More than any other part of your home, your roof takes a full-on beating virtually all year long. In addition to enduring drought, rain, snow, ice, wind, extreme heat, and cold, your roof is also a repository for stray debris, both living and nonliving.

It is no wonder your roof occasionally needs some TLC in the form of a soft wash.

The following explains why you should soft wash your roof, what doing so entails, the benefits you will see, and how often to do it.

What Is Soft Washing a Roof?

Soft washing a roof is a cleaning technique that uses a low-pressure wand or gun to spray clean and water over the surface of your roof to remove stains and foreign debris. A soft wash done correctly will allow the cleaner to penetrate through the debris down to the shingles, kill any living debris and then let a rinse of water remove it.

Some of the foreign debris that might accumulate on your roof includes, but is not limited to:

  • Dirt and dust
  • Mold
  • Algae
  • Lichen
  • Fungi
  • Moss
  • Gloeocapsa Magma (a bacteria that causes black stains on your roof)
  • Fallen branches and tree parts

The only difference between a soft wash and a power wash is the water pressure. While a soft wash uses a low-pressure system, a power wash uses a high-pressure washer.

Are All Those Things Harmful?

The good news is that roof debris, except for some types of mold, are generally not harmful to humans. The bad news is that several can lead to roof-rot, heat reflection reduction, and shorten the lifespan of your roof.

The impact of the debris on your roof varies depending on the following:

  • Area of exposure
  • How long since the roof was last washed
  • Whether the last washing permeated down to the shingles
  • How extensive the exposure is

What Are the Benefits of Soft Washing a Roof?

Soft washing your roof has the obvious effect of giving it a deep clean that looks great. In addition, though, several benefits are associated with soft washing your roof at least once a year.

Removes Dirt and Debris

Dirt, dust, twigs, and leaves all accumulate on your roof and, if not washed into your gutters, build up and eventually provide an anchor spot for moss and mold. Debris such as branches or twigs provides a place for other debris to collect and can transfer some living organisms to your roof. A thorough washing removes dirt and debris and kills anything living on your roof.

Kills Mold, Bacteria, and Algae

These living substances can lead to accelerated roof decay, discoloration, and in bad cases, an infestation that can spread to other parts of the house’s exterior. In and of themselves, all three can serve as a source of dampness and lead to roof decay and if they spread to painted or exposed wood on the house’s exterior, it can lead to accelerated rot.

Removes Moss

Moss by itself is harmless. However, the dirt that moss clings to can lead to moisture penetrating beneath the shingles, leading to rot. Also, moss will provide a place for mold, bacteria, and algae to grow.

Another risk is if the moss and dirt break off in a bad storm and end up falling into and clogging your gutters. That can lead to all sorts of problems, particularly if you do not know the situation exists.

Protects the Roof and House Walls

Your roof endures more than almost anything else in your home. A soft wash protects your roof, cleans it, and keeps it clean. The better maintained your roof is, the longer it will last you.

Also, living things on your roof can migrate to your house’s walls. When that happens, particularly if you have an older home made of a lot of exterior wood, substances like mold or algae can take hold and contribute to discoloration, peeling paint, and rot. If your home has siding, the mold can get behind the facade and begin an infestation.

A Good Opportunity for Inspection

Soft washing your roof gives you a great opportunity to perform a maintenance inspection. As you survey the surface for any foreign matter mentioned above, look for other signs of wear, tear, or needed repairs. Using the washing opportunity for an inspection is smart because many people forget to inspect their roofs until they have a problem.

Curb Appeal

The following are some foreign matter that gets on roofs and can lead to a diminished aesthetic appeal of your home:

Gloeocapsa Magma

Gloeocapsa Magma creates those black streaks on roofs, particularly in humid areas.


Mold can lead to general discoloration of your roof that can appear as bluish-green, black streaks or as splotches of lighter material across your roof.

