You Can Get Rid of Mold on Your Roof (and Keep It From Coming Back)

With the exception of a few sharp cheeses, mold is not something you want in or on your home. This is usually a sign of a more serious structural or ventilation problem, and not only is it often accompanied by that damp, musty smell, it’s also not good for our health .

While finding mold indoors may not be such an urgent issue, finding mold growing on your roof can be worrisome, especially if someone in your family has allergies or other respiratory issues, or you’re getting ready to put your home on the market and want to to make it look its best.

Here’s what you need to know about roof mold, including what it is, how to get rid of it, and how to prevent it from coming back.

Is there mold growing on my roof?

First things first: what appears to be mold covering your roof is probably something else. Since we are used to making sure it grows in our homes, we might assume that anything green or black on our roof is also mold, but this is often not the case.

In fact, when it comes to our roof, what we might call “mold” is usually algae or moss. Here’s how to tell them apart :

• Algae : May look and feel slimy, but are otherwise flat; usually appears as green, black, or blue-green stripes; often mistaken for mold.
• Mosses : Tiny green plants growing in dense textured mats; may become thicker and more sponge-like over time.
• Mold : Relatively rare on rooftops, but when it does, it’s likely the result of algae staying on the roof for too long, making shingles constantly damp and a good home for mold.
• Mold : A type of mold, usually black, red, or pink in color with a powdery appearance; grows in damp, shady places, but is rarely found on rooftops.

So, to recap: “mold” on your roof is probably algae, unless it looks and feels like a fluffy green carpet, in which case it’s moss.

Before starting the removal process

Doing any job involving your roof can be potentially hazardous, so please know your limits and be realistic in your abilities – and sense of balance – and call in a professional if necessary. If you are going to do the work yourself, take all necessary precautions , including wearing proper personal protective equipment such as gloves, goggles and a face mask.

In addition to getting rid of what is growing on your roof, you will use a bleach solution, which can also damage plants, grass, and trees that you want to have there. One way to get around this is to cover the ground around the perimeter of your home with plastic tarps to protect them from roof runoff.

If a tarp isn’t an option, water any plants and herbs growing along the house’s foundation before proceeding with the removal, and then again after you’re done to rinse them off.

How to remove mold and algae from a roof

Since moss removal requires additional steps, and your roof is likely to have algae growing, we will focus on algae and mold removal.

There are ready-made products you can buy to get rid of mold and algae, but you can make your own and they are just as effective and much cheaper. Simply mix a solution of half bleach and half water and pour it into a spray bottle.

Use a spray bottle to thoroughly coat the roof with the bleach solution, then let it sit for about 30 minutes . Then, starting with the shingles at the top of the roof, use the low pressure setting on your garden hose to flush out the bleach.

Never use a high pressure washer during any part of this process as this could damage your roof.

How to prevent mold and algae growth on your roof

Here are a few strategies you can try to prevent the return of mold and algae:

1. Copper or Zinc : Install 6″ wide strips of copper or zinc under the row of shingles closest to the top of the roof, leaving 1-2″ of the bottom edge exposed.
2. Trim branches that cover the roof: More direct sunlight means less moisture on the roof and a less favorable environment for algae and mold.
3. Keep the roof clean : regularly remove all leaves, branches and other debris that accumulate on the roof , as they retain moisture.
4. Clean the gutters : make sure that water can run off the roof.