If you are trying to clean dirt, mold, mildew, fungi, etc from your roof, you have the choice of using either a pressure washer or a soft wash solution and rinse. While both of these methods can remove stains and dirt from your roof, there are significant advantages to using the soft wash method.
The first advantage is in how the roof is actually getting cleaned. With a pressure washer, water is sprayed on the roof at a high pressure to basically break up the gunky build up and blast it off the roof shingle. While this appears to be effective at first, the mold and fungi are going to reappear sooner than you would like. This is because the power washer only removes the top layer of build up. It rarely penetrates deep into the shingles to remove the problem completely. Also, it does nothing to help prevent more mold and fungi from moving back in. With the soft wash method, a cleaning solution is first applied to the roof. This solution is usually made of a combination of mildewcide and fungicide to penetrate deep into the shingles and kill any mildew, mold, and fungi that have colonized on the roof. After a short time, a soft water rinse (about the pressure of an ordinary garden hose) is applied to the roof to rinse away the cleaning solution and the now dead organic material. As a result, the roof is cleaned and the cleaning solution should help to keep mold and fungi from reinhabiting the roof for a while.
The second advantage is that a soft wash method will not damage your roof or property in any way. It takes great care and skill to use a pressure washer without the risk of damaging your property. Most of the time, the pressure washer will force water between the shingles, into any tiny cracks and splits in the shingles, and can even blast off the top layer of the shingles. This can lead to significant damage to the roof, resulting in an early roof replacement. The only material that a power washer can safely clean without risk of damage is concrete. Otherwise, damage can easily occur. With a soft wash method, the risk of damage is completely removed. The soft wash uses nothing more than a garden hose pressure, which is not enough pressure to cause property damage. There is no pressure that forces the water into unwanted areas or that will remove any layer of shingle. This method allows you to effectively clean your roof without the unnecessary risk of roof damage.
When choosing a method for cleaning your roof, the choice is easy. Why take a risk and damage your property only to have the problem quickly return? Use the soft wash method. It is far safer and more effective than using a power washer.