Mildew and algae can grow on both horizontal and vertical exterior surfaces. They can grow so slowly that you may not be aware of their presence until they become very visible by discoloring the surface, or when a walking surface becomes slippery, especially when the surface is wet.
Mildew is typically black or gray in color, and algae has a greenish appearance. They are usually found on surfaces that do not receive much direct sunlight and therefore have a tendency to remain damp. If left on a surface, the surface can eventually become stained by these organisms.
This outdoor surface has both mildew and algae growth. This growth can discolor the surface over time and can create a slippery surface. Notice the lighter square markings from an object that was removed from the area. Many times the graying of a surface is harder to notice than the greenish cast of the algae.
It’s important to keep outdoor walking areas clean to help keep surfaces from getting slippery. Dirt, leaves, and standing water are a few things that can provide food sources for mildew and algae. Simple, routine maintenance, like removing leaf clutter, debris, and splatters from the grill, and sweeping dirt residue from walking areas can help remove certain food sources, and help to provide a safer walking surface.
Cleaning Products for Outdoors
There are several good products for cleaning mildew/mold and algae from outdoor walking areas. Ultra concentrated oxygen bleach provides effective cleaning, and removes stains as well. You can read here on how to clean pavers with oxygen bleach. Mildewcide cleaners will kill mold and mildew (mildewcides do not get rid of algae, though). Defy and Zinsser both manufacture quality outdoor cleaning products, and we listed a few below.
Check out these cleaning products, and their complete lines of cleaning products, to find a product that will suit your particular outdoor cleaning needs. Many of these cleaning products are safe for a multitude of outdoor surfaces, and plants. Before purchasing any cleaning product, read the label to check if it is the correct product for you.
- Ultra concentrated oxygem bleach
- Defy Wood Cleaner
- Zinsser JOMAX Mildewcide Concentrate
- Zinsser JOMAX Multi-Purpose Exterior Cleaner & Brightener
Always follow the manufacturer’s directions for their product.
New Construction Projects
If you are building a walk, deck, patio, or other outdoor area, employing proper construction methods can help surfaces dry faster. These include, but are not limited to, sloping the surface to have positive drainage, and using a 1/8” minimum gap between porch and deck boards to help with water drainage.
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