Wood Facts All unprotected wood exposed to exterior weathering is susceptible to erosion and biological attack. This natural weathering process results in wood changing its appearance from the beauty of new wood to various shades of gray and eventually to black. Left unprotected, new wood's durability, beauty and natural coloration is under constant attack. The enemies of your exterior wood surfaces are: sun, water, decay.
Photo Degradation by Ultraviolet Light - Sunlight. Solar radiation is the most damaging component of the outdoor environment affecting every exposed surface. The first change you will notice in your exterior wood will be the damage inflicted by sunlight. This will be seen by an initial color change from its beautiful golden, orange-brown color to gray. This color change is actually the decomposition of lignin (nature's glue for holding wood cells together); as it progresses the wood color darkens. (UV) rays bleach the wood fibers and break down the cell structure, helping to turn the wood GRAY.
SPLITTING OF WOOD, DECAY, ROT
Leaching - Swelling/Shrinking due to Water Absorption by the Wood. Sun and rain cycles cause moisture fluctuations in the wood. The shrinking and swelling stresses the wood causing checks and splits to develop. Hydrolysis (as in acid rain attack) is also a contributor to this degradation of your wood. Water is one of wood's worst enemies. Whether in the form of vapor or liquid, water can cause SHRINKING and SWELLING, which can lead to DIMENSIONAL CHANGES of the wood and DEGRADATION of the finish. Water causes DECAY and ROT of the wood and EARLY FAILURE of sealers, stains and other finishes. Water also SHARPLY ACCELERATES the weathering of unprotected wood exposed outdoors.
FUNGI, MOLD, MILDEW. ALGAE
Decay Promoting Microorganisms - Fungi, Mold and Mildew. Wood's natural defenders leach out in a relatively short time and allow colonization by wood-inhabiting fungi. Once established, and aided by favorable climatic conditions, these microorganisms can have a rapid, devastating effect causing your wood to become soft, stringy, pitted, cracked or even to crumble. Damp wood is a natural food source for mold, mildew, algae and fungus. This generally causes a black, green or gray discoloration on the surface. Many molds and mildews cause severe respiratory problems in humans.
YOUNGER TREES VS OLDER TREES
Depletion of Old Growth Timber. Another important consideration is that the majority of today's cedar and redwood lumber is being processed from younger, less decay resistant trees. These young redwood and cedars harvested today may need protection earlier than the premium hart woods that were once widely available. These factors, coupled with an increased awareness of various environmental issues in recent years to protect what remains of our old growth timber, are further reducing the supply of high quality wood. With all of these factors, (sunlight, water and fungi, attacking your untreated exterior wood ) you will soon notice your wood becoming "spongy", boards on fences begin to warp, split, and crack, and in severe exposures; wood rot becomes evident.
WOOD IS ORGANIC
Wood is Organic! Anything derived from a living or once-living organism is organic. Organic materials have many different qualities and uses. However, all organic materials have a common trait that sets them apart from other materials: they naturally decompose. Decomposition of organic material is inevitable. It is nature's way of recycling organic matter.
"The problem of decomposition (rotting) can be avoided or attenuated through knowledge about the factors that affect wood. If wood structures are given proper care initially and maintained properly, they can be functional and structurally sound, as well as aesthetically pleasing, for decades." U.S. Forestry Service