Buckling And Cupping On Flooring

With hardwood flooring being the fastest growing segment in the flooring industry, problems also increase in number. One of these problems is the floor lifting from the sub-floor surface and is commonly called buckling. Usually problems with buckling or cupping in a wood floor are caused by excessive humidity inside or under your house. It's possible that a non-permeable house wrap was used behind your new siding, which is increasing the humidity level in your home; or that the siding covered up existing foundation vents under your home. In either case, you should monitor the humidity level inside and under your home using a humidity gauge (hygrometer) to make sure both areas are under 60% relative humidity. Solid wood flooring moves constantly as the humidity level changes – expanding when the humidity is high and contracting when the humidity is low. This problem is particularly pronounced during a hot, humid summer or cold, dry winter.

What's the Buckling?

Buckling is defined as lifting off the sub-floor surface and can be found on concrete sub floors and wood sub-floors. All flooring can buckle even carpet and stone floors, given the needed conditions to expand in size. Wood, by its nature, swells with the increase of moisture content and shrinks with the loss of moisture content.

Buckling is the result of wood floors swelling and having no place to go but up and off the sub-floor. The condition needed to result in buckling is the addition of moisture or water to the flooring. Flooding is the obvious, with increase in moisture the most difficult to detect.

Flooding from broken pipes, appliances or water overflowing the bathtub or sinks are common sources of water flooding hardwood flooring. These conditions are easily detected because they are visible and easily seen. Flooded floors may not buckle if the water is removed soon after the event and dried using fans and de-humidifiers. But allowing water to remain in the wood flooring will most likely result in the floor swelling and buckling.

The addition of moisture, from environmental vapor, is difficult to identify and may require a certified professional or inspector to determine. This condition stems from installing dry wood in a damp environment or the environment changing after the installation.

In southern states we see this condition after hurricanes and the resulting power failures. The interior of the home increases in relative humidity and wood moisture content causing the boards to swell and lift off the sub-floor. The buckling condition allows movement of the flooring boards causing a squeak sound and sometimes a squeak noise caused by two boards rubbing together.

Buckling may not be a repairable condition and may require removal and re-installation.

Reasons for Flooring Buckling or Cupping

· If the humidity level inside or under the house is much higher than the wood flooring was acclimatized to when it was installed, it can cause the boards to expand and buckle.

· If the humidity level inside or under the house is much lower than the wood flooring was acclimatized to when it was installed, the flooring may shrink and leave gaps between the boards.

· If the humidity level is much higher or lower inside your house compared to under it, it can lead to the boards cupping.

· If the flooring cups down (the center of the width of each floor board on top is higher than the edges), the humidity inside your house is substantially higher than the humidity in the crawlspace or basement under it.

· If the flooring cups up (in a "U" shape on top), the humidity in the crawlspace or basement is much higher than that inside your house.

How to Reduce Humidity Inside a House

· Run a properly sized air conditioner during hot, humid weather.

· Use bathroom vent fans (vented to the outside) during and for 10-15 minutes after showering or bathing.

· Run a kitchen stove vent fan (vented to the outside) when cooking.

· Make sure the clothes dryer vent is unobstructed and vents outside your house.

· Consider installing a dehumidifier if the above suggestions are not enough to lower the humidity level under 60%.

How to Reduce Humidity Under a House

· Make sure there isn't any standing water in the crawlspace or basement under your house caused by plumbing leaks or drainage problems.

· Be sure the ground slopes away from your house, and rainwater is diverted away from the foundation.

· Seal the walls and floor of your basement with a waterproof sealer, or cover the ground in the crawlspace with thick (6-mil or more) plastic sheeting.

· Make sure there is adequate ventilation in the crawlspace under your house (1 square-foot of vent space per 150 square feet of crawlspace).

· If problems with high humidity in the crawlspace or basement under your house persist, consider closing up all vents and installing a dehumidifier under the house or conditioning the space under the house.