April 28, 2025
Not much wood is perfect. In fact, most wood has defects. When making a deck, it’s important to understand the various defects in wood and how they can affect how the deck looks and how it will be used.
Lumber can have defects either during the growing process or after it has been cut and treated. All lumber is graded according to its quality. Purchasing highly rated materials from the start is the best way to avoid problems with your lumber.
Allowing the wood to dry completely before installation is also helpful, especially when using pressure-treated wood. Protective stains not only hide defects in deck boards but also stop or slow the development of defects such as cracks by prolonging the drying process.
Table of Contents
Any change in the wood boards from one plane to another is known as warping. It occurs when the boards twist due to residual growth stresses or when the wood shrinks in different ways along its length, width, or radial planes.
Splits are cracks in the surface of a board, usually in a straight line. It is usually caused by the wood drying out too quickly. Splits can accelerate damage to the boards by allowing water to enter the interior of the deck from the pressure-treated deck surface.
On the other hand, splits can run all the way through the boards, and severe splits can render the boards useless. Sometimes, a split plank can be saved by cutting it.
Capped with an HDPE layer, Capped Composite Decking is made excellent at resisting stains, scratches, weathering, and fading.
View MoreMost woodpeckers live on cypress trees. The disease, which appears as a small black hole or pit in the wood, is caused by a parasitic fungus. After falling, the tree will no longer die. Many woodworkers look for “woodpecker” or “woodpecker” cypress because of its interesting wrinkled surface.
The process of decomposition of wood fibers is called rot and is usually caused by tiny organisms such as molds and fungi that eat wood. Fungi need air, temperatures between 40 and 100 degrees Fahrenheit, at least 30% moisture, and a food source like wood to grow.
Woods like cedar and redwood have natural “extractives” that prevent them from mold and rotting. Pressure-treated wood has chemicals added to it that are harmful to fungi and mold. To prevent rot, many paints contain mold inhibitors. Don’t allow your deck boards to get wet before or after you lay your deck. This will help prolong their life.
The pit is the soft part in the middle of the tree, and if it is present in the boards, it is a defect. The pith is about 1/4 inch wide and as thick as a pencil. Be careful with the first three or four growth rings around the pith as well. These sections will open up and curl at the edges as they dry.
Cracks that appear between and along the growth rings of a tree are known as annual ring jerks. This can be detrimental to the strength of the wood. Black spots and an odor similar to vinegar or rotting food may also appear. This defect is caused by parasitic bacteria and occurs mostly in wood with high moisture content.
Mineral streaks are the name given to faded spots on some boards. They occur when dark minerals enter the tree from a water source or when mold grows. Some streaks are blue or brown in color and can be masked or removed with a dark stain. Cleaners containing oxalic acid can remove mold streaks.
There are many bugs that live in and eat wood. Diamondbacks, beetles, moths, wasps, and other insects are common. Moths are usually “secondary invaders” that are attracted to wood that is already weak, damaged, or dead.
Wood-eating insects leave behind feces that look like sawdust. The holes they make are usually circular and distributed in different locations in the wood. Insects are usually attracted to wood with more than 30% moisture content.
Trees naturally contain these sticky substances, which collect in cracks in boards, usually where the tree has been injured. The wood can become soiled with resin and sap, making it difficult to apply finishes.
Missing corners are the absence of wood at the corners of a board. This defect is usually only found on low-quality wood. Sometimes you can hide this defect by simply turning the board over.
Wood boards that are bent from end to end are known as “bending” or “crowning”. This can occur if the wood has dried unevenly or if there are tree pits around the edges of the boards. You can cut the boards and replace them with straighter, thinner boards. If you are cutting the outside of pressure-treated deck planks, be sure to treat the edges or ends with an approved chemical treatment first.
Some boards will bend along the grain line, but not across it. This is known as curvature. If the board is laid on a flat surface, both ends of the board will be in the air. This defect can occur if the wood dries with uneven airflow. Bowed planks are difficult to cut due to the high forces inside the plank, and breaking the plank can be dangerous. When you want to make a crosscut to it, the bow should be facing up.
When a board bends in a “U” shape from edge to edge, this is “cupping”. One often finds this on boards cut close to the pit. Planned boards can be made from boards cut into pieces. If you try to force a curved board into the plane, it will probably split.
A board is said to be “twisted” if it bends in more than one direction and does not stay in a straight line. One corner does not always line up with the other corners. This usually occurs when the wood grain is not straight along the edges.
Wood knots are wood defects caused by tree branches. For the purpose of grading wood, we group knots into groups based on their size, shape and strength, or how well they are held in place. Most knots are ugly; they weaken the board or are used as a starting point for inspection. The higher the quality of the wood, the fewer knots there are.
Wood and deck boards develop these defects because the lumber is stressed during sawing and trimming.
When a depressed board is manually flattened between the rollers’ planes, this is a Roller Check. light roller checks are up to 2 feet long, medium roller checks are 2 to 4 feet long, and heavy roller checks are 4 feet or more.
Skip” is the rough surface left wherever the planer has planned. This occurs when the board is too thin for the planer knife to reach and smooth the entire surface.
Machine Burn is the darkening of wood due to excessive temperatures, usually due to dull knives or blades. In most cases, this defect can be eliminated by sanding.
The first thing you need to do to avoid using defective wood is to choose high-quality wood. The next thing you need to do is figure out what problems you’ve found and how they will affect the look and function of the deck. After a period of time, you’ll soon learn which defects matter and which don’t.
If you don’t want to spend too much time inspecting the wood, you can opt for composite decking material. Composite decking board is a great alternative to traditional wood, and it doesn’t have those common wood defects.
Composite decking boards are made from high-quality materials and strictly controlled processes. Therefore, there are no natural or machine-made defects like wood. They can also be cut and joined like wood. Maintaining composite decking boards takes much less time and money than wood decks. While regular wood decking lasts between 10-15 years, composite decking lasts between 25-30 years.
Can You Put Composite Decking Over Existing Wood Deck?
How Much Does a 20 x 20 Composite Decking Cost in 2026?
What Is The Best Decking Material For Full Sun?
Why Does Composite Decking Warp and How to Fix It？
Can You Just Replace Deck Boards with Composite?
How to Building a Pool Deck Around an Above Ground Pool
How To Finish Off Composite Decking Edges?
Can Fire Pits Be Used on Composite Decking?
Composite Fencing for Coastal and Saltwater Environments
What You Need to Know About Deck Ideas
