Wood is a sensitive element that rapidly changes its internal structure according to environmental changes. As woodworkers, we need to have a clear idea about how wood reacts in cold, winter, and summer. So, let’s find out, Does wood expand in heat?
Yes, Wood expands in heat because of the thermal expansion of wood fibers. Hot temperatures trigger the wood to absorb some amount of moisture into the wood to balance the moisture content outside resulting in wood expansion. Wood expands not directly because of heat, but for high atmospheric humidity.
But that’s just a quick snapshot of the question.
So, in this article we’ll dive into looking does wood expand in heat, what happens to wood when it gets hot, how much wood expands in summer or winter, how to stop wood from expanding, and more.
Furthermore, I’ll answer some frequently asked questions about does wood expand in heat as well.
Let’s dig in!
We’ve been hosing down our casks outside the distillery over the last few days because of the sunny weather ☀️When wood is subjected to heat, it can expand. This can cause warping, swelling and potentially shrinkage. 🥃 #glasgow #glasgowdistillery #scotchwhisky #singlemalt pic.twitter.com/138MyIu6Ma— The Glasgow Distillery Co. (@GlasgowDC) May 30, 2018
What Happens to Wood When It Gets Hot?
When the wood gets hot, it expands little because of the thermal expansion of wood fibers. Wood fibers are sensitive to temperature variations, and they expand in heat and shrink in cold.
But on the other hand, when wood gets hot the moisture content inside tends to evaporate into the atmosphere. This will make wood lose water and leads wood to shrink.
So, as you can see when the wood gets hot it expands due to thermal expansion and shrinks due to loss of moisture content. This indicates that wood expansion or shrinkage happens not because of temperature variations, but because of humidity changes.
When the outside environment (atmosphere) has high moisture content than the wood inside, the moisture will absorb into the wood resulting in wood expansion. Same as, when the atmospheric moisture content is less than the wood inside, the moisture inside of wood evaporates into the atmosphere resulting in wood contraction and shrinkage.
heat stains are literally just moisture that gets trapped in the pores of the wood and causes them to look rather unsightly— smoog. (new chapter out!!) (@aqoursaihara) January 4, 2022
BUT if you’re able to apply heat to the system, the pores of the wood will actually expand, opening them up to release the water! pic.twitter.com/szoz22QlaG
How Does Humidity Affect Wood Expansion and Contraction?
Humidity is the reason why wood expands and shrinks not the high and low temperatures.
When the outside is hot that means the moisture content outside is high (high humidity). In order to reduce the atmospheric moisture content and balance with the moisture content inside of the wood, the moisture absorbs into the wood. This concludes wood expands when the atmosphere is hot.
When the outside is cold means the moisture content outside is low (low humidity). In order to increase the atmospheric humidity and balance with the moisture content inside of the wood, the moisture will release into the air. This concludes, that wood shrinks when the atmosphere is cold.
Here’s how wood changes with atmospheric humidity,
|Atmospheric Humidity||The behavior of the wood|
|High Humidity||Wood expands|
|Low Humidity||Wood shrinks|
#factfriday – Did you know?…— coverbaloo (@coverbaloo) July 22, 2022
Creaks in your floorboards don’t actually have anything to do with the age of your house. It’s most likely a result of temperature and humidity changes that cause the wood to expand and contract. pic.twitter.com/f2ozszPme6
How Do Warm Temperatures Affect Wood Expansion and Contraction?
Wood expands in warm temperatures. Warm temperatures change the humidity of the atmosphere. When the outside air is dry and warm, that means it has low moisture content. In moist warm temperatures, the air has high moisture content.
When the warm air is drier than the wood inside, in order to balance the moisture content, moisture will evaporate into the air. This results in wood shrinkage. When water is loose from wood fibers, they tend to shrink.
In moist warm air, moisture absorbs into the wood resulting in wood expansion. when water absorbs into wood fibers, they tend to expand.
When you hear creaks, it’s more likely due to temperature and humidity changes within your home rather than its age. Wood is porous and can contract and expand with changes in temperature and humidity. 🏡#homeowners #insurance #coverage pic.twitter.com/arw2iksR2d— JR Isham (@jrisham) April 26, 2022
How Much Does Wood Expand In Heat?
Wood expands not because of heat; it expands because of humidity. Wood expands when the outside humidity is higher than the wood inside. The wood contract when the outside humidity is less than the wood inside.
The difference between moisture content inside of the wood and the atmosphere is known as relative humidity.
When the relative humidity is high, moisture absorbs into the wood resulting in wood expansion. When relative humidity is less, moisture releases from the wood resulting in wood contraction.
Usually, wood has 8% – 20% of moisture content inside. When it gets heated or under a warm humid atmosphere, wood expands ¼ inch for every 12 inches of its width. Quarter sawn wood expands 1/8 inch for every 12 inches.
Same as, when the wood is under a less humid atmosphere, it contracts ¼ inch for every 12 inches.
As you can see, the expansion of wood happens due to high humidity and the thermal expansion of wood fibers. The expansion amount is hard to notice.
Wood twists and warps due to irregular expansions of the wood. To keep wood from warping, you’ll have not to keep wood in extreme hot or cold weather.
Seasonal humidity change may cause the wood to expand and contract. pic.twitter.com/EXWR3S8mJw— Bromley Floors (@BromleyFloors) December 10, 2015
Does Wood Expand In Summer Or Winter?
Wood expands in summer and contracts during winter. When it is hot in summer, that means the air holds high moisture content. Therefore, the relative humidity of air goes down during hot months. In order to balance humidity in the air, the moisture absorbs into the wood which causes expansion of the wood. This is why wood expands in summer.
