Wood Defects: What’s Normal and What’s a Problem?

Part of what makes wood so beautiful is it’s unique grain and the character that comes from it being a natural, living material. But because it spent decades growing in a forest, real wood–and the furniture made from it–will never be perfect. For example, solid wood furniture will have some color variation and marks and it will grow and shrink slightly with changes in the environment. But that doesn’t mean every imperfection is acceptable. Sometimes there are flaws that just aren’t okay. So what’s considered normal and what’s considered a defect? Let us break it down for you.

Visual Characteristics of Solid Wood Furniture

• Color Variation – Boards of the same species will look a little different, both from tree to tree and also within the same tree. A little science to explain why: The outer part of the trunk is called sapwood, and it’s made up of the active cells that carry water through the tree. This sapwood tends to be lighter in color then the inner part of the trunk. (It’s even someone’s job to color match boards so your furniture looks as good as it can–read about that here!).
• Color Changes – After you get your wood furniture home, it will change color as it is exposed to light. Cherry will darken, walnut will lighten, and maple will turn honey. If you purchase furniture with the natural wood color showing (not stained), you can expect it to look different in about six months time. You can read more about the specifics of each wood species here.
• Grain Variation – The grain is caused by the growth rings of the tree, which result in the swirly lines you see running through the surface of wood furniture. Certain species of wood have consistent grain visibility – ash shows a pronounced grain while maple’s is less so – but within a species, the grain on each board will look different.
• Knots – The spot where a branch hits the trunk can cause circular patterns called knots. Some species like pine have a lot of knots–it’s actually a characteristic of that wood. Larger knots are removed from boards before they’re made into furniture, but smaller knots (sometimes called pin knots) are part of the wood’s character.
• Pitch Pockets – These small marks are caused by insects that injure the trunk cells, resulting in gum spots. They show up as darker spots on lighter wood tones or, if the wood is stained dark, you will notice a difference in sheen on those spots.
• Mineral Streaks – These are darker lines that follow the wood grain. They’re caused by minerals that the tree extracts from the soil while it grows.

All of these features are part of the beautiful character of wood, and are to be expected in your solid wood furniture. If you want to minimize visual variation, choose a dark stain that will hide the darker marks and make the color changes that occur over time less obvious.

Dimensional Characteristics of Solid Wood Furniture

Wood remains dynamic even after it’s been cut down and it constantly adapts to its environment. Changes in environmental moisture will cause the wood to expand (this happens when there’s more moisture in the air) or shrink (caused by less moisture in the air). This movement may cause small-but-noticeable structural changes.

Furniture moves in a very specific way: It expands only in width (a board won’t grow longer) and absorbs more moisture in the ends. You may notice this effect most on dining tables made from large panels. Some things you might see are:

• Belly – A slight dip (only about 1/32″ or so) in the middle of the table. This is caused from the ends expanding more than the middle and is not a defect.
• Gap – If you have an extension table with a break in the middle, you may notice a gap in the middle of the opening that separates the two sides. This is not a defect.
• Warping – When one surface takes in more moisture then another, the wood will drastically curve or bend. If you notice a curve that runs the whole length of the table, this is warping. It is very common, but can avoided with good manufacturing practices. There should be no more than six inches of unsupported wood surface (additional pieces of wood should be secured to the underside of furniture panels).
• Leaf Size Differences – If the leaves of a table are stored somewhere else in your house, you may notice a small difference in width when you insert them into your table. If you have breadboard ends (extension leaves that are added to the ends of a table), they may be a touch smaller then the table end.
• Cracks – If a piece of wood goes to a home in a a dramatically dryer environment than it was built, it may crack. This should never happen if proper care was taken to the drying of the wood. You may be able to live with small, hairline cracks, but larger cracks are a major problem. Imported furniture is more susceptible to this because it comes from tropical locations where humidity is high.
• Gaps in Construction – Dressers and cabinets are made by building a large box, then adding in the drawers and doors. You may notice some gaps where the different wood surfaces are joined together or around the door and drawer fronts.
• Glue Lines – Large wood panels are made by gluing wood boards together (read more about that here), this is typically a pretty sturdy joint, and shouldn’t show any cracks.
  

What Quality Manufacturers Do Right

It’s impossible to stop wood from moving at all, but there are some steps manufacturers can take to minimize the changes:

1. Proper Drying – After harvesting (read more about that here) and milling the trees into boards, lumber is kiln dried to 6-8% moisture content, down from 40% when the wood is alive. Most living areas have a moisture range between 4% and 11%, so wood that is close to that moisture level should acclimate well.
2. Moisture Check – Good manufacturers will check the moisture content before construction to ensure it is still in a good range.
3. Finishing – It is important to finish all sides of the wood to reduce moisture gain or loss.
4. Supports – As mentioned above, there should be no more than six inches of unsupported wood surface.
5. American Made – Purchasing from American manufacturers helps with several of these issues:
   • Wood does not come from drastically different environments
   • Wood is dried to appropriate moisture levels
   • Less cost cutting in construction, so you are more likely to find a piece that is finished on all sides and has the proper support

The living nature of wood brings a beautiful, organic element to your home. The variations in the look of wood should be admired for their unique appearance and not labeled as a defect. While major structural changes in wood should be a concern, some small fluctuation is normal and is not a cause for alarm.