It’s nearly winter. That means that your hardwood floors are about to show cracks between the boards. If you’ve moved into a new house, these cracks could cause alarm. How could your brand new hardwood floors crack?

Gaps in Hardwood flooring

Gaps in Hardwood flooring

Gaps between boards, or cracks, if you will, are not the result of the wood floor failing or falling apart. They are the result of the wood planks shrinking as the relative humidity goes down and the wood floor loses moisture content. The air in the summer has a higher relative humidity than in the summer. This lets the wood flooring absorb moisture and swell. So usually gaps between boards go away in the summer. Then those gaps reappear in the winter as the humidity goes down again.If your builder had installed the floors with too little moisture content at the time of installation, when the relative humitidy went up, the boards would have nowhere to swell or expand and they would push against each other causing the planks to cup and possibly rise. Flooring must be installed to allow this seasonal swelling and shrinking.

If you have standard, 2 1/4″ wide flooring, you should not have gaps wider than the thickness of a business card. However, sometimes two or three boards will stick together and move as a unit. This would produce one crack the width of the thickness of three business cards instead of three cracks, each the with the thickness of one business card. This would be considered normal. If you have cracks wider than that, chances are the floor was installed with too high a moisture content.

If your flooring consists of wider planks, your gaps will be proportionately wider. The wood will shrink the same percentage, but the actual dimension of the crack will necessarily be wider. Planks twice as wide will produce gaps that are twice as wide.

Engineered flooring shrinks less than solid wood flooring. This is because engineered floor has a solid wood surface, but the underlying wood is actually plywood. Plywood is dimensionally more stable because it is assembled with the wood grain of each layer running ninety degrees to the layer above and below. Wood shrinks across the grain and not much with the grain. So one layer reisist the shrinkage of the neighboring layer. If you want wide plank floors, take a hard look at engineered flooring. It will remain much more dimensionally stable than solid wood planks, yet the surface, the part you see and walk upon, will be identical to the solid plank.

Filling the gaps is merely a temporary cure. When the wood swells again as the season changes, chances are the filler will be squeezed out. My recommendation is to look around at older houses and observe the gaps in those floors. It’s likely you looked right past those blemishes and maybe even viewed them as part of the “patina of age” and thought they enhanced the charm of the house. Your house will develop it’s own patina and grow more charming every season if you let the nature of wood take its course. Your wood floors are a natural product that abides by the laws of nature. Swelling and contracting with moisture content is the natural behavior of wood.

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