Flooring Gaps


Got gaps? One of the most common complaints with wood flooring is gapping, or separations between edges of flooring pieces. Board shrinkage is indicative of an indoor humidity imbalance. All the wood in your home will expand or contract as moisture in the air changes. Doors and windows may swell and stick during rainy seasons. In dry, cold weather, cracks and fine lines of separation may appear in cabinets and furniture. Your wood flooring reacts in the same way! It’s a natural characteristic of wood. With properly made and properly installed wood floors, you should expect to have normal gaps during dry months. Seasonal gaps that allow a dime to fit are within the standards and should close back up during seasons of higher humidity!

The ideal humidity level is 30% to 50% and an ideal temperature is 60 to 80 degrees. Maintaining these indoor conditions can even promote a healthier quality of air inside and help sinus sufferers!

The first step to take when you have a gap is to determine what type it is. Is the gap normal, job-related, material-related, or something else?

Normal Gap

Normal gaps have various interpretations, depending on width of the strips, boards used, the size of the room, and the severity and duration of low outdoor temperatures (and hence the intensity of heating).

Generally, gaps between strips are normal in strips 2¼" wide or less if they close up in seasons of higher humidity. Normal gaps may vary in width from hairline gaps to the thickness of stationary, to more significant gaps the thickness of a quarter or greater. Greater gaps are expected in areas with an extended dry heating season and mild summers with little need for air conditioning.

Again, if the floor expands during non-heating seasons, it should be considered normal.

Job-Related Gap

Large gaps in wood floors that do not close up in summer months can have either job-related or manufacturing defects as the cause. A job site inspection should determine the cause. Excessive moisture, incorrect nail spacing, and more can cause abnormal gapping.

Material-Related Gap

If wood is manufactured improperly, abnormal gaps can occur. This usually occurs because the lumber is not adequately dried before the flooring is milled.

Other Causes

  • System movement: when outside walls settle or a house’s center beam moves
  • Over-drying: around heating ducts and vents
  • Improper subfloor: If the subfloor doesn’t hold nails, gaps can occur


Replacing a floor to get rid of gaps is usually unnecessary.

For normal gaps, no repairs are practical. These spaces are necessary for humid season expansion and, if filled, can cause so much stress the floor may buckle or the edges may be crushed. Any filler will be pushed out as the wood expands with moisture.

For abnormal gaps, a professional contractor can properly repair floors. Consult a professional! The time to initiate repair is midway between seasonal extremes. For much of the U.S., this means near the months of April or October.

First the flooring should be assessed for movement between strips. Strips may require face nailing near the groove edge to eliminate movement. Next, thoroughly clean the gaps. Old filler and trash should be scrap and vacuumed away. Then filler is applied in the gap. Coloring, screening and re-coating may follow if there is a surface finish.

When properly repaired, gaps are generally lost sight of. Filler should remain in the gaps after repeated seasonal changes. For more information and assistance, please contact our Tech and Install department at 800-366-4204.



  1. We have cherry on the floor, the whole length of the floor, a straight line, there’s a gap thats at least 1/4 inch wide. It closes some in the summer months but looks bad right now. What can we do?

  2. With proper installation methods the gaps in wooden flooring can be avoided. Now various types of treated flooring boards are available which can resist swelling and contractions.

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