Archive for the ‘Kitchen Home Improvement’ Category


How To Remove Black Streaks And Mildew A Roof?

By Linda Bockman

Roof cleaning is not an exact science, most contractors charge anywhere from .50 cents a foot up to $1.50 depending on the pitch of the roof and the difficulty of the job. It’s a niche market that very few companies specialize in but those that do find it incredibly profitable.

Residential roof cleaning is another service that you can offer to your clients but it’s important that you understand the basics of roof construction. If not, you may cause leaks and severe damage in the home, most power washers use machines capable of pumping 4-8 gallons of water per minute, one mistake and I’m sure you can realize just how much damage you can cause if your not careful.

Most roofing materials are installed over a layer of felt paper and in some cases a rubber like ice guard material. The first layer of shingles is called the starter course and is installed at the lowest point on the roof, upside down. This allows a solid base for water to run over without leaking down into the rafters and plywood between the shingles keyways. Once this later is installed another shingle is place directly on top of it, and the rest of the roofing is placed in a similar fashion up the roofline. The reason shingles are installed in this manner is to allow the water to run over one shingle onto the next until it enters the gutter system. Now that you understand the basics of roof installation it’s equally important to know the other structures on the roof and their function to avoid causing leaks around them.

Vent Pipes

Vent pipes are used to vent gasses from plumbing fixtures in the home. The have a rubber gasket around them that wraps tightly around the protruding pipe to keep out water. Inspect all vent pipes to make sure there are no cracks or tears in them.


Flashing will be found where chimneys and other objects meet the roofing. It should be fastened and sealed in place to keep water from entering the home when it runs down the surface.

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Ridge Vents or Peaks

This picture shows the peak of a roof with the ridge vent removed so you can see where any water entering it will enter the home.

Nail Pops

Nail pops may only be small holes in the roofing but they can allow water into the home and under the shingles and felt paper. When water gets under the tar paper it can become trapped and cause the plywood underneath to rot.


Skylights may be found on many roofs and require extra caution. Never spray water around them, they will usually leak if you do.

Powered Attic Vents and Missing Shingles.

Most homes have motor driven vents on their roofs to remove excess heat on hot summer days. If water is sprayed under these vents it can easily run down the wires causing a short in the electrical system or a fire. Obviously it’s also important to make sure there are no missing shingles before you begin washing the roof. All of these items an easily be fixed by an experience roofer but it’s imperative that they are fixed before you clean the roof!

The Process

There are a few ways to clean roofs but they all rely on the same principle, low pressure cleaning with the use of a cleaning agent. Most roof cleaners use a sodium hydroxide base or sodium Hypochlorite. Bleach is used most often, but sometimes with disastrous results. GAF roofing says that the use of bleach immediately voids any warranty on an asphalt roof because it breaks down the composition of the shingle. These stains are impossible to remove without the aid of chemicals. Caustics are inexpensive and very effective for killing mold. No matter which method or cleaner you use they can cause significant plant damage around the home or to the roof if not used properly. Safety is also a huge factor in roof cleaning, using an OSHA approved safety harness and ropes are a must. Never attempt cleaning a roof without proper safety precautions; even the flattest roof can become slippery and hazardous when wet.

Most roof cleaning requests will be for removing green mildew or black streaks and stains (mold algae also known as ‘gloeocapsa magma’). These stains significantly affect the look of any home. On occasion you will also notice moss growing on roofs, what the home owner may not realize is that mildew and moss can actually eat away the roofing on the home.

In the past, the only way to get rid of them was to replace the roof. It has been estimated that as much as 50% of all roof replacements have been done because of the appearance of the roof and not actually because of its functionality.

We suggest using the following method: First, using an X-Jet, wet the roof slightly to cool it down. Also soak the ground and any plants near the downspouts to dilute the cleaner. Second, using a chicken ladder along with a roped harness or another OSHA approved method, apply your roof cleaner. This can be done with an X-Jet, pump up sprayer or Shurflow pump, no matter which method you use apply it to the shingles from the lowest part of the roof up to the peak. When applying cleaners make sure you don’t shoot them under the shingles, if using an X-Jet shoot above the roof and allow the cleaner to ‘fall’ onto the roofing like rain. After applying your cleaner, allow the cleaner to work for about 15 minutes then begin power washing with 100-300PSI from the peak of the roof down. Always make sure the spray from your wand is aimed down the roof, never across or up the incline. This will shoot water under the shingles and cause leaks. It will also get cleaner on the nails that fasten down the shingles. Most roof cleaning chemicals will cause rapid rusting of fasteners.

Finally, rinse the surface and plants around the area well. Rinsing of the roof can be done from the ground using your X-Jet.

About the Author: Linda Bockman 301-519-9274


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