Tip #39
Drying Your Own Lumber (continued)
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How To Air-Dry Your Lumber

The most important factor in air-drying is the air circulation. Although the basement may seem to be the perfect place to dry your wood, the opposite is probably true. Usually, the air in a basement is stagnant and humid. There is little circulation to remove the humidity. More often than not, green lumber stored in a basement will mildew and rot, rather than dry.

An attic on the other hand is usually too hot and will dry the wood too quickly. As I said before this results in surface checking. The wood on the outside of the board dries faster than the inside. As it dries it shrinks and cracks develop.

The best place to dry wood, believe it or not, is outside. Look for a spot that gets a breeze and isn't expose to a lot of direct sunlight. This will allow the wood to dry at a slow, even rate. You can build a simple drying rack, as shown in Figure 2. Make sure this rack is well off the ground and perfectly flat. Do not put the cross supports more than two feet apart or the boards will sag as they dry.

Once you’ve built the drying rack, you’re ready to stack the lumber. To allow proper air circulation between each board, you’ll need to put ‘stickers’ (small sticks) in between the rows to ensure proper air circulation. I use commercial furring strips for stickers, but any dry wood will do. The stickers should be as long as the width of the drying rack, at least ¾" thick, and no more than 1 ½" wide. The narrower the stickers are, the less likely they are to trap moisture and encourage fungus or rot.

Figure 3 . Paint the ends of the boards to prevent them from checking. If left unpainted, the ends will dry out faster than the rest of the board.

The structures within a tree -- the xylem phloem -- pass water up and down the trunk. Because of this, water leaves a board more quickly through the ends of the boards than it does through the faces and edges. This can result in the ends of the boards checking. (See Figure 3.) To prevent this, paint the ends of the boards as soon after they are cut as possible. This will seal the end grains and let the water leave the wood slowly and evenly. If the boards are all the same length, you can paint the ends after you’ve stacked them. If not, you’ll have to paint them before you stack them.

A note on sealing end grains: The Chapman Chemical Company, P.O. Box 9158, Memphis, TN 38109, manufactures a wax emulsion called Sealtite #60 to seal the ends of boards as they dry. It will work with both air-drying and kiln-drying processes, and comes in a variety of colors and container sizes.

Figure 4 . When you stack your green wood, don’t stack the boards edge to edge. Leave a space in between each board so that the air can circulate freely.

As you stack the lumber, arrange each layer so that it’s as wide as the layer beneath it. That way, each layer will be properly supported, and the weight of the boards from above and below will help to keep all the boards from cupping. Leave space in between the edges of each board to allow for air circulation. Positioning them too close together will keep boards on the inside of the stack from drying properly. (See Figure 4.)

Be careful to place the stickers directly over each other, in line with the supports. (See Figure 5.) Don’t stack the wood more than 4’-5’ thick. When you’ve finished, build a simple roof and lay it on top of the stack. This roof should have plenty of overhang, to keep the rain from dripping on the stack. If you can’t build your rack in the shade, paint the roof with aluminum paint. This will reflect the sunlight and prevent the stack from getting too hot.

Figure 5 . If you're careless about where you place the stickers, many of the boards will dry with a bad warp or bend. The stickers must be carefully placed one above the next, directly over the supports.

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