February 2

Protecting Your Exterior Wood from Mold, Mildew, and Lichens


Wood is an excellent building material due to its durability, versatility, and rustic charm, but it’s also susceptible to damage and invasion by miniature culprits; mold, mildew, and lichens. Though they might seem like dainty microorganisms, left unchecked, they can cause significant damage and discoloration to your exterior wooden structures. Across this three-part article, we will explore these microscopic perpetrators, delving into their similarities and differences, the impact they can have on exterior wood, and how you can protect and restore your wooden surfaces effectively. We aim to provide well-researched, in-depth, and user-friendly knowledge that will help you preserve the integrity of your exterior wooden spaces. Join us, as we unravel this small yet complex world of fungi and their impact on your exterior wood structures.

What is Mold?
Mold is a familiar sight to most of us and typically takes center stage in the “war on yuck”. Mold is a type of fungus which feeds on organic matter in the presence of moisture. Billions of tiny mold spores fill the air around us. These microscopic adventurers float about until they find a damp, neglected corner in our environments to call home. Once settled, they start to reproduce and form colonies, creating those unsightly, fuzzy patches in varying colors – blue, green, black, or even white.
Mold isn’t just an aesthetic issue. Sure, it’s definitely not a look you’d want for your home decor but there’s more to it. When growing out of control indoors, mold can damage household materials, as well as pose health risks. While some folks might suffer nothing worse than a minor allergic reaction, for others, exposure can lead to more serious health problems.
If there’s a superstar in the world of fungi infamy, it’s black mold. Black mold, or ‘Stachybotrys’, excretes toxic compounds that can trigger severe reactions, even causing chronic diseases under extended exposure. However, before you hit the panic button on spotting black mold, remember – all molds should be dealt with promptly, regardless of their color.
What is Mildew?
Unlike mold, mildew restricts its scenic outbursts to surfaces only without penetrating beneath. You’re likely to spot these unsightly patches in wet areas, more commonly outdoors. Mildew spots often appear as a thin, superficial growth with a powdery or downy texture. This fungi-cousin shows up in discolorations of white, yellow, or grey.
Mildew might be more polite than mold, sticking only to the surface it claims, but it’s not to be ignored. Mildew-covered surfaces are more than just an eyesore – if emitted spores are inhaled, they can cause headaches and respiratory problems. The risk is especially high for individuals with allergies or asthma.
The good news though, mildew’s somewhat more superficial lifestyle makes it easier to remove than its more invasive cousin, mold. Simply scrubbing the surface with a mildew-specific cleaning agent or a vinegar solution can effectively evict this unwelcome guest.
What are Lichens?
Lichens are the superheroes of the mold world. They’re a unique organism created by an alliance between fungus and algae. The fungus provides the structure, (the ‘body’ if you will), and the algae produce food using photosynthesis. Lichens are often found in cool shapes and colors, clinging to almost anything – rocks, soil, tree bark, and even weathered wood.
Lichens look enchanting, transforming plain surfaces into nature’s art. Don’t be fooled though; they can be troublesome. They’re stubborn, slow-growing, and tough to remove. When lichens decide to settle on your exterior wood structures—like that beautiful rustic barn door or the classic outdoor bench—they can cause discoloration and damage.
The worst part? Lichens refuse to die easily. They go dormant under unfavorable conditions only to revive and thrive when the situation improves. So, ‘out of sight, out of mind’ just wouldn’t work when dealing with this crafty duo of fungus and algae.
On the surface, mold, mildew, and lichens might look like the fungal cousins nobody wants at their party. But it’s intriguing how they share some fundamental qualities despite their differences. Enter any damp, shady corner, and you might meet at least one of these funky trio. They’re survivors, thriving in unnecessary nutritious conditions and can go dormant when the living gets tough.
They share common spatial choices like damp walls, humid bathrooms, or soggy old wood in the backyard. They are nature’s multi-dimensional artists, blossoming into fuzzy growths, powdery patches, or vibrant pavements. But don’t let their artistic flourishes fool you – left to their devices, they can cause a surprising amount of damage.
While they might be part of the same fungal family tree, mold, mildew, and lichens have their own unique identities too. Mold is like the deep seas, fascinating in diversity and color, but potentially catastrophic when uncontrolled. Mildew, on the other hand, is more of a surface-dweller, setting up shop on your possessions but limiting its destruction to the superficial. Lichens betray their dual nature in their resilience and wide-ranging habitats across rocks and woods.
They differ not just in their flavors of destruction but also in the environments they choose to proliferate. Damp basements and food leftovers are like mini ‘mold heavens’, while mildew finds its paradise on surfaces like the outdoor decking that’s weathered many a rainstorm. Lichens, on the other hand, are the obstinate hermits, grabbing onto the loneliest spots and turning anything drab into a vibrant slice of nature.
External factors that encourage their growth
Mold, mildew, and lichens – they all love a stage that’s humid, devoid of direct sunlight, and slightly warm. Moreover, they are lovers of organic material whether that be the paint on your exterior walls or the rough-finished wood of your patio furniture.
Spores of mold and mildew can sail on a fresh breeze, ride sneakily on a favorite pet, or cling secretly to the clothes just thrown in the laundry basket. Their preferred plot for the next ‘fungus fest’ is usually the spot where moisture settles for long. A leaking pipe in the corner or a pile of autumn leaves on your deck could be the perfect location for the next ‘fungus bonanza’. So, the best preventive defense is an offense – don’t let moisture linger and give regular cleaning a chance.