When it is cold in winter, the air holds low moisture content. Therefore, the relative humidity in the air goes up during cold months. In order to balance humidity in the air, the moisture released from the wood cause contraction of the wood. This is why wood contracts in winter.
This is a desk my dad made for me that I work at. The end joint is a dovetail, and the internals of the joint are designed to let the wood flex with the humidity; the end board will shrink slightly in winter, and expand slightly in summer. pic.twitter.com/1TyGNAPUzV— paul sanwald (@paulsanwald) November 28, 2019
How To Stop Wood Expanding?
Expansion of wood happens due to humidity changes which are so hard to stop since it is a natural process. But wood expansions can affect badly for furniture and other woodwork. Even a small movement of wood can damage the physical appearance of wood furniture.
Here’re some best steps you can take to keep wood from expanding,
- Sealing the wood
- Disassemble furniture in extreme conditions
- Cover up furniture and stop exposing it to outside
- Use high-quality furniture
So, let’s discuss each of the above steps separately to get a clear idea of stopping wood expansion.
1. Sealing The Wood
Sealing the wood with a proper sealer or stain product helps the wood avoid get contacting outside air. Use polyurethane resin, Epoxy resin as the sealer and apply several coats of it until the wood gets fully sealed.
Sealing the wood won’t absorb or release moisture to the outside world under humidity changes. Therefore, wood expansions will stop.
But I highly advise you to stop only wood expansions, but small movements of the wood. because wood is a hygroscopic material, and it needs to balance its moisture content with the outside environment. Small wood movements help the wood to prevent warping.
2. Disassemble Furniture In Extreme Weather
Better to disassemble your loving wood furniture during extremely hot and cold months to stop them from damaging due to wood expansions.
Wood tends to expand in summer due to low relative humidity and contract in winter due to high relative humidity. These excessive length variations can damage your furniture’s wood joints. Even though they are built from strong wood joints, they can easily break due to random movements under humidity variations.
Disassemble furniture and keep them in a safe protected environment until harsh weather is gone to use them for years without any issue.
If the environment becomes too humid, wood will absorb the moisture in the air and expand. pic.twitter.com/RLYnPijeqS— Hertfordshire Floors (@Fshertfordshire) November 11, 2016
3. Cover Up Furniture
Cover up furniture and stop them from getting in contact with water to stop wood expansions. This is super important for outdoor furniture because they can expand in rain.
Storage boxes should also cover up to stop cracking and splitting of the woods due to humidity variations.
Pro Tip: Acclimate your boards to their environment before installing.— CDA Wood (@CDAwoodllc) February 11, 2021
The boards are real wood and will contract/expand depending on the amount of moisture in their air. For more humid places, please let your boards sit for at least two weeks before installing. pic.twitter.com/HXmH3duGXb
4. Use High-Quality Furniture
High-quality furniture is built to tolerate wood expansions and contractions. They build from quality wood species that have good resistance against moisture and other outdoor elements. Those furniture can keep in outside without worrying much.
They have good resistance against environmental changes and impacts. With proper finishing and maintenance, they live more than decades even under harsh weather conditions.
Now you know everything about does wood expand in heat and how to prevent that!
So, let’s answer some frequently asked questions as well.
Does Wood Swell in Hot Weather?
Yes, wood swells in hot weather since moisture gets absorbed into the wood. during hot weather the moisture content in the atmosphere is high. due to low moisture content inside of the wood, the relative humidity decrease.
To balance the moisture content inside of the wood and atmosphere, the moisture will absorb into the wood and store in the pores structure of the wood fibers. This makes the wood swell. Wood swell results in wood expansion. This is why wood expands under hot weather.
@FamilyRoofing Temperature rises, so does the humidity in the air. This can cause problems for your roofing system. Humid air causes wood to swell and warp leading to problems with roof decking, support beams and joists. Humid conditions provide the environment for mold to grow. pic.twitter.com/oPcobgz1tl— Family Roofing (@FamilyRoofing) June 27, 2022
What Temperature Does Wood Warp?
Wood warp under extreme cold and hot temperatures. Wood does not warp around 70 – 72 degrees Fahrenheit under 50% of humidity.
Cold temperatures cause wood to contract. When the wood is contracting and expanding repeatedly, that can result in wood warping. Wood warping can be fixed by applying a proper sealer.
Hot temperatures also cause wood to swell, warp and twist. Plus, wood fibers expand under heat due to thermal expansion which can cause wood to warp under continuous movements.
Does Wood Shrink in Cold?
Yes, Wood shrinks in cold. During cold months, the air humidity is less. The outside moisture content is less than the moisture inside of the wood. Therefore, moisture tends to release into the outside air resulting in wood shrinkage. This is how wood shrink in winter.
In the cold winter days, wood tends shrink and may cause tiny gaps between boards. pic.twitter.com/aAdv93SK04— South London Floors (@FSSouthLondon) January 13, 2016
Did I cover all you wanted to know about: Does Wood Expand In Heat?
In this article, we have deeply discussed about does wood expand in heat and what happens to wood when it gets hot, cold, and in summer and winter. Plus, we have discussed how to stop wood from expanding and what steps we can take to protect wood furniture from damage because of expansions and contractions.
Wood expands in heat due to thermal expansions of wood fibers. But wood really expands not because of temperature changes, but because of humidity changes. When the air humidity is high, the moisture will absorb into the wood, and the wood gets expanded. When the air humidity is less, the moisture will release from the wood, and the wood gets contracted.
Furthermore, I’ve answered some frequently asked questions regarding does wood expand in heat. Hope you have gained good knowledge about how wood behaves in hot and cold weather. Don’t forget to apply things you have learned for your wood furniture under extreme weather conditions.