If you’ve ever walked across a hardwood sports court or dance floor, you might have noticed small gaps between the wooden boards. While these gaps might seem concerning at first glance, they’re actually an essential feature of proper hardwood floor installation. Let’s explore why these gaps exist and when they might indicate a problem, based on research from Dr. Paul W. Elliott, PE, President of ASET Services.

Read ASET Services white paper: GEN-007: Gaps in Hardwood Sport/Dance Floors

The Science Behind the Gaps

Wood is a hydroscopic material, meaning it naturally absorbs and releases moisture from its environment. This property causes wood to expand and contract in response to environmental conditions, particularly humidity levels. In large installations like sport courts and dance floors, these natural movements necessitate carefully planned gaps.

Types of Gaps

According to ASET Services’ research, gaps in hardwood floors fall into four main categories:

1. Shrinkage Gaps: These normal gaps (typically 1/32″ or less) occur when wood shrinks after installation, usually during winter heating cycles. Occasionally, they may reach 1/16″ in size.
2. Expansion Voids: These are intentional gaps (around 0.1″) left during installation to accommodate future wood expansion. They typically appear in a regular pattern every 8-12 flooring rows.
3. Large Gaps: Any gap exceeding 1/8″ (3mm) is considered problematic. These gaps compromise the floor’s structural integrity and can pose safety risks to athletes and dancers.
4. Crush Gaps: These permanent deformations occur when excessive expansion causes the wood to crush at the edges. They often result from severe water exposure and indicate permanent damage.

Environmental Control: The Key to Gap Management

The size and frequency of gaps can be minimized through proper environmental control. The Maple Flooring Manufacturers Association (MFMA) recommends maintaining relative humidity between 35% and 50%. For optimal results:

• Facilities should run climate controls 24/7/365 when possible
• Some regions require both dehumidification and humidification
• Installation timing and wood moisture content should be carefully planned

Real-World Examples

Consider these scenarios based on ASET’s calculations:

• In a facility maintaining MFMA’s recommended humidity range (35-50%) with maple installed at 7% moisture content, minimal shrinkage occurs and only small expansion voids are needed.
• When summer HVAC shutdowns allow humidity to reach 65%, the same floor requires more frequent expansion voids to accommodate increased wood expansion.
• In drier regions, with humidity fluctuating between 20-35%, shrinkage gaps become more prominent than expansion concerns.

The Bottom Line

While gaps in hardwood sport and dance floors might seem concerning, they’re often a sign of proper installation and necessary for the floor’s longevity. However, gaps exceeding 1/8″ should be addressed promptly as they can compromise both structural integrity and user safety.

This article is based on research by Dr. Paul W. Elliott, PhD, PE, owner and President of ASET Services, who has over 30 years of experience in sport surface design, manufacturing, research, and testing. The original white paper “GEN-007: Gaps in Hardwood Sport/Dance Floors” is licensed under Creative Commons Attribution-NoDerivatives 4.0 International.