Wood Decay and The Importance of Wood Stain

By Steve Getsiv, 10/16/19

Tired Deck

Does your deck or picnic table look cracked or weathered? What causes these problems, and more importantly, what can you do about these problems? Keeping your deck beautiful and functional all year long can take work. Several different factors can cause decay and degradation in wood, and understanding these factors can help you maintain your deck beautifully.

Common Factors Causing Wood Decay


Moisture, or the lack thereof, causes wood to change its dimensions. There are two very specific conditions involving moisture that affect the size and shape of the wood.

  1. 1. When wood is completely deprived of moisture it begins to shrink.
  2. 2. When wood is completely soaked, wood begins to swell.

All wood is prone to these problems, but the amount it shrinks or swells, depends on the species of wood.

Results of fungi rot


The presence of fungi or rot can cause degradation to the cells of the wood. The cellular scan is an extreme case located in the ancient tomb of "King Midas", approximately 700 B.C. The image to the left is healthy wood, and the image to the right is wood that has been destroyed by fungi.

There are three major kinds of fungi that can destroy the wood on your deck:

  • Brown Rot
  • White Rot
  • Soft Rot

Here's a quick guide to identifying the type of rot you may be seeing on your exterior wood deck, wood fence or exterior wood furniture.

Brown Rot

Oak with brown rot

Brown rot is more likely to affect soft woods, such as cedar and pine. If brown rot is present the color of the wood will darken and the wood will begin to crack. The wood could also exhibit a dry and powdery texture, which is often mistaken for dry rot.

White Rot

White Rot

White rot is prevalent in hardwoods, such as mahogany and oak. White rot deteriorates wood at a slower pace than brown rot. The signs of white rot are harder to detect at an early stage. If you notice pieces of your deck that appear white or bleached, it may be suffering from white rot. Without proper care, white rot can eventually cause your wood to become soft and spongy and appear like soft rot

Soft Rot

soft rot

The last major type of wood degrading fungi is soft rot. If you live in an area that often experiences moist conditions, your deck may suffer from soft rot. Soft rot often causes wood to change color and soften to a spongy texture, hence the name.

While all three types affect the appearance of your deck, the problems they create go far beyond the surface. If left untreated, fungi can decrease the strength of your wood, damaging the structural integrity of your deck. Once the fungi have infiltrated the wood, your deck may become unsafe.

Weathering or Sun Exposure

Nova Blog Photo

When wood repeatedly goes from wet to dry, experiences high to low temperatures, or is over exposed to direct sunlight, it may begin to weather. When weathering occurs, the color, texture, and overall structure of your deck may be affected. These conditions may result in discoloration, cracking or splitting of your deck. Weather is an uncontrollable variable and will inevitably deteriorate wood over time when left unfinished.

Solutions, Preventions, and Wood Stains

Exoshield on table

The conditions discussed are all-natural occurrences, but that doesn't mean we can't do our best to prevent them from happening. The best way to prevent or prolong wood decay is applying a high-quality exterior stain. Wood stains contain active ingredients that protect the wood from common elements, thus prolonging wood decay. Most wood stains include additives that make the application process easier and improve the overall finish. Key additives for wood protection are UV blockers, pigments, resins, oils, and sometimes a fungicide.

Pigments and UV blockers act as sunscreen for wood, shielding the wood from UV rays, which will slowly turn the decking gray if left unfinished. Resins and oils dry and harden within the wood and are used to protect wood from moisture. The type of oil a product uses can greatly change how well a product works. For instance, Linseed Oil is highly susceptible to mildew and fungus and can often cause boards to turn black over time; whereas polymerized Tung Oil is naturally resilient to mildew and fungus.

Regularly applying a high-quality wood stain, such as ExoShield, will improve the safety, appearance and longevity of any outdoor wood deck or product. This renews the UV protection, fungicide properties, and water repellency of your deck, and beautifies the wood. The timeframe between applications depends on your local weather conditions, but inspecting on a regular basis, for example every spring, with application at that time as needed is a great plan to increase the longevity of your wood.

For an example on how to do a maintenance coat of ExoShield please see our YouTube channel here or call us at 503-419-6407!

By Steve Getsiv, 10/16/19

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