When building a deck, it is important to be aware of the various types of wood defects and how they can impact both appearance and performance. Perfect pieces of lumber are rare or even non-existent, as most lumber typically contains defects.
Lumber defects can occur either during tree growth or after trees have been harvested and processed. In order to prevent these defects, it is crucial to buy lumber of higher quality in the first place, as all lumber undergoes grading.
To ensure proper installation, it is important to let the wood dry thoroughly, particularly when pressure-treated lumber is used. When it comes to deck boards, using protective stains can serve multiple purposes – hiding visible flaws and slowing down the drying process, which can help prevent or minimize defects like checking from worsening.
Types of Natural Wood Defects in Deck Boards
Warping
Warping of a piece of lumber refers to any deviation from a flat surface, which can happen as a result of variances in wood shrinkage along the radius, tangential, and/or longitudinal directions or when growth stresses cause the board to distort.
Checks and Splits
A check is a crack that can be found on the surface of a board and typically runs lengthwise. The primary reason for this occurrence is when the lumber dries too rapidly. Checking enables water to penetrate the board past its pressure-treated surface, which can hasten the deterioration of the board.
Splits have the ability to run completely through the board, unlike checks, and if a split is severe enough, it can render the board useless. In certain cases, split boards can be salvaged by ripping or cutting them to preserve a section of the board.
Pecking
The most common occurrence of pecking is in cypress. It manifests as a dark shallow cavity or pitted area on lumber and is caused by a parasitic fungus. The decay ceases once the tree is harvested. Woodworkers often actively search for cypress with “pecky” or “peggy” characteristics because of the visually pleasing unique texture it adds to the surface.
Rot and Decay
Decay, known as rot, is a frequent type of disintegration of wood fiber caused by microorganisms such as mold and fungus that sustain themselves by consuming the wood. For fungi to prosper, they necessitate four specific conditions: presence of oxygen, temperatures ranging from 40° to 100°F, moisture levels of 30% or higher, and a source of food in the form of wood.
Woods such as cedar and redwood possess natural substances known as “extractives” which add resistance against rot. Pressure-treated wood is infused with chemicals that are harmful to fungi and molds. Several stains incorporate mildew inhibitors to aid in preventing decay. Ensuring that your deck remains dry before and after installation is the most effective method to avoid decay.
Pith
The spongy center of the tree, known as pith, can be problematic if it is present on the surface of a board. Pith has a diameter roughly equivalent to a pencil, measuring about ¼ inch. Additionally, the first three or four growth rings surrounding the pith should be approached with care. When these sections dry out, they tend to expose and distort at the edges. It might be possible to remove this portion of the board and still utilize it.
Ring Shake
Cracks known as ring shake occur between and run parallel to the growth rings of a tree, resulting in the weakening of the wood. In addition, there may be dark discoloration and an unpleasant odor resembling vinegar or rancidity. This issue arises due to parasitic bacteria and is more commonly found in wood with a significant moisture level.
Streaks
Mineral streaks, also known as streaks, may cause boards to become discolored. These streaks occur when dark-colored minerals are absorbed into the tree through its water source or due to mold growth. Typically, the streaks appear in shades of blue or brown and can either be eliminated by cutting them out or hidden using a dark stain. For streaks caused by mold, cleaners that contain oxalic acid are effective in their removal.
Insect Damage
There are numerous insects that consume and reside in wood. Common examples include beetles, moths, and wasps. Additionally, borers are also prevalent. These borers typically act as “secondary invaders” and are drawn to wood that is already weakened, damaged, or nearing the end of its life.
Wood that has a moisture content higher than 30% is attractive to wood-boring insects. These insects create round holes in the wood and disperse their excrement, which resembles sawdust, in a random pattern.
Pitch, Gum and Sap
Resinous substances, which are natural components of trees, have the ability to accumulate in pockets within a board, usually in the vicinity of a prior tree injury. The presence of resin and sap in lumber has the potential to lead to staining and could pose challenges during the application of finishes.
Wane
The presence of bark or the absence of wood at the corners of a board is what is referred to as wane. Wane is only found in lower-grade lumber and in certain situations, flipping the board can be done to hide this flaw.
Crook or Crown
When a board is bent end-to-end, either due to uneven drying or because of the presence of the trees’ piths at the board’s edge, it is known as a crook or crown defect.
If you want to obtain a narrower straight board, one option is to tear the board apart. Alternatively, you can pass it through a jointer multiple times. Whenever you are removing the outer area of a deck construction pressure-treated board, make sure to apply an approved topical chemical treatment to the edges or ends.
Bowing
Bowing is a flaw that occurs when a board curves along the grain lines, rather than across them. If the board is placed on a flat surface, both ends will be lifted off the ground. This flaw usually happens due to unequal air circulation during the wood’s drying process. Bowed boards have internal tensions that make them challenging to cut, and attempting to rip them can be hazardous. To make a crosscut, it is advisable to have the bow facing upwards.
Cupping
When a board bends from edge to edge, forming a U-shape across its face, this is known as cupping. This typically happens to boards that are cut near the pith. In order to fix cupped boards, they can be ripped into smaller pieces and then planed. However, attempting to forcefully flatten a cupped board will probably result in cracking.
