Vinyl siding is a popular exterior cladding for many homes due to its durability, low maintenance, and customized appearance. However, vinyl siding can develop spots, stains, or discoloration over time from various causes. Identifying what is causing spots or stains on your vinyl siding will help determine the best way to remove them and prevent further damage.
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What causes spots on vinyl siding?
There are several common culprits that can lead to spots, stains, or discoloration on vinyl siding:
- Mold and mildew growth
- Dirt and dust accumulation
- Chalking of the vinyl surface
- Water spots and stains
- Tannin staining from nearby trees
- Oxidation or weathering of the vinyl
- Bird droppings or insect waste
- Smoke and exhaust stains
- Chemical reactions with cleaners or pesticides
Let’s look at each of these common causes in more detail:
Mold and Mildew
Mold and mildew growth results in black, green, or brown spots on vinyl siding. It thrives in damp, humid environments with poor air circulation. Shady or low-lying areas of your home’s exterior are prone to mold and mildew. Regular cleaning is required to remove and inhibit regrowth.
Dirt and Dust
Like any exterior surface, vinyl siding accumulates dirt, dust, and other particulate matter over time. This can lead to dark streaks or spots as the particles adhere and build up on the siding. Areas with high vehicle traffic, construction, emissions, or drought conditions tend to collect more dirt and require more frequent cleaning.
Chalking
Over time, the vinyl surface can start to break down from sun exposure in a process called “chalking.” The siding develops a chalky, powdery appearance and may turn a light gray color. Chalking is a natural weathering process but indicates the siding exterior is degrading.
Water Stains
Excess moisture draining down the exterior walls leaves behind mineral deposits, dirt streaks, and other contaminants. Hard water contains minerals that leave white, yellow, or brown stains on the siding. Water splashing up from the ground level can also stain.
Tannin Staining
Tannins are organic compounds produced by some trees, especially oaks, redwoods, and cedars. As rainfall washes over the leaves and branches, tannins leach into the water. The tannin-rich water then leaves behind rusty orange, brown, or black streaks on vinyl surfaces. Avoid planting tannin-leeching trees near vinyl siding.
Oxidation
When vinyl siding is exposed to sun and rain for many years, oxidation can occur. This causes fading, yellowing, and surface deterioration. Harsh weather, pollution, and other environmental factors accelerate oxidation. Older, weathered siding will need replacement.
Bird Droppings and Insects
Bird droppings contain uric acid that can etch or stain vinyl surfaces. Insect waste and secretions, such as from aphids or scale insects, can leave tiny yellowish or black dots on siding. Bird deterrents, prompt cleaning, and insect control can help minimize these issues.
Smoke and Exhaust
Smoke from grills, fireplaces, cars, and industries contains small particles that embed in and stain vinyl siding, especially in areas with poor air flow. Soot, grease, and exhaust can leave grayish-black streaks.
Chemical Reactions
Using abrasive cleaners, strong solvents, or commercial pesticide and herbicide products on your vinyl siding can damage the surface. These chemicals may react with the vinyl polymers, causing discoloration, etching, or accelerated weathering. Always read product labels thoroughly before applying to vinyl exteriors.
How to Clean and Remove Spots from Vinyl Siding
Cleaning vinyl siding regularly, at least once per year, can help minimize staining and keep your siding looking its best. Here are some tips for effectively removing common spots:
Start With a Gentle Wash
Begin by spraying down the vinyl siding with a regular garden hose. This will help loosen and rinse away any loose dirt and debris. Use a soft bristle brush to gently scrub the siding while washing.
Clean With Non-Abrasive Products
For most vinyl siding cleaning, a mild detergent and water solution is sufficient and non-damaging. Dish soaps and cleaners designated safe for vinyl work well. Use a soft sponge or cloth, avoid abrasive scrubbing, and rinse thoroughly.
Remove Mildew and Algae
For mold, mildew, and algae growth, use cleaners containing ingredients like chlorine bleach, hydrogen peroxide, or sodium hypochlorite designed specifically for vinyl siding. Rinse thoroughly and allow to fully dry.
Brighten with Oxygen Bleach
Non-chlorine oxygen bleach cleaners can help brighten dingy, oxidized siding and remove stains without damaging the vinyl. Apply with a soft brush and rinse completely.
Try Ammonia for Grease
For tough grease stains from grill smoke or vehicle exhaust, an ammonia-based cleaner can cut through and dissipate the oil. Rinse thoroughly afterward and always follow safety precautions when using ammonia products.
Remove Tannin Stains
Tannin stains can be difficult to remove from vinyl siding. A bleach-based cleaner designed for tannin removal may be required. Reposition downspouts and trim trees to prevent excess tannin exposure.
Scrub Off Bird Droppings
Use a stiff bristle brush and vinegar solution to scrub away dried-on bird droppings. Rinse thoroughly. Wipe up fresh droppings as soon as possible before the uric acid etches the siding.
Power Wash as Needed
For whole-house vinyl siding cleaning or extremely dirty siding, a pressure washer may be necessary. Use caution to avoid damaging the siding – do not exceed 1200 psi and keep the nozzle at least 12 inches away from the vinyl. Hire a professional for best results.
How to Prevent Spots on Vinyl Siding
To help keep vinyl siding clean and prevent spots between deep cleanings, consider these tips:
- Inspect siding regularly and address stains quickly before they set in
- Install downspout extensions to direct roof runoff water away from siding
- Avoid planting trees and shrubs too close to the house exterior
- Use drip irrigation near the foundation instead of sprinklers
- Keep lawn sprinklers aimed away from siding and reduce watering frequency
- Clean gutters and downspouts regularly to improve drainage
- Maintain good exterior air flow and ventilation
- Control nearby sources of smoke, exhaust, and overspray
- Deter birds and insects from nesting or gathering on the siding
- Quickly clean any grease spills from barbecuing near the house
- Consider vinyl cleaners and protectants to shield siding
When to Repaint or Replace Vinyl Siding
If vinyl siding becomes excessively chalky, faded, cracked, warped, or develops large holes and damage, repainting or full replacement may become necessary. Signs it may be time for siding replacement include:
- Flaking or peeling paint if previously repainted
- Buckling or loose siding panels
- Soft spots, cracks, or holes in the vinyl
- Missing or damaged sections of siding
- Extreme chalking and oxidation
- Warping or melting from heat damage
- Pervasive mold, mildew, or algae growth
Hire a reputable vinyl siding company to inspect your exterior and determine if your siding needs replacement or can be repaired and repainted. Spot replacement of damaged sections may be adequate in some cases.
Conclusion
Spots on vinyl siding can happen over time from mold, mildew, dirt accumulation, weathering, bird droppings, and other factors. Regular cleaning with non-abrasive cleaners can help remove many common stains and prevent further buildup. For heavy chalking, oxidation, or other serious damage, professional repainting or siding replacement may be required. Addressing any spots quickly when they appear and maintaining good exterior cleaning practices are the best ways to keep vinyl siding looking like new.
