Home » Hardwood Floor Buckling and Cupping in Summer – What to do

Hardwood Floor Buckling and Cupping in Summer – What to do

Hardwood floors impart a distinctive character and natural color to a home. The timeless feature adds value to your property and therefore requires proper care and maintenance.

Hardwood floors are expensive to buy and install and are susceptible to environmental factors such as and humidity and temperatures.

Moisture or water is the greatest enemy of a wood floor, which is why it buckles more during a hot summer or dry winter.

When summer arrives, temperatures tend to rise and so do humidity levels. The sunlight also becomes more intense.

During this period, a number of issues can arise and any home owner with a hardwood floor need to be on the lookout.

Besides wood warping, buckling or cupping, the intense UV radiation from the sun can also lead to discoloration if allowed to directly strike your wood.

Understanding Cupping, Warping and Buckling

Cupping happens when wood absorbs excess moisture causing it to swell and crush the boards together as they deform at the edges and forms a cup- like shape.

The edges of a board becomes higher than its center.

Warping happens when wood dries unevenly in the process of losing moisture. This makes curve to a bow, crook, cup, or twist.

Buckling occurs when wood flooring boards pulls up from the subfloor. The boards are moved up several centimeters or inches in one or several places.

Reasons for hardwood buckling during summer

According to Claudette Reichel, LSU AgCenter housing specialist and director of LaHouse Home and Landscape Resource Center, raised floor homes are the most affected during summer with wood cupping and moisture problems.

She noted that raised floors get wet in summer due to a combination of cool air conditioning and impermeable floor finishes.

She further explained that moisture moves from warmer to cooler areas and from wetter to dryer areas. That means that, if you air condition your home during hot, humid weather, water vapor moves from outside to inside.

Moisture will also condense on the subfloor when the subfloors become cooler than the dew point outside.

The moisture will therefore try to move inside and cupping will start taking place when the moisture cannot escape through the floor boards due to impermeable sealants such as polyurethane.

“The wet subfloor wets the bottom of wood flooring, which causes the bottom of the planks to swell, causing cupping in summer,” said Mrs. Reichel.

Reichel’s Recommendations on how to reduce humidity inside a house

  • Keep your house warmer in summer by setting the air conditioner above the outside dew point.
  • If you want to keep it a little cooler, ensure that all your wood floorings have moisture permeability.
  • Do not allow any water to flow under the house or pool on the plastic sheeting as that can worsen the problem in humid areas.
  • Invest in subfloor airtight treatments and insulating vapor barriers across all joists, seams and edges by using fire-rated, foil-faced rigid foam boards and closed-cell spray foam insulation to create an airtight system.
  • Your pest control contract terms should include subfloor foam insulation systems in the event of termite activity around your home.

However, Mrs. Reichel cautions against insulating while the subfloor and flooring are wet.

She suggest best time is during end of winter when the floors are dry outside and when the home has been properly heated in the cold weather.

If summer causes a damaging effect on your wood floor, you will have to call a professional at the end of the season who may recommend the next move based on the damage.

However, Mrs. Reichel noted that cupped wood flooring should not be sanded down flat until it is completely dry.

“Cupped planks will flatten as they dry unless they have splits, so wait for them to stabilize,” she said. 

“The time to refinish wood flooring is after it’s flattened as much as it will. If you sand off the cupped edges before it flattens, you could end up with a ‘scalloped’ floor in winter after it dries.”

How to reduce Humidity under a House

Humidity buildup under a house is one of the main reason for a wood floor's cupping and buckling.

Here is how to ensure that doesn't happen again:

  • Ensure that no water is standing in the basement or crawl space under your house. Fix any leaks and drainage issues that are causing it.
  • Divert rain water away from your house by landscaping or digging a trench.
  • Invest waterproof sealants such as plastic sheeting and insulators in your subfloors.
  • Create ventilations in the crawlspace under the house.
  • Install air conditioning or a dehumidifier under the house.

Air conditioners and dehumidifiers are the main appliances for regulating indoor moisture levels. Running them at the recommended levels will balance the indoor temperature and relative humidity optimum for hardwood floors.

The type of hardwood flooring in your home can also help minimize the adverse effects of moisture.

Engineered wood is more stable when reacting to temperature and moisture levels. It is the best type to install in areas with high extreme weather conditions.

Additionally, wood must be properly acclimated to the environment before it is installed.

According to the National Wood Flooring Association (NWFA), wood floor acclimation is “the process of adjusting (conditioning) the moisture content of wood flooring to the environment in which it is expected to perform”.

Wood flooring will always perform best in ideal range of temperature and relative humidity.

The environment should be controlled to remains within a relative humidity range of 30-50%. The temperature should also be within a range of 60-80 degrees Fahrenheit.

Other than moisture issues, during summer your wood floor can also discolor. Too much exposure to UV radiations from the sun can lighten your hardwood floors.

Therefore, keep the blinds closed or curtains to prevent the sun from directly striking your wood.

The Bottom Line

Regular cleaning that involves daily dusting or weekly vacuuming and using a hardwood floor cleaner once per month is the trick to keeping your wood sparkling clean all the time.

Deal with spills immediately and protect the floor from scratches using area rugs at the entrances and furniture pads on your furniture to enjoy the timelessness feature of a hardwood floor.

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