Asphalt shingles are designed to protect a roof from weather, but aggressive cleaning can damage the surface they rely on for that protection. Soft washing uses controlled pressure and cleaning solutions to remove organic growth while reducing the mechanical force applied to delicate shingle granules.
Understanding Shingle Granules
In roof cleaning, asphalt shingles should be treated differently from hard surfaces such as concrete or metal. Their upper surface contains mineral granules embedded in asphalt, providing protection against ultraviolet radiation and contributing to the shingles’ weather resistance.
Excessive mechanical pressure can loosen these granules, particularly when shingles are already aged, brittle or deteriorated. Once granules are removed, the exposed asphalt can become more vulnerable to environmental degradation.
Examining Granule Function
Granules serve several purposes beyond appearance. They shield the underlying asphalt from sunlight and help create the textured surface characteristic of asphalt roofing.
Loss of granules can therefore shorten the effective service life of a shingle. Cleaning methods should remove algae, moss and other contaminants without unnecessarily disturbing this protective layer.
Identifying Roof Vulnerabilities
Not every asphalt roof has the same resistance to cleaning. Age, weather exposure, previous damage and shingle condition can all influence how much mechanical stress the surface can tolerate.
A roof that already shows bald patches, exposed asphalt or loose granules requires particular care and may need professional evaluation before cleaning.
Evaluating Soft Washing
Soft washing combines relatively low-pressure application with appropriate cleaning agents. Rather than relying primarily on force to remove biological growth, the cleaning solution helps break down contaminants so they can be rinsed away with less mechanical agitation.
The precise pressure used varies according to the equipment, roof condition and cleaning system. Therefore, 500 PSI should not be considered a universal safe limit for every asphalt shingle roof.
Comparing Cleaning Pressure
Pressure is only one part of the equation. The distance between the nozzle and roof, nozzle type, flow rate, cleaning solution and operator technique all affect the force reaching the shingle surface.
A machine capable of producing 500 PSI does not necessarily mean the roof is receiving 500 PSI directly. Professional technicians adjust their equipment and technique to control the force applied to the surface.
Reducing Mechanical Damage
Using controlled pressure can reduce the likelihood of dislodging granules compared with aggressive high-pressure washing. The objective is to allow the cleaning solution to do much of the work rather than attempting to blast contaminants away.
This distinction is particularly important when removing algae stains, moss or lichen from older roofing materials.
Protecting Asphalt Shingles
A proper soft-washing process involves more than choosing a pressure setting. The cleaning solution must be appropriate for the roofing material, and runoff should be managed responsibly to protect surrounding landscaping and property.
Several factors should be considered before treatment:
- The age and condition of the shingles.
- The type and severity of biological growth.
- The cleaning solution recommended for the roofing material.
- The direction and control of water runoff.
- The condition of gutters, flashing and surrounding surfaces.
These details help determine the most suitable cleaning approach.
Preventing Granule Loss
Protecting granules begins before the equipment is turned on. A professional inspection can identify fragile areas, existing granule loss and sections that should not receive aggressive treatment.
During cleaning, operators should avoid unnecessary abrasion and direct concentrated spray patterns that could disturb the shingle surface.
Managing Biological Growth
Algae and moss can make a roof look heavily stained, but simply increasing pressure is not necessarily the right solution. Biological growth may require an appropriate treatment that loosens or kills the organisms before rinsing.
This approach can deliver a cleaner surface while reducing the temptation to compensate for stubborn stains with excessive mechanical force.
Inspecting After Cleaning
Once cleaning is complete, the roof should be checked for remaining growth, damaged shingles and areas requiring further attention. Granules visible in gutters may also provide information about the roof’s existing condition, although some loose granules are normal in aging roofs.
Choosing Professional Cleaning
A 500 PSI setting can be compatible with certain soft-washing systems, but pressure alone does not determine whether an asphalt roof will be protected. Proper chemical treatment, equipment setup, roof assessment and operator technique all contribute to minimising granule loss.
Conclusion
Soft washing protects asphalt shingle granules by relying on controlled pressure and suitable cleaning solutions rather than aggressive mechanical force, while 500 PSI should be viewed as a system-specific figure rather than a universal limit. For a roof assessment and cleaning method suited to your shingles, consult a professional roof-cleaning company such as New Haven Pressure Washing.