Q&A / 

Clean Algae Off Siding

Clean Algae Off Siding

Clean Algae Off Siding | This is typical green algae on fiber cement siding. Liquid soap and Stain Solver will make the siding look like new.

Clean Algae Off Siding - Liquid Soap and Oxygen Bleach

Not a week goes by that I don’t get a question about cleaning this or that. These questions flow through the Ask Tim page on my www.AsktheBuilder.com website. As it turns out, I happen to know lots about cleaning things.

I attribute much of this to the formative years I spent working at Skyline Chili in Cincinnati, Ohio. I worked there after school during high school and most of college. I became an expert string mopper. You wouldn’t think there’s an art to moping a floor, but trust me, there is. I found out the best way to get grease off surfaces. I also washed tens of thousands of dishes, polished chrome, and discovered the magic way to get windows crystal clear.

How Do You Clean Algae?

This time of year, though, I get inundated with requests about how to clean algae from every conceivable outdoor surface. It might be green or black algae. It might be simple mildew.

Let’s start with why the algae thrive. My college major is geology, not biology, but I can tell you the algae need food and it needs water. Dust, aerosol tree sugars, biomass from soil splash, etc. are all foods that can collect on horizontal and vertical outdoor surfaces. If you deprive the algae of food, it can't grow. It's impossible to stop the water component because humidity, rain, morning dew, etc. are all beyond your control.

When Should I Clean The Algae?

It’s not much different than you and me. Knowing this, you can prevent algae growth by keeping the surfaces clean that you want to look great. Just as you probably shower each day to prevent body odor, it’s wise to wash outdoor surfaces on a regular basis. Once they start to look a little dingy or you see a very light haze of algae starting to take hold, it’s time to take action.

Should I Use a Pressure Washer?

Here’s what not to do, in my opinion. Do NOT use a pressure washer. These machines generate such high pressure that they can peel the paint off wood, they can actually erode wood fibers, and they can squirt water behind the exterior surfaces of your home where water should not be.

pressure washer

What is the Biggest Mistake Made Using a Pressure Washer?

The biggest mistake I see homeowners and pros make is they aim the wand up. In other words, they stand on the ground or a ladder and try to clean surfaces above their head.

I’ve got news for you. The way we build homes is we count on water coming down from the sky, not blowing up from below! Lap siding, flashings, etc. are all designed to shed water that is flowing towards the center of the earth, not shooting to outer space for goodness sake.

What Can Go Wrong Cleaning Vinyl Siding Using a Pressure Washer?

If you clean vinyl siding with a pressure washer, you might be forcing gallons of water behind it when you get next to a vertical seam in the siding, at a corner post, or next to a window or door. If you aim the water stream the wrong way towards the overlap or the trim pieces, the water can easily be blown behind the siding.

What is the Best Algae Cleaning Solution?

I’ve had fantastic success cleaning algae from just about every outdoor surface using liquid dish soap. I also like to use Stain Solver, a certified organic oxygen bleach. I also employ my favorite exterior cleaning brush. This brush is one that’s made to clean RVs. It’s got lots of bristles that are about 2.5 inches long and they’re soft. They won’t scratch automotive paint, so it’s safe to use it on your house siding, windows, and every other surface. I’d use a normal scrub brush with aggressive bristles to clean algae from any masonry surface either vertical or horizontal.

Should I Use Chlorine Bleach to Clean Off Algae?

Whatever you do, do NOT use chlorine bleach in your cleaning solution. Do not use any product that contains chlorine bleach. You can identify this by looking for its chemical name on the label: sodium hypochlorite. Chlorine bleach is toxic to all of the plants, trees, flowers, etc. around your home you want to keep safe.

I witnessed my neighbor years ago slowly poison a stunning tall maple tree. Each spring she’d pour gallons of chlorine bleach on her patio to clean off the algae. The tree shaded the patio and all the roots were under the patio stones. I warned her about this, but she treated me like I was a dolt. Oh well, the tree eventually died and she had it cut down.

Are the Easy Spray-On Cleaners Good?

I’d also caution you about purchasing these miracle products that say you just spray them on and walk away. I did a survey in my free AsktheBuilder newsletter about these products and the overwhelming response was that they’re worthless.

Common sense tells you these miracle products are too good to be true. Think about it. The way you get surfaces clean is you must mechanically agitate the surface to break the bonds of the dirt and algae.

How Do You Get Things Clean?

Here’s an example. Assume you’re filthy and sweaty. If you just jump in the shower and let the warm water cascade over you while you stood perfectly still, you’d come out of the shower dirty. Imagine what the towel would look like! You get clean because you use your hands with soap and rub your skin, then you rinse off the dirt.

The same is true when cleaning clothes. Imagine taking a load of dirty clothes and putting them in a giant stainless steel tub. Add water and soap and just let them soak for three days. Empty the water. Look at the clothes. They’ll still be dirty. Clothes get clean in your washing machine because the machine agitates them. The clothes rub against one another and this removes the dirt with the help of the soap.

Cleaning algae is easy. Just use common sense, soap, water, and the right brush!

Column 1409


4 Responses to Clean Algae Off Siding

Leave a Reply

Your email address will not be published. Required fields are marked *