Drying wood correctly is essential or else your project could become a disaster. You may think all’s well when the project is completed but soon, glue joints begin to crack and different parts of the timber start to warp. Before you know it, the entire project is ruined and you have to rip everything up and start all over.
Most people purchase kiln-dried wood from their lumber retailer and while you’ll receive properly dried timber, it is likely to be expensive. If you learn how to dry wood at home, it could yield savings of up to 50%; a substantial amount if you’re planning a big project.
However, DIY drying is challenging as you need to learn the right techniques as well as having enough room for stacking and storing. Keep reading for some essential tips on air drying lumber.
Drying Wood – What You Need to Know About Moisture Content
This is the term used to denote the level of wetness in wood and it is expressed as a percentage. Believe it or not, this figure can exceed 100% because it is a representation of the ratio of water in a piece of timber to the weight to the timber when it’s totally dry. So if a piece of wood weighs 100 pounds but is 40 pounds dry, its moisture content is actually 150% as it contains 60 pounds of moisture compared to 40 pounds of dry wood.
Different species of wood have their own moisture content. Willow is one of the ‘wettest’ at 180% while white ash has an MC of 60%. Most wood-drying companies look to get the MC down to 25% then they use a kiln to drop it to 7-8%. Without a kiln, you should aim for an MC of 15-20% when air drying lumber then store it correctly so its moisture content falls low enough for it to be used.
You must also understand the concept of equilibrium moisture content (EMC). Your timber is said to reach EMC when it is in balance with the moisture of the environment it is in. Therefore if you store it in a wet environment, it will get wetter and damper until it reaches the moisture level of its surroundings. It goes without saying then that proper storage is essential.
Seal the Ends
Timber straight off the sawmill is at its wettest so you have to act quickly and move the wood into storage. Remember, wood shrinks when it dries so always look to cut the planks longer than your preferred size.
What you must be wary of is drying wood too quickly as this causes it to split. The ends of the planks will dry up to 10 times faster than the rest of the wood. In order to prevent this from happening, you have to seal the endgrain to force it to dry at a similar speed to the rest of the wood. There are specialist sealers on the market but you can also use latex paint or paraffin wax.
Store & Stack
According to research by the U.S Forest Service’s laboratory, green boards an inch thick will take up to 60 days to air dry to 15-20% moisture content assuming they are stored in a sunny and temperate climate. In colder and damper locales, it could take 3-4 months.
Store your wood in an open area free from damp but avoid placing it in direct sunlight. You can make the stacking process easier by ensuring the wood is cut in uniform thicknesses and lengths. Stack the timber in a way that makes sure it is exposed to air on all sides. You can place small pieces of wood (called stackers) between the planks to boost ventilation and dry the timber evenly. A useful tip is to add weight to the top of the stack to prevent distortion or warping.
After the stack has reached EMC, you can dry it further by moving it into a warmer location such as a heated basement or shed. If you’re using smaller pieces, you can invest in a drying cabinet.
Don’t cut the wood down to size until it has achieved the right moisture content for your purpose. I recommend investing in a moisture meter which is an excellent method of determining if your wood is ready to use. It measures electrical resistance, the higher the resistance, the lower the MC. Drying wood at home requires planning and patience but if you follow the above advice, you’ll do it properly and save yourself a small fortune when compared to purchasing kiln-dried wood.