Twisting
The term “twisting” encompasses a board’s ability to bend in various directions, leading to an inability to maintain a straight line. On occasions, a corner may not align with the rest. Typically, this arises when the wood grain pattern is not parallel to the edge.
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Knots are formed when a branch or limb is broken or cut off from a tree, and they serve as the base of the remaining branch. These knots receive nourishment from the stem for a period of time, leading to the development of dark hard rings. As the knots disrupt the continuity of wood fibers, they become a weakness in the wood. There are various types of knots.
– Sound knots, also known as tight knots, are secure and cannot be dislodged because they are firmly attached to the wood structure through growth or position. They are partially or fully integrated with the growth rings. – Unsound knots, or loose knots, are knots that can fall out from the timber when pressure is applied or have already detached. These knots result from a dead branch that was not fully incorporated into the tree before it was harvested. – Encased knots are those that are not intertwined with the surrounding wood. – A knothole refers to a void left after a knot has been dislodged. – Spike knots are branches that have been cut either across or lengthwise, revealing the end or length section of the limb or knot. These knots typically exhibit splits and significant deviations in grain near them.
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Shakes, which can be found lengthwise in wood between growth rings, are cracks or separations that often continue along the board’s surface and sometimes penetrate below its surface. They can either partially or fully separate the wood fibers.
When appearance is important, the separations in the wood are considered undesirable. Shakes, which can be caused by frost or wind stress, are a naturally occurring defect. Additionally, shakes can occur during felling due to impact and shrinkage in the log prior to conversion.
There exist two types of shakes.
Star Shake, also referred to as heart shake, is a phenomenon where a group of splits appear in a tree in a star-like pattern radiating from the pith or center of the tree. These splits are wider on the outside ends and narrower on the inside ends. Star shakes are usually formed due to extreme heat or severe frost during the tree’s growth. Ring Shake, also known as “cup shake” or “wind shake,” is a type of rupture that runs parallel to the growth rings of a tree. This type of shake is not easily noticeable in green logs and lumber, but becomes apparent only after the drying process. It is caused by various factors, including bacteria, tree wounds, tree age, and environmental conditions such as excessive frost action on the sap when the tree is young.
Separate into distinct parts.
A split in the wood grain, also known as ring shake, is a rupture or separation that decreases the board’s appearance, strength, or usefulness. Ring shake is a common type of rupture where the separation runs parallel to the growth rings.
After drying, it becomes evident that green logs and lumber have a hidden issue that is not easily noticeable. This issue can be caused by various factors such as bacteria, tree wounds, tree age, and environmental conditions.
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Stains, which can be any color other than the natural color of the wood, are a result of a discoloration that penetrates the wood fiber. They can be caused by various conditions and are often attributed to non-wood destroying fungi. Certain stains might indicate the presence of decay or bacteria.
Spalting is a process that occurs when fungi invade wood and cause changes in its appearance and color.
Spalting is the term used to describe any form of wood discoloration caused by fungi. Normally, it is observed in deceased trees; therefore, if the wood is not stablized promptly, it will eventually decay. Pigmentation (“sapstain”), white rot, and zone lines are three types of spalting commonly used in woodworking to enhance design.
Dealing with Defects
The beauty or value of the finished product is often diminished when woodworkers use wood with defects, which is why many prefer to avoid it. However, there are some who highly value defects in their works.
For instance, Greg Heumann, a wood microphone maker residing in Geyersville, Calif., and Cecil Ross, a tree sculptor from Bainbridge Island, Wash., frequently search for wood that exhibits specific defects. They hold the belief that such flaws enhance the wood’s character and contribute to the overall quality of their final creations.
The woodworkers often depend on suppliers to deliver the specific wood they need. The majority of suppliers are trustworthy and take precautions to ensure that the wood they send to customers is typically without any deformities or irregularities.
Woodworkers who purchase wood from a lumberyard or big box store should, on the other hand, conscientiously examine the wood for quality and exclusively opt for pieces that are suitable. Additionally, they might need to obtain authorization to inspect the lumber and make a commitment to rearranging everything once finished.
However, not all woodworkers want to go through the process of sorting through stacks of lumber. Instead, they might choose to purchase the highest-grade available, regardless of whether it is necessary or not.
While premium furniture makers may opt for the best grade at times, woodworkers can typically save money and obtain high-quality wood by choosing lower grades. Frequently, lower-grade boards exhibit a greater degree of beauty and character compared to superior boards. However, the key to discovering these pieces is to possess a fundamental understanding of lumber purchasing.
There are woodworkers who may acquire wood from fence rows and fields, as well as old abandoned barns or other buildings. However, caution must be taken to avoid obtaining wood that may have bullets, nails, or barbed wire which could potentially harm a saw blade.
Defects may also have a supporting function, as long as they improve the aesthetic appeal of an item. For example, Landis seldom employs wood with appealing burls as a standalone slab due to its usual lack of stability. Instead, he transforms it into quarter-inch thick slices and affixes them to a sturdy backing within door panels or utilizes it as a veneer on furniture.
