Maintaining the Health of Your Wood-Shingle Roof


Throughout its life, a wood-shingle roof comes under attack from things such as sunlight, wind, rain, fungi, etc.  A roof covered in debris only complicates the problem.  Fortunately, a homeowner can do something about it.  Roofs can wear down in as little as ten years—but with simple maintenance, you can prolong the health of your wood-shingle roof for a few decades.  To do this, a you must understand what a roof is going through.

It All Starts with Sunlight…

An initial light-gray discoloration occurs within the first few months after a roof’s completion.  This discoloration happens because the sun’s light has worn through the outer layer of the wood shingles.  This discoloration comes quickly, but eventually the light-gray discoloration darkens and becomes a more graphite gray.  This darkening indicates that fungi are now colonizing your wood-shingle roof.

Here Comes the Rain…

Here is an important fact about wood: it rapidly attracts water to its surface to cause swelling, but when the wood later dries, it shrinks.  How wood handles water—this swelling and shrinking—causes stress upon itself.  This stress is what leads to the first cracks in a wood-shingle roof.  What’s more, if you live in a colder climate where the water absorbed by a roof freezes and then thaws, the situation is aggravated—cracks will form more rapidly.

The Cracking Begins…

Cracking follows a cycle.  The cracks that develop in wood-shingle roofs trap water in the wood, and fungi appreciate the moisture.  With the extra water, the fungi easily grow and continue to rot the wood shingles, which helps the cracking.  Overtime, the growing cracks take more moisture and more fungi deeper into the wood shingles, and then the process repeats itself.  The fungi continue to feed on the wood, causing further destruction.  Eventually, the cracks lead to warping.

Pile on the Debris…

Debris (think leaves and branches of trees) complicates the problem: it helps to trap larger amounts of moisture.  Now, with so much excess water, larger types of fungi like moss or lichen can grow, which they do around the edges and valleys of wood shingles.  These larger types of fungi proceed to rot a roof at an enhanced pace and drastically shorten the lifespan of your wood-shingle roof.

What You Can Do:  Clean!

At this point, we can say that trapped moisture is the most destructive element in the decaying of wood-shingle roofs.  The first remedy is straightforward: clean your roof of debris.  This can be done easily with a simple garden hose combined with careful sweeping using a broom.  An even more effective means would be to use a power-washer, which can both remove fallen leaves and smaller branches, but can also remove any moss or lichen—especially the moss and lichen in those tight areas between the individual shingles.

Do not pay attention only to the debris actually on your roof—the branches of nearby trees with their leaves can block out much of the daylight, which usually would help the drying process.  What is more—overhanging branches and leaves from nearby trees can scrape a wood-shingle rooftop, and the potential gouges left behind function similarly to cracks.

So Your Roof Is Clean…Now What?

There are a handful of chemical treatments that can be applied to a wood-shingle roof. Cleaning solutions can be prepared from basic household ingredients.  These solutions are often an easy means of removing dirt, light stains, and faint patches of moss or lichen. These solutions can be applied with a broom or brush then rinsed off afterwards with water.  An example of a homemade solution is a mixture of tri-sodium phosphate, laundry detergent, and bleach.

For more powerful stains, stronger bleaching solutions can be used.  A concentrated solution can be used straight from the bottle for the most stubborn stains, but in general a solution made up of a lower concentration of bleach results in a more consistent result in color.  This sort of treatment should be applied with small brushes or spray bottles made out of either plastic or stainless steel.  These solutions should be wiped off within thirty minutes.

Chemical solutions are recommended for the most unrelenting moss and lichen.  These solutions are toxic and should be handled carefully and are applied using water cans or even pump sprayers.  The most popular chemical solutions are zinc sulfate, copper sulfate, and zinc chloride.  Just watch out for your gutters: chemical solutions can corrode them.  Also, check common weed-killers—they often prove effective at killing moss and lichen.

Your Roof Is Looking Spotless…How to Keep It That Way

Certain chemical solutions can be applied to wood-shingles to extend their durability.  Referred to as wood preservatives, these chemicals hinder the growth of the various fungi.  In general, wood preservatives are more effective when applied earlier on in a roof’s lifespan: if a roof is simply too old and warped, then a wood preservative won’t do much; but if you regularly clean the debris from your roof and often apply a cleaning solution, then a wood preservative should be used as insurance during the time between cleaning spells.  Copper naphthenate, zinc naphthenate, and copper 8 quinolinolate are popular forms.

In Conclusion…

There are many things that wear away at a wood-shingle roof, but the necessary steps to maintain it are easy enough.  Trapped moisture is the most harmful ingredient: it causes the cracks and is needed by various fungi, moss, and lichens to grow and multiply.  Cleaning debris from your roof is essential to removing the majority of trapped moisture from a roof and can be accomplished by simple means—such as using a garden hose.  Also, there are various cleaning, bleach, and chemical solutions that help eradicate patches of moss or lichen, and there are wood preservatives that help to keep the invaders away.  The steps are easy, and they can add decades to the health of a wood-shingle roof.

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