Why Mildew Is So Common on Covington Wood Siding
If you own a home with wood siding in Covington, you already know that mildew is more than an occasional nuisance. Big Easy Siding works with homeowners across the Northshore who deal with mildew buildup every year, and the reason comes down to where Covington sits and how the climate works.
Covington and the broader St. Tammany Parish sit under one of the densest tree canopies in southeastern Louisiana. Live oaks, cypress, and pine create heavy shade that keeps moisture on exterior surfaces for longer stretches of the day. Combine that shade with Louisiana’s average relative humidity of 75 to 90 percent during the warmer months, and you have ideal conditions for mildew to take hold on wood siding.
Older homes on the Northshore are especially vulnerable. Many were built with natural wood clapboard or board siding that absorbs moisture more readily than modern composite materials. North-facing walls, areas beneath eaves, and sections of siding close to landscaping tend to develop mildew first because those surfaces stay damp the longest.
Mold vs. Mildew: How to Tell the Difference
Before you start cleaning, it helps to know exactly what you are dealing with. Mold and mildew are both fungi that thrive in damp environments, but they look different and carry different risks.
Appearance
Mildew typically appears as flat, powdery patches that are white, gray, or light brown. Mold tends to be darker, showing up as fuzzy or slimy spots that are green, black, or deep brown. On wood siding, mildew often looks like a light dusting or film, while mold can appear as raised, irregular patches that penetrate deeper into the wood grain.
Health Concerns
Mildew is generally a surface-level issue and is not considered harmful to most people. Mold, on the other hand, can release spores that trigger respiratory problems, allergic reactions, and other health issues. If you see widespread dark discoloration or fuzzy growth on your siding, it is worth having the area tested before you begin cleaning.
Structural Impact
Left untreated, mildew can lead to staining and surface degradation. Mold is more aggressive and can cause wood rot, weakening the structural integrity of your siding over time. In Covington’s humid climate, what starts as surface mildew can progress to mold if the underlying moisture problem is not addressed.
Supplies You Need Before Getting Started
Gather everything before you begin so you can work through the process without interruption. Here is what you will need:
- Rubber gloves, safety goggles, and a dust mask to protect yourself from cleaning solutions and airborne spores
- A garden hose with a spray nozzle for rinsing
- A soft-bristle brush or sponge for scrubbing (avoid wire brushes on wood siding, as they can gouge the surface)
- A pump sprayer or spray bottle for applying your cleaning solution
- Drop cloths or plastic sheeting to cover nearby plants and landscaping
- Your chosen cleaning solution (see the section below for options)
- A bucket for mixing
Step-by-Step Mildew Removal for Wood Siding
Follow these steps to safely remove mildew from your Covington home’s wood siding without causing damage to the wood itself.
1. Protect Surrounding Areas
Cover plants, shrubs, and flower beds near the siding with drop cloths or plastic sheeting. Cleaning solutions, even mild ones, can damage foliage if left in contact too long. Move outdoor furniture, grills, and decorations away from the work area.
2. Put on Protective Gear
Wear rubber gloves, safety goggles, and a dust mask. Scrubbing mildew can release spores into the air, and cleaning solutions can irritate skin and eyes. This is especially important if you are working on a section of siding where the growth has been building up over a full Louisiana summer.
3. Pre-Rinse the Siding
Use a garden hose to rinse the affected area with clean water. This removes loose dirt, cobwebs, and debris so the cleaning solution can make direct contact with the mildew. Start at the top and work downward to avoid pushing dirty water into clean areas.
4. Apply the Cleaning Solution
Using a pump sprayer or spray bottle, apply your cleaning solution to the mildewed sections. Work in manageable sections of roughly four to six feet at a time. Let the solution sit on the surface for 10 to 15 minutes so it can break down the mildew. Do not allow the solution to dry on the wood.
5. Scrub the Surface
After the solution has had time to work, scrub the area with a soft-bristle brush. Use firm, even strokes that follow the grain of the wood. For stubborn deposits, reapply the cleaning solution and let it sit for another 10 minutes before scrubbing again. Avoid using metal brushes or abrasive pads, which can scratch and damage the wood surface.
6. Rinse Thoroughly
Rinse the entire section with clean water from your garden hose. Make sure all cleaning solution residue is removed, as leftover product can discolor the wood or attract new dirt. Again, work from top to bottom.
7. Allow the Siding to Dry Completely
Let the siding air dry before applying any sealer, stain, or paint. In Covington’s humid conditions, this may take one to two full days of dry weather. Do not seal or paint over damp wood, as trapped moisture will create the same mildew problem all over again.
Choosing the Right Cleaning Solution
The cleaning solution you use matters. Different options work better depending on the severity of the mildew and the condition of your wood siding.
Oxygen Bleach (Sodium Percarbonate)
Oxygen bleach is one of the safest and most effective options for wood siding. It breaks down into water and oxygen after use, making it gentler on plants and the environment compared to chlorine bleach. Mix according to the product label, typically one cup of powder per gallon of warm water. Oxygen bleach penetrates porous wood surfaces to kill mildew at the root, which helps prevent quick regrowth.
White Vinegar Solution
A solution of one part white vinegar to four parts water works well for light to moderate mildew. Vinegar is a natural acid that kills most mildew species on contact. It is safe for most painted and stained surfaces, though you should test a small, hidden area first. Vinegar is a good choice for homeowners who want to avoid chemical products.
Chlorine Bleach Solution
A mixture of one cup chlorine bleach per gallon of water is effective for severe mildew. However, chlorine bleach can strip color from stained wood and may damage plants if it runs off into landscaping. If you use chlorine bleach, keep the affected area wet and rinse thoroughly after scrubbing. Cover all nearby vegetation before applying.
Commercial Mildew Cleaners
Several commercial products are formulated specifically for mildew removal on wood surfaces. Look for products labeled safe for wood siding and follow the manufacturer’s instructions for dilution and contact time. Many of these products contain surfactants that help the solution cling to vertical surfaces longer.
Pressure Washing Wood Siding: When It Helps and When It Hurts
Pressure washing can speed up the mildew removal process, but it carries real risks when used on wood siding. High-pressure water can splinter wood fibers, force water behind the siding and into wall cavities, and strip paint or stain from the surface.
If you decide to use a pressure washer, follow these guidelines:
- Keep the pressure below 1,500 PSI. Higher settings can damage softwood siding like pine and cedar.
- Use a wide-angle tip (25 or 40 degre