid Strip and Plank wood flooring requires acclimation, some proprietary products may not. Acclimation depends on the type of wood flooring product, job site, local environment and any special conditions imposed on the application-there is no set time for this to occur. The moisture content of the wood flooring should be as close to the moisture content of the site's  in-use conditions as possible. In other words, if the average moisture content of a  home will be between 7-9% moisture content, the wood flooring should be within, or as close to that range as possible.

Jobsite conditions that are too wet or too dry during acclimation of the flooring will result in less-than-optimum performance. To determine a base line for proper acclimation, the installer/contractor should  know the expected environmental conditions during both winter (dry season) and summer (wet season) n. A moisture meter is essential to determine when proper acclimation has been accomplished.

Acclimation of Engineered Hardwoods- Always follow individual manufacturer specifications that are available on their respective websites or contained within the cartons of flooring. Pulling planks from cartons days or weeks prior to installation can cause installation problems. Why? Moisture from the environment can actually swell the material ever so slightly (depending on the relative humidity) creating problems with fit of some engineered hardwoods that are milled with precision. Conversely, in extreme dry environments shrinkage may occur. Click type floating floors are very susceptible to these potential problems.

Improper Installation:

For buckling to occur the wood has to gain moisture due to high relative humidity or moisture.  If proper expansion space was NOT provided-  the floor may buckle when it reaches a vertical object, such as a wall, door jamb, or column, or where it's the weakest- usually poorly nailed, rows with no nails, or improperly glued rows. In the right circumstances, wood flooring can buckle without installation related causes.

Preventive measures:

Changes in the humidity levels will affect the flooring; humid areas are more prone to cupping and buckling issues.

Maintain the indoor environment according to the wood flooring manufacturers instructions, usually in the 35-55% and 60-75 degree F range.

If you go on vacation, or spend extended time away from home, try maintaining the recommended temperature and humidity as close to normal in-use conditions as possible. 

If the floor was flooded, contact a company who offers Water Extraction for Wood Floors. New technology allows the technicians to extract the excess moisture with a mat system and/or a water separator,  rather than running dehumidifiers for extended periods of time.