Wood fences like picket fence wraps because of changes in moisture content that causes them to distort and become impractical. To be specific, it is when a part of a wooden fence dries faster than the other parts causing them to shrink faster.
The science behind this is the relationship between the humidity in the air and the wood’s moisture content. Fence Boards Warping happens when it has high moisture and it constantly shrinks until it reaches a balance with the air’s humidity, this process is otherwise called equilibrium moisture content (EMC). On the contrary, when the wood has a low moisture content, it absorbs moisture from the surroundings causing it to swell until there is equilibrium.
The process of EMC can take days, weeks, and months, factors such as the size of the wood, its grain and coating, and air temperature contribute to the length of time.
There are certain types of wood that are more resistant to warping such as Cedar, it is the type of wood that is very compact and naturally resistant to breaking because of moisture. Another type of wood that has a straight grain pattern is Redwood, it has a natural chemical that prevents absorbing moisture that causes wood to swell. Lastly, Fir is a type of wood that is robust and can prevent warping or shrinking. Pressure-treated wood also lengthens its life and shields itself from termites and fungal decay.
Choosing the right lumber is one thing, but what else is important?
Look for wood that has straight grain patterns for they are less likely to warp, wood that is also cut off from the center of the tree is also known to be much more durable and can fight against deformity. Sawing techniques and the process that wood goes through also affect its quality.
How you store and maintain your wood also affects its ability to process EMC. Boards should be stacked based on their thickness and stickers must be vertically aligned and remain flat. While stacking weights on top of lumber can hinder it from cupping, it’s advisable for wood to be exposed to air for proper ventilation. Finally, wood should be placed in a dark, cool, and dry environment and should be wrapped if humidity is above 80% to limit moisture absorption which makes it warp.
Drying and curing can minimize warping, Kiln drying is one known technique that prevents wood from warping while still being able to adapt to the air’s humidity. It is also important to note to quickly dry and not over-dry your wood to prevent it from breaking.
Moisture can escape through the ends of the board 12 times faster than any of its surfaces, sealing the ends can balance out the process of EMC throughout the board which lessens its ability to shrink or warp.
Stains or paint serve as an additional layer that regulates moisture absorption.
Wood warping is already a common problem for those who handle them. As stated above, there are factors that come into play to prevent them from warping or shrinking. Now that you’re equipped with the knowledge, you can better take care of your precious wood fence.