How to remove mould and mildew from your roof

November 3, 2015

While most moulds just stain your roof, moss and lichen can cause damage to your roof over time. Therefore, it's a good idea to evaluate your roof annually and clean it if necessary. Here's a quick guide to doing just that.

How to remove mould and mildew from your roof

The types of mould, moss or mildew on your roof

Unsightly black stains on your roof that look like mould usually indicate that a type of algae is growing on your roof. This algae won't damage your roof, but it's unattractive.

Likewise, mildew is a sign of too much moisture, but it won't damage most roofing.

Lichen and moss, however, will damage your shingles. Moss will grow on your roof in fuzzy looking, deep green clumps. Lichen, on the other hand, usually looks like flat blooms of pale blue or green.

Lichen and moss hold water onto your roof. Since water is held there when these plants are on your roof, they can contribute to roof-weakening rot on wood or asphalt shingles.

How to remove debris from the roof

1. Prepare to work safely

  • When working on a roof it's important to wear a safety harness to prevent falls.
  • You should also wear long sleeves, full length pants, heavy boots, gloves and goggles as a safety precaution.

2. Scrub away moss or lichen

  • Once you're on the roof, you should use a soft-bristled scrub brush and water to remove any moss or lichen that's present.
  • Remember, these plants will cause rot on your roof, so it's important to eliminate all traces of them.
  • However, you should brush off the moss gently to prevent damaging the shingles.
  • Mould can be ignored during this step.

3. Spray down your roof

  • Heavily water any plant life around your house to protect it from any runoff that will occur in when you spray your roof.
  • Spray your entire roof with a mould- and moss-killing roof wash.
  • A simple handheld, manual pump sprayer can be used to wash your entire roof.
  • Never use a pressure washer when washing a roof; the chance you could inadvertently damage your shingles is too high.

Preventing future mould, moss and mildew

A bleach mixture or roof wash should kill any mould and algae and prevent it from returning immediately.

However, if you'd like to avoid cleaning your roof every year, you can install zinc or copper roofing strips near the peak of your roof. These metal strips will act as a mould and algae deterrent every time it rains.

If you have trouble with moss, you may want to consider cutting back trees that shade the roof, which allows the moss to grow. Otherwise, plan on using a roof wash that inhibits moss and mould growth every year to avoid manually removing any lichen.

Consider calling a professional

Removing mould and mildew from your roofing is a simple process, but it can be dangerous if you don't have the proper equipment or experience working on your roof.

If your budget permits, you should consider hiring a professional to clean your roof. If they're able, you might also want to have this person install metal roofing strips to help prevent future mould growth.

If you do decide to remove mould, mildew, moss and lichen from your roof yourself, be sure to use this quick guide as a starting point to help make sure you do the job safely and properly.

The material on this website is provided for entertainment, informational and educational purposes only and should never act as a substitute to the advice of an applicable professional. Use of this website is subject to our terms of use and privacy policy.
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