how to remove moss from roof

How to Remove Moss From Your Roof

Moss may look nice on your roof, but the benefits stop there. In reality, moss poses some significant threats to the long-term health of your roof-especially if you have a shingle roof.

  • It can grow underneath roof shingles and start to uproot them, leaving them especially vulnerable to getting blown off in higher winds.
  • Its roots can grow into shingles and weaken their protective abilities.
  • It harbors moisture in its leaves, causing disintegration of your shingles.
  • The increased moisture on your roof can lead to damage in the roof deck and even leaks.

Not as simple as it sounds

Moss removal may seem simple enough. But it’s actually quite easy to cause further damage to your roof if you don’t take the right precautions. You want to be a moss killer, not a roof killer.

Here’s our 3-step process for killing moss and avoiding roof damage in the process:

  1. First try and see if a simple scrub will do the trick. Gently hose down the affected area and scrub lightly with a soft-bristle scrub brush. Spray and scrub in the direction of top to bottom.
    • Take care not to spray the water with too much pressure, scrub too hard, or spray/scrub in the direction of bottom to top. All of these actions will damage the granules of asphalt shingles and weaken your roof.
  2. If the moss remains after step 1, a cleaning solution is your next move. There are a number of quality cleaners sold in stores as well as some DIY options (see the next section). The next time you have a cloudy day, head up to your roof with your hose, sprayer and scrub brush. Spray the mossy parts with your cleaner, then wait 15-20 minutes before lightly scrubbing and hosing down the area (again using a low-pressure garden hose).
    • You’ll want to do this on a cloudy day to avoid the sunshine drying out the cleaning solution too quickly. 
    • If you opt for a DIY cleaner, make sure it doesn’t include too much chlorine bleach, which will damage your roof (see the next section). 
    • You also may want to consider covering any plants below with plastic sheeting to avoid damage from the runoff.
  3. If the moss remains even after these first two steps, you’ll want to call a professional to come assess the situation so that you aren’t stuck spinning your wheels or risking further damage to your roof.

Which materials you should use and which you should avoid

To successfully clean moss off your roof you’re going to need:

  • A ladder to reach the affected roof surface safely (as well as a harness if you so choose).
  • A garden hose long enough to reach your roof
  • A soft-bristle brush
  • A spray bottle
  • A store-bought roof cleaning solution or one of these DIY alternatives recommended by IKO:
    • 1/2 cup (4 fl oz.) of dish soap + 1 gallon of water
    • 1 cup of white distilled vinegar + 1 gallon of water
    • 1 cup of chlorine bleach + 1 gallon of water

ACME Roofing mentions that you can also use lemon juice and baking soda in your concoction. If you need a slightly stronger cleaner, it can be up to 50% bleach. But you’re best off starting on the lower end. 

To avoid damage to your roof you should NOT use:

  • A bleach solution that is more than 50% chlorine bleach
  • A pressure washer. Pressure washing or power washing runs a high risk of cracking and damaging your shingles.

Where is moss commonly found on roofs? 

Moss growth is caused by two primary factors: moisture and shade. 

In the US, the side of your roof that gets the most shade is the north-facing side, and will be a common place to find any moss that might be growing on your roof.

How can you prevent roof moss?

Fortunately there are some preventative measures you can take to ensure your roof and gutters moss-free. Moss growth is caused by two primary factors: moisture and shade. So you want to keep both of those in mind as you keep a lookout for moss on your roof.

Here are a few ways you can defend your roof against the moss:

  • Nothing beats good ole fashioned roof maintenance. Regularly cleaning your gutters and clearing debris off your roof is the easiest, cheapest way to prevent much of the moisture that causes moss to form.
  • Trimming trees that are significantly shading your roof. 
  • Attach zinc strips along your roof ridge. The zinc catches the moss-causing properties of any water that flows over it.
    • It is worth noting, however, that this method does have some risks associated with it. If you nail the strips in, you run a risk of leaks. If you break the sealant bond to install the strips under the shingles, you run a risk of wind damage. So this option may be worth considering as a final resort.
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