Does Wood Expand In Heat?

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When working with wood, newbies should know how temperature and humidity affect the material in terms of quality and durability. Wood can swell and shrink depending on the moisture level of its fibers, but it can also be due to a different reason.

If you want to know if wood expands in the heat, our woodworking experts are here to share what you need to know.

How Does Wood React To High Temperatures?

Although the temperature is not directly the cause of wood expansion and contraction, it plays a significant role in the moisture content of the wood.

The rise and fall of temperature in the environment indirectly control the amount of water inside the wood, resulting in either expansion or contraction.

Does Wood Expand and Contract Due to Humidity?

First, wood is hygroscopic, which means it absorbs moisture from the air.

wood with lacquer finish

The wood will absorb moisture from the surrounding atmosphere if you live in a relatively humid area. On the other hand, it will release moisture if the wood has more water than the air around it.

As the wood settles in its environment, it will eventually reach a point when it stops releasing and absorbing moisture. It will have a balance in the moisture level with its environment, and this state is called the Equilibrium Moisture Content (EMC) [1].

Whether you are a contractor or a person who wants to incorporate wood into your home, you should know that moisture can affect a wood’s size. However, this change is temporary.

Wood will increase in physical size as the moisture content increases. These movements may result in the following wood conditions:

hemlock wood

Additionally, these are the different types of warping that you might see in your wood materials:

Wood can reach the EMC after a few weeks or months, where it will stop changing in size depending on the atmosphere.

Does Wood Expand and Contract Due to Warm Temperatures?

Wood expands when subject to warm temperatures, but the main reason it happens lies in the air’s moisture level. Warm air tends to hold more moisture, and the wood fibers absorb more humidity until it balances their moisture level with the atmosphere.

wood finishes

Other than humidity and temperature, these are the additional factors that might contribute to this process:

Wood movements are unique and usually vary depending on the conditions in which it is exposed. Based on our experience, it is safe to say that wood will expand when exposed to heat or hot temperatures.

How Much Can Wood Expand In Hot Temperatures?

Typically, wood has around 8% to 20% moisture content and can expand for a quarter for every 12 inches of width. Contrarily, the length of the wood usually remains unaffected by constant expansion and contraction.

Our woodworking team suggests that you allot enough room for movement when using this material in construction. 

wood finish by heat gun

Another thing that you should know is that wood expands in a predictable pattern. Knowing the direction it’s likely to expand to can help give you an idea of where to leave room for its movements.

Does Wood Tend to Expand in the Summer or Winter?

Wood mainly expands during the summer and will then contract during the winter.

Cold air is less humid than warm air, so there will be less moisture to absorb for the wood. Wood fixtures will also release moisture content to balance it with the atmosphere. 

However, warping and swelling can also happen if the wood is exposed to freezing temperatures.

If the cold air is wet, specifically during rainy days, the wood fibers will gather as much moisture as possible until it reaches maximum saturation. The moisture content can remain at that level unless the weather dries it.

wooden furniture applied with beeswax

Then, the water in the wood fibers will freeze during the winter. This will push the fibers apart, eventually leading to warping and swelling. It mainly happens when the moisture does not have enough time to release before it gets frozen.

That said, it is evident that the humidity levels in the atmosphere play a more significant role in the wood expansion and contracting than the temperature. 

How To Prevent Wood From Expanding

Wood expansion is inevitable if you live in a humid area since it is its natural process. Unfortunately, it usually affects furniture and other wood products negatively.

Remember that even the slightest movement of wood, whether expansion or contraction, can significantly change the appearance of your furniture and other fixtures.

These are the things that you can do that would help keep wood from warping, swelling, and other forms of expansion:

wood finish sealer

Seal The Wood

Although there is no guarantee that sealing wood would prevent it from expanding, it can still help minimize the effects of humidity.

It is only natural for wood to absorb moisture, but using a good seal such as epoxy resin can help make it airtight.

Once the wood is sealed, it will not absorb as much moisture as it usually does when exposed. It will also experience less swelling but don’t expect this process to stop the wood movement altogether.

Deconstruct Furniture During Extreme Weather Conditions

If the wood is in your outdoor furniture, it would be best to deconstruct them during extreme weather conditions. Leaving them outside through harsh winters can take a toll on their appearance.

You should have storage that would protect your wood furniture from such elements. It could be your garage or basement, as long as these places are not subject to excessive moisture in the atmosphere.

It’s better to start deconstructing your furniture during the later months of fall so you won’t have to do it when it’s already freezing outside.

exterior furniture

Aside from winter, you should also protect your wood furniture from heat waves. Too much heat can expand it as it dries and cause it to crack.

The excessive variations of wood movement can permanently damage the furniture’s wood joints, even if they are made from strong materials. They can eventually break and develop cracks.

Secure The Furniture And Avoid Exposing It Outside

If you don’t want to disassemble your wood furniture consistently, you can opt for a weather-resistant cover for them. Keeping them from getting in contact with water can limit the wood expansion.

This process will also maintain the quality of the furniture and keep them looking new for as long as they can. Allowing wood to get soaked in water from rain and other conditions can significantly affect its state, not in a good way. 

If you keep them in a box during rainy days, keep them with an additional cover as protection from humidity. Such actions will allow you to use the furniture for a long time. 

moving furniture

Use Premium Furniture

If you want furniture in your home to last, always purchase high-quality products. There are many options for furniture out there that you can get at a much lower price, but there’s no telling when you’ll be able to use them.

Cheaper furniture is usually made of softwood. They cost less, but hardwood is more durable. Softwood is also more susceptible to dry rot, which can spread through other materials.

Opting for more expensive furniture means that you are also paying for their longer lifespan. Premium products often last longer, even if exposed to extreme weather conditions. It may last years, and you may even be able to pass it down through generations.

Luxurious furniture is an investment for your home. This also lessens your worries about excessive damage if they get wet.

Does Wood Enlarge During Hot Months?

Yes. It is usual for wood to enlarge during the hot months, especially if you live in a high-humidity area. This thermal expansion can cause warping and swelling, potentially altering the wood’s appearance.

pine wood furniture

During hot weather, there is more moisture in the atmosphere for the wood to absorb. The wood will then store the moisture in the pores of the wood fibers, causing it to expand.

For example, the higher relative humidity might make it more challenging to close a wooden door during the summer.

At What Temperature Does A Wood Warp?

Wood warping does not necessarily happen at a specific temperature. Many factors contribute to it, such as:

Warping happens mainly when the moisture content of the wood is scattered unevenly. When one area dries faster than the other, it will also shrink faster.

That creates stress points in the wood, thus creating a warping shape.

wood warping twist

Does Wood Contract in Cold Temperatures?

Yes. Wood shrinks in colder climates due to the drop in humidity levels in the atmosphere. This difference causes wood to disperse its moisture throughout the wood fibers and reach the equilibrium moisture content. 


Wood does expand in the heat and it is one of its natural characteristics, and there’s no way to take that away from them.

Coating and seals are a great way to limit this process, but wood will always be bound to absorb moisture from its surrounding atmosphere. Fortunately, this doesn’t last forever, and there are many ways to prevent wood furniture and fixtures from permanent damage.

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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