Part 2: Impact of Mold, Mildew, and Lichens on Exterior Wood
How Mold Affects Exterior Wood
Mold is an invasive organism. Once it settles in, it starts breaking down the organic material in wood. Over time, what was once a sturdy structure can become soft, crumbly, and weak. On top of this, molds will often discolor the wood. You may notice black, green, or blue tints cropping up on your structures.
But the problems aren’t just aesthetic. Mold spores, once airborne, can be inhaled. In the best-case scenario, they cause allergies in sensitive individuals. Worst case, they can lead to serious respiratory problems. People with existing respiratory issues can see their conditions exacerbated by the presence of mold.
Dealing with a mold issue is more than just cleaning up the visible bits. It’s vital to address the moisture issues that allowed the mold to take hold in the first place. Permanent solutions may involve structural changes to ensure water can’t accumulate on your wooden surfaces.
How Mildew Affects Exterior Wood
Mildew, like mold, can discolor and damage your wood. But because it’s largely a surface dweller, the effects are less severe. Over time, your beautiful wood can develop a gray and dirty look thanks to a mildew infestation. And that’s not all. Because it prefers the outdoors, it can wreak havoc on your yard structures.
Mildew spores can cause a series of health issues. People with allergies or respiratory conditions can be especially sensitive. Coming into contact with mildew or breathing in its spores can lead to coughing, headaches, and sore throats.
Remember, cleaning up a mildew infestation requires dealing with the underlying moisture problem. Work on improving air circulation in the area, and consider investing in a dehumidifier. Trimming back foliage can also help expose affected surfaces to more sunlight, thereby reducing moisture levels.
Impact of Lichens on Exterior Wood
Although it’s not as harmful as mold or mildew, lichen can still hurt your exterior wood surfaces. Over extended periods, it can gouge out small notches and grooves in the wood. These small abrasions can catch and hold water leading to rot and other water-related damages.
Lichens can be particularly tough to remove. Unlike mold and mildew, they can’t be just wiped or washed away. Once established, lichens intertwine their fungal and algal components, rooting themselves into the very structure of the wood.
Eradicating lichen requires a multi-step approach. You’ll have to remove the organism, clean the surface, and protect the wood against future infestations. Just like mold and mildew, successful control of lichen depends on modifying the environment to make it less hospitable. This could mean increasing sunlight exposure, reducing dampness, or improving ventilation
Part 3: Prevention, Treatment, and Maintenance for Healthy Wood
Prevention Techniques
An ounce of prevention is worth a pound of cure, especially when dealing with stubborn fungi like mold, mildew, and lichens. Regular maintenance is vital in keeping exterior wood structures healthy. Start with selecting appropriate wood for outdoor use. Certain varieties have natural immunization to fungal growth, and using these can give your exterior structures a fighting chance.
Proper sealing is paramount. Applying a high-quality sealant provides a tough layer of defense against mold, mildew, and lichens. Regular re-application in intervals based on manufacturers’ instructions can keep fungal fiends at bay.
Last but not least is the practice of good outdoor housekeeping. Ensure that your wood structures are not waterlogged or left damp. Prune trees and shrubs to enhance sunlight exposure, making your garden a less enticing breeding ground for these fungi. Remember, controlling the moisture and sunlight exposure is key to preventing fungi from colonizing your exterior wood.
Effective Treatment Methods
When preventative measures fall short, and you find yourself notwithstanding a fungal invasion, swift action can mitigate damage. Start by identifying and fixing any issues contributing to the excess moisture. Then, reach for a suitable fungus-specific cleaner – there are many effective and environmentally-friendly options available in the market.
For immediate mold and mildew issues, scrub the area with a soft brush and an appropriate cleaner. Rinse it thoroughly and let the wood dry completely. In cases of deeply rooted mold or extensive lichen growth, considered hiring professionals. They have both experience and tools suited to handle large-scale or difficult infestations.
Maintenance Post Treatment
Your work isn’t over once you’ve treated your wood. Regular maintenance is vital to keep it healthy and beautiful. Inspect surfaces periodically and clean them as necessary. Repaint and reseal surfaces regularly to keep them well-protected. Remember to keep potential moisture sources in check. Correct landscaping issues that may lead to water accumulation.
Pay attention to your wood as the seasons change. Different weather conditions can create a hospitable environment for different fungi species. Depending on your site, you might need to adjust your maintenance routine with changing seasons.
With careful and consistent care, your exterior wood structures can remain free from mold, mildew, and lichens. Healthy wood not only looks fantastic, but it can also be a source of pride for your home or property.

Pro-Tip 1: Proper ventilation aids in reducing the likelihood of mold, mildew, and lichens taking over. Ensure your outdoor wooden structures are placed where there is enough air flow.
Pro-Tip 2: Regularly clean your wooden surfaces. Use soft brushes to scrub off dirt and debris. It’s easier to prevent these organisms than to eradicate them once they’ve settled in.

Pro-Tip 3: Monitor the health of your woods. Inspect your wooden structures regularly for the early signs of fungal growth. Early detection and treatment can prevent further damages.
Pro-Tip 4: Seal your wood properly. A good quality, water-repelling sealant can create an efficient barrier against moisture, a key cause of mold, mildew, and lichens.


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