top of page
Search

Why Hardwood Floors Cup, Crown or Buckle–Lift From the Subfloor.


If your hardwood floors are lifting, separating, or showing waves, moisture is almost always the reason. The sooner you identify and address the problem, the better your chances of preventing permanent damage and protecting your investment.


Important Advice for Homeowners

If humidity and moisture are not controlled and addressed immediately, the damage to hardwood floors can quickly become permanent. Prolonged exposure to excess moisture can lead to:

  • Severe cupping or crowning that can’t be sanded out

  • Boards lifting or separating from the subfloor

  • Mold or mildew growth beneath the flooring

  • Costly repairs or even full floor replacement

Taking early action is critical. If you notice your floors starting to warp, buckle, or show gaps, contact a professional right away. Managing humidity and fixing moisture issues early can save time, money, and preserve your floors’ natural beauty.


Hardwood Floor Separation or Lifting

When planks begin to separate or lift from the subfloor, the most common cause is excess moisture.

ree

Common Reasons Hardwood Floors Lift

  • High humidity or poor indoor climate control

  • Wet or unsealed subfloors (wood or concrete)

  • Water leaks or plumbing issues

  • Poor home drainage or crawl space moisture

  • Steam mops or wet cleaning methods

  • Non-breathable rugs that trap moisture


Improper installation can also make things worse — such as using the wrong fasteners or adhesives, or not leaving enough expansion space around walls.


How to Fix Lifted or Separated Floors

  • Find and fix the moisture source.

  • Let the floor and subfloor fully dry.

  • Keep indoor humidity between 30–50% and temperature between 60–80°F.

  • Replace damaged sections and refinish your floors if needed.


Hardwood Floor Cupping

Cupping happens when the edges of each plank rise higher than the center, giving the floor a “dished” appearance. This usually means the bottom of the board has more moisture than the top.

Cupping and early stages of floor separation

Causes of Cupping

  • Moisture from below (crawl spaces, wet slabs)

  • High indoor humidity

  • Over-wet cleaning methods or steam mops

  • Water-based finishes or spills left too long


How to Fix Cupped Floors

  • Eliminate the source of moisture.

  • Allow the floor to dry naturally — this may take several weeks.

  • Avoid sanding until the wood has fully stabilized.

  • Maintain stable humidity to prevent future issues.




Hardwood Floor Crowning

Crowning is the opposite of cupping — the center of the board becomes higher than the edges. It often happens when a previously cupped floor was sanded too early before it fully dried.

ree

Causes of Crowning

  • Sanding before the floor’s moisture level balances

  • High humidity or heat from below the floor

  • Inadequate moisture barriers

  • Poor ventilation


How to Fix Crowning

  • Allow the floor to stabilize and dry.

  • Once dry, sand and refinish if needed.

  • Replace planks that are too thin or damaged.

  • Keep humidity within normal living conditions (30–50%).


Why Wood Reacts to Moisture: Understanding “Anisotropic”

Wood is what’s called an anisotropic material, meaning it reacts differently depending on the direction of its grain.

  • It expands and contracts more across the grain (side-to-side) than it does along the grain (end-to-end).

  • That’s why changes in moisture cause boards to cup, crown, or separate — each part of the board responds differently to humidity.

This natural movement is expected, but when moisture levels swing too much, distortion becomes visible and sometimes permanent.


ree

How to Prevent Hardwood Floor Problems

Consistent indoor climate control is the key to long-lasting hardwood floors.

Pro Tips:

  • Run your HVAC system year-round for steady humidity.

  • Use a dehumidifier during humid months.

  • Avoid steam mops and excess water when cleaning.

  • Choose breathable rugs to let air flow beneath the floor.


Final Thoughts

Wood floors are living materials that respond to their environment. With the right balance of temperature, humidity, and care, they can last for decades.

If your hardwood floors in Charlotte, NC, or surrounding areas are showing signs of cupping, crowning, or buckling, schedule a professional inspection with as soon as possible. Quick action can restore your floors’ beauty and prevent permanent damage.


Best regards,

Jimmy Cameron

Proscout Hardwood Floor Restoration

Mobile: 980.205.3337


 
 
 

Comments

bottom of page