Moss and Lichen

Mold and lichen can be attractive on the right house, but both generally detract from most roofs’ look. While harmless, each indicates organic matter that resides underneath them and can discolor your roof.

Dirt and Dust

Dirt and dust can create a general look of dirtiness on the roof. Dingy-looking roofs often combine mold, dirt, dust, and Gloeocapsa Magma.

Branches and Twigs

These can make a house look unkempt.

Some Temperature Control

Accumulated debris both thwarts the ability of shingles to reflect the sun’s rays and absorb heat. Additionally, they serve as heat conductors and can make the roof’s surface much hotter on warmer days. In cold weather, they hinder the ability of a roof to absorb the sun and can cool the overall surface of the roof.

How Does the Soft Wash System Work?

For the benefits you receive, imagining an easier way to rid yourself of junk on your roof is difficult. Here is how the soft wash system works.


The system starts with inspecting the roof to identify potential problem areas.

Water Rinse

Once you have inspected your roof and identified areas to focus on, the next step is to rinse your roof with water. The entire area you are cleaning should be thoroughly soaked to ensure the cleaner’s effectiveness and to wash away any loose debris.

Chemical Clean

After that, you spray the roof with whatever cleaner you have chosen to use. The cleaner should loosen dirt, moss, and algae and kill bacteria, mold, and mildew.

To ensure you are doing it correctly, research your type of shingles and see what the shingle manufacturer recommends for cleaning. Using the wrong cleaner can negate any warranty you have on the roof or its shingles. The wrong cleaner can also damage, weaken and discolor shingles.

Once you cover the roof in cleaner, let it sit for 60 minutes.

Water Rinse 2

After the cleaner has sat for at least an hour, rinse the cleaner with water.
Repeat as needed.
If your first wash and rinse do not remove everything, you may have to do it again.

Spraying Tips

When spraying, it is important to start at the top of the roof and work your way down, as this helps uproot any growth on your roof. Starting at the top allows you to see where you are working easily.

The sprayer should soak the roof’s surface, not beat the shingles. If the spray removes the shingle covering, you are using too much pressure. Adjust it to a lower spray pressure, or you might have to look at other spraying options.

How Long Does Soft Washing a Roof Take?

The length of time it takes to soft wash a roof depends on a few factors:

  • How large your roof is
  • The type of sprayer you are using
  • Whether you have to do one or two washing sessions

How Often Should I Soft Wash My Roof?

The minimum answer to this is once a year. Many roofs need it once a season. How often you do your roof depends on how clean you want it to be.

When Should I Soft Wash My Roof?

Sometimes, even if your scheduled cleaning is a few weeks or months away, a soft-wash cleaning is a good idea.

When It Is Dirty

A soft wash is good if your roof looks discolored, dingy, or dirty. Staying on top of keeping your roof clean is never a bad idea. If you follow the manufacturer’s advice, you are not risking harming the roof by too much cleaning.

When It Starts to Discolor

Some foreign matter discolors roofs. If you clean your roof as soon as you see black streaks or splotches that should not be there, you can nip an outbreak of mold or bacteria before it becomes a major chore to get rid of it.

When It Is Humid

Humidity is the friend of just about everything that can grow on a roof. More frequent cleanings are a good idea if you live in a humid area.

Once a Year

At a minimum, you should perform a roof cleaning by soft-pressure washing once every year.

Final Thoughts

Giving your roof shingles a soft wash cleaning once a year helps keep your roof looking great and extends its lifespan. If you do not want to wash it yourself, you can always hire roofing professionals to do it for you. Regardless of who cleans your roof, you can rest assured that your roof will continue to give you the protection it does for many years.
This article was written by Louis Hanley, community manager for Baltic Roofing where they help the greater Chicago community with everything from high-quality roof replacements to skylight repairs. He is an expert on all things roofing and home improvement. Outside of work, he’s a huge Cubs fan and enjoys spending time with his dog, Roscoe.