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How To Clean A Retaining Wall with Wet & Forget

By Wet & Forget

A retaining wall’s humble existence belies its importance to most yards. Not only does it add functionality to sloped landscapes, but it also offers an aesthetic appeal. 

With multiple responsibilities to uphold, keeping retaining walls free of moss, algae, mold, and mildew stains are essential. Luckily, our guide on how to clean a retaining wall will walk you through how to get rid of these pesky organic growths. 

What’s Growing On Your Retaining Wall? 

The organic growth on your retaining wall is typically at least one of four or five things. Along with some visual clues, you can tell what’s spreading by observing where you find it: 

  • Algae need light, have no texture, and are usually green but sometimes red. 
  • Lichen requires sunlight and are green when wet but can take on a variety of colors when dry. 
  • Mold and mildew prefer darkness, have no actual texture and can be a variety of colors. 
  • Moss thrives in sunlight but can survive in darker areas, have tiny leaflets, and are usually green but sometimes black, brown, or yellow. 

Retaining walls are typically made from porous materials like concrete, stone, or wood. This allows organic growth to work their way below the wall’s surface, where they are challenging to remove. 

So, it’s better to attack whatever’s growing before it has a chance to truly take hold. Otherwise, the growths may permanently discolor or damage your wall as they burrow deeper. 

How to Clean Retaining Walls 

You don’t need a bevy of tools to keep the surface of your retaining wall growth-free. In fact, all you’ll probably require is Wet & Forget Concentrate. 

Wet & Forget Outdoor products are safe on almost every outdoor surface as they don’t contain acid, bleach, or phosphates. In addition, unlike bleach and other cleaners whose pH levels reach as high as 13, Wet & Forget Outdoor is more neutral, with a pH of 8. 

When used under the right conditions — cool days with a steady temperature of at least 32 degrees and no forecasted wind or rain  — a single application will clean your wall gently and over time.  

Depending on the humidity, climate, and weather, Wet & Forget can keep your wall clean of organic growths for up to a year or longer. 

If you live in a colder climate, be sure to apply the Wet & Forget concentrate when temperatures are above freezing.

How to Remove Algae, Mold, and Mildew From a Retaining Wall 

With Wet & Forget at your side, it’s time to start cleaning: 

  1. Dilute the Wet & Forget Concentrate with water in a pump up sprayer, using a 1 part Wet & Forget to 5 parts water mixing ratio. If you have a one gallon sprayer, add 20 oz (2 ½ cups of Wet & Forget) to your sprayer, and fill the rest with water up to the one gallon mark.  
  2. Spray Wet & Forget Outdoor onto any stains on your retaining wall until the surface is entirely soaked. 
  3. Keep pets and family away from the fence for 4 to 5 hours, as this is how long the product will take to dry. 

That’s it. The spray will work with wind and rain to gently clean the wall over time. 

Superficial green growths should disappear within a few days or, at worst, a few weeks. Black stains may take a month or two to disappear. Especially stubborn stains that have been on your retaining wall for years may take between six months and a year. 

Once the organic growth is gone, you’ll only need to apply the spray to your wall once a year. There’s no need for any scrubbing, rinsing, or power washing. 

How to Remove Moss and Lichen from a Retaining Wall 

Moss and lichen are slightly more complex organisms when compared to algae or mold. So, their removal requires just a few extra steps, though nothing sweating-inducing. 

To remove moss from a retaining wall: 

  1. Spray moss until it’s completely soaked through to the surface it’s attached to. 
  2. Wait a few days or weeks to see the moss turn brown and loosen up from the surface. Over the next few months, the rain and wind will remove the moss completely from your retaining wall. 

To remove lichen from a retaining wall: 

  1. Spray any lichen growths until completely soaked. 
  2. Wait 15 minutes, during which the outer shells of the growths should begin to soften. 
  3. Spray any lichen growth until completely soaked again. 

As Wet & Forget Outdoor needs time to penetrate the outer layer of lichen growths, avoid spraying on sunny days. Otherwise, the spray may evaporate before it finishes its work. 

Should You Use a Power Washer to Clean Your Retaining Wall? 

Power washers can be a tempting tool at first. However, when you combine the hassle and expense of renting one with their high level of ineffectiveness, that temptation should quickly melt away. 

Sure, they may remove a surface stain, but they can also push the organic growth deeper within the porous materials of your retaining wall. This allows the source of the stain to linger while also making its removal even more difficult. 

When you use a power washer, you may also strip color from the surface of your retaining wall or damage it. If pieces of concrete or stone get blasted away, they can become more susceptible to organic growth. 

Finally, power washers are messy. You are just as likely to end up with a mud-splattered retaining wall as a clean one. 

Where Can You Find Wet & Forget Products? 

Keeping your retaining wall free of organic growths is one of the best things you can do to maintain it. So, head online or to your nearest retailer to pick up some Wet & Forget Outdoor today!