If you’ve ever had to do your woodwork in a particularly dry or humid area, then you’re probably familiar with the kinds of havoc it can wreak on your projects. Joints will shift, fastenings will become less secure, and boards will warp. While managing humidity may seem like an impossible task, there are steps you can take to ensure that your work environment works with you, rather than against you.
In the US and Canada, maintaining anywhere from 30% to 40% relative humidity (RH) in your workshop is best, since most areas in this region have an average humidity level of 37%. The most important factor to consider is where your finished piece will end up, because if the location it ends up at has a significantly different relative humidity than your workshop, it is very likely that it will warp.
Why Humidity Matters For Woodworking
Humidity is important to your workshop because it will affect the quality of your finished product. All wood contains a certain percentage of water, and it will release or draw in water based on the relative humidity of its environment. If you work in an environment that is more humid than the wood’s moisture level, then the wood will draw in water from the air, causing it to swell. If you work in an environment that is drier than the wood, then the wood will release water into the air, causing it to shrink.
If you’re familiar with the preciseness of carpentry, then you can quickly see how your materials changing shape and size would be a serious problem. While both swelling or drying of your project pose an issue, drying is generally more severe, as it can lead to cracking, checking, and other damage throughout the product’s lifespan. Swelling usually doesn’t cause these sorts of issues. However, swelling can be problematic if your product’s destination is significantly drier than your workshop. The person who ends up with the finished piece will be faced with cracked and damaged wood once the swelling goes down, hurting your reputation as a carpenter.
This is why trying to match the humidity of your workshop to the humidity level of its destination is important. If you’re just building a bench for your own kitchen table, then your workshop’s humidity is probably close enough to your kitchen’s humidity that no significant swelling or shrinking will occur. However, if you’re working in Florida and building a bench for someone in Colorado, then you will definitely want to adjust your shop’s humidity levels to more closely match those of Colorado so that your customer doesn’t end up feeling cheated.
How To Control and Reduce Humidity
So let’s say that a nice couple from Colorful Colorado has in fact ordered a one of your benches from the muggy swamps of Florida. How do you alter the humidity of your workshop to improve the quality of life for your product?
Well, first of all, you need a way to know how humid your shop actually is. There are lots of simple RH detectors out there, most intended for home and office use. While these work fine, having a reliable electronic RH detector is better, and having a few is best since you will be able to compare their accuracy against each other. The other factor you need to consider is the moisture content of our lumber. Since the average relative humidity of North America is 35%, a moisture content of 6% to 7% is good. The higher the relative humidity, the higher moisture content you want your lumber to have.
Once you know the RH of your workshop, the RH of your product’s destination, and the proper moisture content your lumber should have for that destination, you can start to work on adjusting your workshop’s RH. Having your shop sealed as best as you can is very important. The more you have between your shop and the outdoors, the more effective your efforts to reduce your shop’s RH will be. For a list of some of the products that have helped me control the temperature and humidity in my shop, take a look at this page.
The simplest way to reduce the humidity of your workshop is by using a dehumidifier. Lots of a/c’s have this as a built-in feature, but if yours doesn’t (or you don’t have one) then you can buy a dehumidifier for your workshop. Keeping the temperature of your shop cooler is also ideal since cooler air doesn’t hold moisture as well as warm air does. Adding vents to the top of your shop also works as an effective means for reducing moisture. Since warmer air holds onto moisture, creating vents will allow that warm air to escape your shop, taking some of the humidity with it.
Working In High Humidity Environments
For the most part, these measures should be enough to manage your shop’s relative humidity. However, if you live somewhere that has abnormally high levels of humidity, your woodworking will be affected more significantly. Humidity levels are usually more severe in coastal and tropical areas, as well as warmer times of the year.
Something you may have encountered before (especially if you used lumber from a different region) is your wood warping before you’ve even seen a project to its completion. This happens because the wood is adjusting its moisture content based on the RH and temperature of your workshop. The way to combat this is to give the lumber some time to acclimate to your setting before you begin working with it. A good rule of thumb is to wait two weeks before working with wood that’s new to your shop. The more time you can add to that, the better. Also keep in mind that different kinds of wood will react differently to the RH of your shop, so when working with a new type of wood be sure to do the necessary research to ensure your project’s success.
Another issue that carpenters working in humid environments are likely to encounter is rusting. While tools inevitably rust over time, the process is rapidly sped up in more humid environments. Fortunately, there are some precautions you can take to slow down the process. Keeping your tools clean and dry after every use will help, since dirt can retain moisture. Once you’ve finished drying them, oiling them will further help, since oil will prevent water from coming into contact with the metal. For storage, a sealed toolbox is always best. There are lots of great options available for purchase, and even some that are specially equipped to counteract the adverse effects of a humid
Other Factors To Consider
While this covers most of the things you should keep in mind when working in a more humid environment, there are other factors that you can address to further improve the quality and lifespan of your project.
The orientation of your lumber’s grain has a pretty significant impact on how much it will warp when it changes moisture content. Wood is primarily cut using two different methods: Flat sawn and Quarter sawn. Most of the wood you buy, especially if it’s over the counter, is going to be flat sawn. However, flat sawn wood will warp much, much more than quarter sawn wood will. In fact, wood that has been quarter sawn will warp half as much as flat sawn wood. Always purchase quarter sawn when possible in order to reduce the likelihood of damage later on.
Also be aware of how the wood you are purchasing was stored. If your purchasing wood that was stored outdoors, it will take it much longer to acclimate to the environment of your workshop. Working with wood after it was stored like this has a much higher chance of warping during the construction process. Opting for wood that has been stored in a temperature controlled environment will reduce this likelihood, as well as the time it takes to complete your project.
If your project involves using wood glue, the quality of glue you use will also matter. Wood glue will be less effective and could even dissolve in more humid environments. If you’re working in a humid environment or sending your project off to a location with high levels of humidity, buying wood glue that is more water resistant will make sure that your piece doesn’t come undone over time. You can slow down the effects of moisture absorption by using a high-quality finish on the wood. Just bear in mind that it can’t stop these effects completely.
The best way to counteract the effects of moisture content changes in your lumber is to determine the RH of the location it will be sent to. It’s also extremely important to give your wood time to acclimate to your workshop environment. While two weeks is “enough” time, some carpenters recommend timelines as long as two years.
While woodworking in a humid environment definitely poses an added challenge, you can keep these factors in mind throughout the process to create a more solid finished product and keep your reputation intact.