What’s the weather for the weekend going to be? Will it be hot? Cold? Rain? Snow?
We care about the weather because we are very much affected by our environment. You may not think about it very often, but everything made of wood is also affected by weather. Have you heard your house cracking and popping as the seasons change? Or perhaps you have a door that sticks in summer but is fine in winter? You need to understand a little about weather and wood to make sense of it.
Wood is a pretty challenging building material; it burns, it rots, its strength varies depending on which way the grain is oriented and it is sensitive to temperature and humidity. Heat will make wood expand and cold will make it shrink, potentially causing cracks or loose joints.
Then there is humidity – wood also expands and contracts as it takes on or loses moisture. Many beautiful wood projects have been ruined because high humidity caused the wood in the finished piece to soak up moisture. The other extreme – a dry climate, will pull moisture out possibly causing cracking or warping.
So whether you are a woodworker or the owner of fine wood furniture you should be aware of environmental effects. Here are a couple of factors you need to understand about humidity:
Absolute Humidity describes the actual amount of moisture in the air and is expressed in grams per cubic foot. The ambient temperature determines the maximum amount of water vapor the air can hold. At higher temperatures air can hold more moisture and conversely at lower temperatures it holds less.
Relative Humidity is the percentage of the amount of water in the air relative to the amount that could be in the air, given the current temperature.
The surrounding air is the primary source of moisture affecting your wood products. The moisture level in the wood and the surrounding air will always seek equilibrium.
The relative humidity will determine whether you can add or subtract moisture to keep your home in balance. The wood in most homes will average about 8% moisture content, higher in more humid areas and lower dry climates. In most homes wood will experience changes in moisture content as the weather changes. It can withstand brief changes but high or low extremes and rapid changes will likely cause loose joints, cracks, raised grain, dull finishes, or other damage.
So what can you do?
- Protect your wood with a good, well maintained finish. Finishes slow the transition of moisture in and out of wood, although they do not stop it.
- Close the house when the weather is extreme. When it’s dry in winter, add moisture with a humidifier. In the summer, use your air conditioner to reduce humidity.
- If you are a woodworker, design your projects with the future movement of the wood in mind.
Remember that your furniture and other wood products care about the weather too.
