Cleaning Shingles: Removing Dark Streaks

What You'll Need
Safety mask
Roof shoes that provide slip resistance
Long pants and sleeves (to protect exposed skin)
A harness system, and preferably a spotter
A non-conducting ladder
Liquid pool shock from a local swimming pool supply store
Fresh water
Large clean tank or container
Liquid laundry detergent
Hose the provides running water

There are correct and incorrect ways to clean shingles and remove dark streaks. While asphalt shingles perform the mammoth task of protecting homes and buildings from moisture and inclement weather, they are not indestructible.

It might be surprising to know that those dark streaks on the shingles are actually caused by algae, and not by the usual suspects of tar or dirt. Because the shingles hold moisture for long periods of time, algae can begin growing and actually feed off of the limestone in the shingles. If left untreated, the algae will continue to grow and eventually cover the entire roof.

How not to clean the shingles

There is one method that will not only remove the algae, but also take a few years off of the lifespan of the shingles. It is not advised to try to remove the algae with a high pressure sprayer. The pressure of the water can not only remove shingle granules, but it can also force water into sealed areas around skylights and chimneys, causing future leaking problems. While pressure washing seems like a quick fix, it can also do far more damage than the original algae.

How to clean the shingles

The safest way to remove the algae from the shingles is to use the right combination of cleaners, which makes pressure washing unnecessary. It may be possible to hire a professional to do this job, but if not, here are the requirements and the procedure.

Step 1 – Cover up

Wear the protective gear to prevent the cleaning solution from coming into contact with skin, eyes, or mouth. If that happens, rinse completely with plenty of fresh water.

Step 2 – Mix the cleaning solution

In the large tank or container, mix the pool shock liquid with equal amounts of fresh water. If the roof is steep, add a half a cup of liquid laundry detergent.

Step 3 – Apply the cleaning solution to the roof

This step requires special attention to safety because the roof shingles can become very slippery. Pour or spray the cleaning solution onto the roof as evenly as possible.

Step 4 – Rinse the roof

The next step is to rinse the cleaning solution off the shingles. The algae should come off easily with the fresh water.

Final Step – Rinse off all plant materials around the house or building

While the chlorine in the cleaning solution can destroy the algae, it can also damage any grass or plants that are growing underneath areas where the cleaner drained off of the roof. Use a hose with fresh water to spray the plants and dilute the cleaning solution.

The roof will look great and still last for many more years. It should be emphasized that extreme care should be taken when doing any kind of work on a roof.