Cleaning Algae Off Your Asphalt Roof Using Homemade Cleaner

If you have start to see black streaks on your roof, you may be worried that the shingles are beginning to deteriorate. However, this is most likely algae growing. Because it can cause the asphalt to break down, it should be cleaned off. Below is how to do this using a homemade cleaner using ingredients you can find at department and home improvement stores.

Before You Start

Before you begin preparing the solution and cleaning your roof, keep the following tips in mind to make the job go more smoothly.

  • Plan to clean your roof on a cloudy day. The cleaner will need to soak in for several hours and the sun would cause it to evaporate too fast.
  • Dress the right way for the job. Wear old clothes that you do not mind ruining. The bleach and trisodium phosphate will both make colors fade on fabric.
  • Also, wear slip-resistant boots. The cleaner will make the roof slippery and you will need the extra traction.
  • If you have any treasured plants or bushes on the ground below, cover them with plastic to keep any overspray from damaging or killing them.
  • Protect your hands and eyes by wearing rubber gloves and safety glasses. The cleaner could irritate your skin and membranes if you accidentally get some on you.

Preparing The Cleaner

Before you go up on the roof, you will need to prepare the cleaner. This homemade solution uses bleach and trisodium phosphate, or TSP, to kill the algae at it roots, as well as any spores that have become embedded in your shingles. The TSP will also form a protective barrier to prevent any new growth for a couple of months.

What You Will Need

Below is a list of the ingredients and supplies you will need to mix up the cleaner.

  • One Gallon Of Warm Water
  • Four cups of household bleach
  • Half of a cup of trisodium phosphate
  • Two or five gallon pump sprayer


After you have gathered your ingredients, follow the directions below to mix up your homemade algae-killing spray.

  1. Fill the pump sprayer with the warm water.
  2. Add the bleach and TSP to the water.
  3. Close the lid and shake vigorously to make sure the cleaner is mixed well.
  4. Prime the sprayer hose by spraying for ten seconds.

Cleaning The Roof

Once you have your solution mixed and sprayer primed, it is time to go up on the roof and start killing the ugly algae. Along with your pump sprayer, you will also need a garden hose with a spray nozzle and a soft-bristled scrub brush.


  1. Use the garden hose to wet the area where you will be cleaning.
  2. Spray the roof with the cleaner until it is saturated.
  3. Use the scrub brush to work the solution into the roof. Use gentle, circular motions to prevent damage to the shingles. If you prefer, you can also use an old broom so that you do not have to kneel down.
  4. Allow the cleaner to soak in for four hours to ensure it penetrates deep into the pores of the asphalt.
  5. Rinse the roof using the hose and allow it to air dry.
  6. Seven days later, repeat the above steps. This will ensure that any algae growth or spores that were missed will be killed.

By using this cleaner every three months, you can keep the algae from building up on your roof. However, if you do notice that the shingles are starting to wear down, you may want to contact a professional roof repair service. He or she can inspect the damage and let you know whether you need roof repairs or replacement.

About Me

Home Renovation Expectations: Knowing What's To Come

When I bought my first house, I did it with the expectation of needing to do some remodeling. I wasn't, however, prepared for how complex the renovation process was. From upgrading the retaining walls to adding cosmetic features like the stone patio, I was inundated with decisions to make and materials to select. I wished that I had known how much was involved from the beginning so that I could be better prepared. That's when I decided to use what I'd learned to help others better prepare for their own remodeling projects. I hope the information here helps you to see what you can expect as you get ready to expand your property or renovate the existing space.



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