How to Kill Moss on Concrete

Although you usually find moss in shady, damp areas with little air circulation, it can quickly grow on your concrete driveway, patio, and sidewalk. 

Moss isn’t harmful to concrete, but it causes the surface to become slippery to walk on, not to mention detracting from your home’s curb appeal.

Fortunately, there are a few simple and effective ways to kill moss on concrete. 


How to Kill Moss on Concrete

Let’s take a look at some standard moss-killing methods:

Pressure Washer

One of the quickest and most effective ways to remove moss from concrete is to blast it off with a pressure washer. This method is best suited for large concrete areas like driveways and patios.

Be sure to use the proper nozzle for your pressure washer. 

Start with a wide-angle nozzle at first to avoid damaging the concrete surface. Move up to the yellow 15° nozzle for stubborn moss you can’t get rid of. 

Adding a detergent or cleaning solution to break down the moss is also helpful.

Vinegar Solution

Vinegar is a natural acid that can kill moss without damaging concrete surfaces. 

Mix equal parts of water and white vinegar in a spray bottle for this method. Alternately, most grocery stores will sell white vinegar formulated explicitly for cleaning. You can usually find this with the other cleaning products, not near the cooking vinegar. 

Spray the solution onto the mossy concrete areas and let it sit for 30 minutes to an hour. The vinegar will kill the moss and help loosen it from the surface of the concrete. 

Use a stiff brush to scrub away any remaining moss and rinse the area with water to remove any residual vinegar.

Baking Soda Solution

Baking soda is another natural substance that can be used to kill moss on concrete. 

Simply sprinkle baking soda generously over the affected concrete areas. You can leave it for several hours or even overnight before sweeping it up. 

The baking soda absorbs the moisture in the moss, causing it to become dried out, crumbly, and easy to sweep away.

Bleach Solution

If you’re looking for a more heavy-duty solution, you can use bleach to kill moss on concrete. This method is best suited for small areas of moss growth.

However, you don’t want to overdo the bleach solution’s potency. Stick to a mixture of one part bleach with four parts water. 

Apply the mixture to the mossy concrete areas and let sit. 

After a few days, the moss will gradually die and lighten in color. Once it has dried, sweep up the moss and rinse the area with water. 

Always use bleach in a well-ventilated area, as the fumes can be harmful.

Boiling Water

Another quick and easy way to kill moss is to pour boiling water over it. 

This method is best suited for small patches of moss. Boil a pot of water and pour it over the mossy concrete areas. 

The heat will kill the moss, and the roots will be lifted from the surface, making it easy to sweep away.

Using boiling water to kill moss is a great, environmentally-friendly option as it doesn’t require the use of any chemicals.

Moss Killer Sprays

Several commercial moss killer sprays are available, which can effectively kill moss on concrete.

Like bleach or vinegar, spray the affected concrete areas with the solution and let it sit for 24 hours. This kills the moss, turning it brown or black. Then, wash away the dead moss with a garden hose or pressure washer.

Be sure to follow the instructions on the product label carefully and take precautions to avoid damaging the concrete surface.

Pressure washing moss on concrete stone

Factors to Consider

When selecting a method for killing moss on concrete, there are several things you should consider.

Severity Of The Problem

The first thing to consider is the severity of the problem. If you only have a few patches of moss, boiling water or a commercial moss killer spray may be all you need.

However, if the problem is more widespread, it calls for a more heavy-duty solution like a power washer.

Safety

Another thing to consider is safety. Some methods, such as bleach or boiling water, can be dangerous if not used properly. It’s essential to read the instructions carefully and take precautions to avoid harming yourself or damaging the concrete surface.

Cost

Of course, the cost is another crucial factor to consider. Some methods, like power washing, can be pretty expensive. If you’re on a budget, you may want to try a less costly method like boiling water or using a commercial moss-killer spray.

Efficacy

Finally, you’ll want to consider the efficacy of the method. 

Some methods, like power washing, are very effective at killing moss. However, they can also damage the concrete surface if not used properly.

On the other hand, some methods, like using vinegar, are less effective but won’t damage the concrete.


Preventing Moss Growth

Once you’ve removed moss from concrete surfaces, it’s essential to take steps to prevent it from coming back. 

Here are several tips:

Reduce Moisture

As mentioned earlier, moss thrives in shady, damp areas with little air circulation. One of the best ways to prevent moss from growing on concrete is to reduce the amount of moisture in the area.

Trim back any overhanging trees or shrubs that create shade and increase humidity. If you have gutters, ensure they are clean and free of debris so they can drain properly. You should also repair any cracks or holes in concrete surfaces as these can allow moisture to seep in.

Increased sunlight will also help dry out the area and prevent moss from growing.

Clear Debris

Debris accumulation is one of the main reasons moss grows on concrete, so it’s important to keep surfaces clean and debris-free. Regularly sweep or rake leaves, twigs, and other debris from concrete surfaces.

You should also clear gutters and downspouts so they can drain properly. Clogged gutters can cause water to pool on concrete surfaces, which creates the perfect environment for moss to grow.

Apply Moss Prevention

Several products on the market can be applied to concrete surfaces to prevent moss growth. These products typically contain copper or zinc sulfate, killing moss spores and preventing them from germinating.

Be sure to follow the instructions on the product label carefully and take precautions to avoid damaging the concrete surface.

Increase Sunlight

It’s much more likely that concrete surfaces in damp spots that don’t get a lot of sunlight will develop moss. 

To prevent moss from growing, try to increase the amount of sunlight that hits the surface.

As before, this can be done by trimming back any overhanging trees or shrubs that create shade. You should also move any outdoor furniture or planters blocking sunlight if possible.

Clear Snow and Ice

Believe it or not, moss can grow in cold weather as well. 

When snow and ice accumulate on concrete surfaces, it creates the perfect environment for moss to grow. Clear away snow and ice as soon as possible to prevent this.

You can use a shovel or snow blower to remove the snow or sprinkle an ice-melt on icy patches. 

Just be sure to use ice melt sparingly, as it can damage concrete surfaces.


Frequently Asked Questions

Let’s take a look at some common questions regarding how to kill moss on concrete:

Is moss harmful to concrete?

Moss itself is not harmful to concrete. However, the roots of moss can penetrate small cracks in concrete and cause further spread of the problem. Additionally, moss can hold moisture against concrete surfaces, leading to freeze/thaw damage.

What is the best time of year to kill moss?

The best time of year to kill moss is in the spring or fall when temperatures are mild. Moss treatment can also be done in summer, but taking precautions is essential to avoid damaging the concrete surface with too much heat.

Can I just leave the moss alone?

Moss is not immediately harmful to concrete but can cause damage over time if left unchecked. Additionally, moss can be unsightly and make your concrete surfaces look dirty. 

If you don’t mind the moss, you can leave it alone. 

How does moss cause damage to concrete?

Moss can cause damage to concrete in several ways. 

If allowed to establish, moss holds moisture, leading to concrete deterioration. It can also lead to thawing and moisture freezing in the concrete, which causes cracking.

Is moss harmful to pets?

If you have pets running around your yard, you may be wondering if moss is harmful to them. For example, if your dog eats moss, will it make them sick?

The answer is no. Moss is not harmful to pets. However, some commercial moss killers may contain chemicals that can be harmful if ingested. It’s important to read the label carefully and take precautions to keep your pets safe.