Why does moisture warp wood

Why does wood sometimes look twisted and warped?

If you've ever gone to the hardware store to buy wood to build those DIY desks or home theater centers, you're probably on your fair share of warped and twisted boards

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If you've ever gone to the hardware store to buy wood to build that DIY desk or home theater center, you've likely stumbled upon your fair share of warped and twisted boards before you finally landed on a decent-looking 2 × 4 . Here's why that is.

How wood is made

To really understand why wood sometimes turns, bends, and warps, it is important to first learn how wood is made.

Wood comes from logs that are passed through a series of industrial size saws and cut into more manageable pieces. The graphic above is a great example of the various shapes and sizes that can be achieved with a single log and different types of cutting methods.

Trees are naturally moist from the inside. When logs are cut into smaller pieces, they need to dry out. Depending on where the wood is made, it is either air dried or oven dried.

Air-dried wood usually starts out in the open and is laid out with spacers between the pieces to allow airflow all around. Once the moisture level drops, it is sometimes left to dry indoors and the wood used to the indoor conditions. However, sometimes it is left outside to acclimate to the outside conditions, making it more suitable for patios, fences, and patio furniture.

Oven dried wood is oven dried (obviously) but is more expensive. However, it is much faster than air drying and absorbs more moisture, so oven-dried wood is usually less prone to twisting and warping.

As soon as the wood has dried, it is fed into planes. These are unique types of saws that shape the wood into the perfectly rectangular shape you are familiar with, and from there it is sorted into specific sizes and shipped to your local hardware store for purchase.

How twisting and warping occurs

As mentioned above, each drying method has advantages and disadvantages. Depending on what you are going to use the wood for, you may want to opt for a specific type of dried wood. However, both methods can be carried out incorrectly, and this can lead to severe twisting and warping.

First of all, there is no way you can completely prevent wood from twisting and warping, even if you get everything right. Wood acts like a sponge and expands when it absorbs moisture from a high humidity environment. And then it shrinks and hardens as it dries out and gets used to a lower level of humidity. This leads to varying degrees of twisting and warping.

However, if you dry out the wood properly, you can at least significantly reduce the chance of wood warping or twisting. One of the reasons you see all kinds of warped boards in the hardware store is that when you took them out of the oven they probably weren't completely dry. While they were being delivered to the hardware store, the wood dried out, but in a different environment, causing twisting and warping.

This will avoid twisting and warping

Again, you can't always avoid the twisting and warping, but there are some steps you can take to reduce the chances of this happening, both during the buying process and after you bring it home.

First, find your lumber at the hardware store when you go through everything. You know that a board is sawn timber when decorative rays shine through on the surface (see illustration above). Quartersawn lumber is usually sturdier than lumber cut using other methods.

Even if you've found a really straight piece of wood, you'll still want to take some care of it after you bring it home. Leave it in your garage or shop for a couple of weeks and make sure there are some spacers underneath to allow air to get to the underside of the boards. This way the wood can get used to its surroundings. If you find that it starts to warp and twist, it's no problem for you to return it and get your money back. This is a lot easier to do before you cut everything up.

If you want to avoid constantly looking for wood to find good planks, you should check out your local lumber yard, which likely has higher quality wood than a large store like Lowe's or Home Depot - these larger stores are usually more about quantity than order Quality worried.

Image by Core77, Mike Mozart / Flickr, Luke Gilliam / Flickr