How to clean mold, mildew and algae off your deck

Here in BC’s spectacular Lower Mainland, with all the wet weather that we get to enjoy, a common problem is this green algae that seems to build up in no time on the surface of decks. This is especially prevalent on wood decks, where it can build up in a matter of weeks, and is most common in shaded areas.

There’s no way to stop this algae from building up. It’s a nuisance and can be dangerous because it can create slippery conditions. Don’t be fooled by products that claim they will keep this from coming back, because such products don’t exist unless you were to use something with a dangerous chemical compound that would not be environmentally healthy. Keep in mind that piled-up leaves or other elements that may be on your deck will lock in moisture and create an environment where algae can flourish.

The good news is that cleaning this off is very easy.

You can get environmentally friendly cleaning products and spray or brush them on your desk for a fast and easy cleaning process. Clear your decking entirely of furnishings and pots and sweep the deck thoroughly with a stiff brush, making sure you get right into the corners where mold and algae have a tendency to build up.

Get environmentally friendly cleaning products and spray or brush them on your desk for fast and easy cleaning

Environmentally friendly cleaners will have a green label or designation to identify them from others. Industrial Paints and Plastics, with a few locations in this area, are a good, knowledgeable source of cleaning products. You can use a bristle brush to get into the harder to reach areas and that’s fine as long as the bristles are not made of something too stiff like steel so they don’t cause damage to the paint or stain surface.

All bleach is not created equal

One common environmentally friendly cleaning product is oxygen bleach. This is NOT the same as chlorine bleach, so don’t make the mistake of confusing the two! Chlorine bleach is dangerous and toxic and will destroy the finish and material of your deck. Oxygen bleach is a completely different compound that will not take the color out of your wood decking, your vinyl siding, your painted surfaces, or your roof. Typically, oxygen bleach is a powder that gets mixed with water. Once mixed, all you get is more water, oxygen ions that do the cleaning and some harmless organic soda ash. Not all oxygen bleaches are the same. Some are completely organic, while others contain fragrances, dyes, color crystals, and excessive fillers. Always go for completely organic.

Dissolve the powder in warm water, pour it into one of those garden hand-pump sprayers and squirt it on your algae-coated surfaces. Let it soak for about ten minutes, then use a scrub brush to remove the green algae. After rinsing with a garden hose, the surfaces should look brand new again.

Pressure washing not recommended

You should never pressure wash a wood deck because the power washing affects the painted or stained surface making it rough. It can easily peel it off, leaving exposed wood underneath which will then rot without immediate attention. Any damage to the protective paint or stain would force you to sand and refinish your deck which would cost you much more time and money.

Composite decks are safe for pressure washing because they are sealed and therefore relatively unaffected by the blast from the pressure washer. However, we still recommend that you use a mild eco-friendly cleaning solution and just apply it with a bristle brush to remove the algae, moss or mildew.

Composite decks are mostly maintenance-free

Composite decks enjoy a huge benefit when it comes to mold, mildew and algae because the compressed recycled synthetic material they’re made from means that these things don’t get below the surface of the deck. With wooden decks, they actually do embed themselves right into the fibers of the wood, so you need to deal with them quickly before it gets too deep into the grain of the wood.

With wooden decks, you may need to repaint or stain your deck on a regular basis, depending on where you’re located and which direction your deck faces. West and North-facing areas are most commonly affected because they spend so much time in the shade. The problem is less common on south-facing surfaces. On the North Shore, which tends to be more moist than Tsawwassen or White Rock, you may have to apply new paint or stain every year. In other places you may only need to do so every two years. Composite decks require very little maintenance, and even enjoy a limited 25-year residential warranty.

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