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Asphalt Roofing Granules: What Are They, What Do They Do, and What Happens When They Erode?


If you have asphalt shingles on your roof, you've probably heard something about roof granules. The granules make up the rough surface of the shingles, and they are more important than many people realize. In fact, they are so important to your roofing system that seeing bald shingles or seeing granules in your gutters is a clear sign of roof damage. Most of the granules that you lose are eroded away through normal wear and tear, but there are things that you can do to preserve them. Let's take a closer look at what asphalt shingle granules do, what it means when they erode, and what you can do to prevent or repair damage to your roofing system.

What Are Asphalt Roofing Granules?

The granules make up the outermost layer of your asphalt shingles. They are made from hard stone that is crushed and screened into specific granular size specifications. Some of these granules are first applied to the shingles as-is in their natural stone-colored state, while an outer layer is processed into a variety of colors through ceramic firing. These long-lasting colors give the shingles a more attractive appearance when they are installed on your roof. Some asphalt shingles have algae-resistant granules that prevents discoloration caused by blue-green algae, which is common in humid climates. There are also reflective granules that reflect more of the sun's heat energy and reduce the heat that is transferred into the home. These granules are required by code in some regions.

What Do Asphalt Roofing Granules Do?

As you could probably guess, the granules on your shingles do serve a purpose other than making your roof look nicer. First of all, the granules are what give your shingles the ability to shed water, something that is crucial to your roofing system. Without granules, water could pool on your roof, seep into your home, and cause thousands of dollars' worth of water damage. Second of all, the granules provide protection from UV radiation, especially those that are designed to reflect a higher percentage of the sun's energy. Asphalt shingles also provide some measure of fire resistance to your roof. While wooden shingles burn rather quickly, asphalt shingles can last as long as two hours in a fire before they burn. Naturally, this property is lost when the shingles lose too many granules.

Finally, the right asphalt shingles can improve your home's curb appeal. Most people imagine asphalt shingles to be either grey or black, but there are plenty of other colors available if you want something that better complements the rest of your home's exterior.

What Happens When Asphalt Roofing Granules Erode?

When they are properly installed on a well-ventilated roof, asphalt shingles can last for over 20 years. However, the granules will erode over time. They can degrade in particularly harsh sunlight over several years, and they can be loosened by rain, snow, strong winds, or debris hitting your roof. Your shingles need granules to be effective. Without them, you might as well have a sheet of tar paper over your house instead of shingles. Water is more likely to damage your roof and cause a leak, your home won't be nearly as energy-efficient without your shingles' ability to absorb heat, and your home will be more susceptible to fire damage.

Preventing Granule Erosion

Technically speaking, there is no way to completely prevent your shingles from losing granules. Your roof is exposed to the elements at all times, and the fact that it does take a beating means it's doing its job. There are things you can do to extend the life of your roof and your shingles, however. First of all, be careful if you ever pressure-wash your home. Pressure washing vinyl siding is one thing, but a process that involves spraying your home with water at a high pressure will loosen shingle granules. In other words, don't pressure-wash your roof. Second of all, trim back any tall trees near your home, especially if any branches are hanging over your house. These branches can sway or even fall during a severe storm and damage your roof. Third, keep your gutters clear of debris. Healthy shingles will shed water, but that water still needs a place to go.

Finally, keep a close eye on your roof. This is probably the best way to get the most out of your asphalt shingles and protect your home from damage. You should be able to see any balding or damaged shingles on your roof if you look at it from the ground with a pair of binoculars, but the best way to know if you're losing granules is to look at your gutters and your downspouts. Granules in your gutters is usually a clear sign that they're eroding from your roof. Watching for this is especially important if your roof is over 20 years old or if you've recently been hit by severe weather. If you don't see any granules in your gutters but are still concerned about the state of your roof, schedule a roof inspection with a contractor. Roofing is dangerous work that should only be left to professionals, so don't climb onto your roof yourself to check things out.

When to Call a Roofing Professional

Seeing balding shingles and granules in your gutter is a sign that your roof is damaged and in need of repair, if not a replacement. If you see this sign of disrepair, contact H&R Roofing. H&R Roofing is a family-owned and operated company that serves homeowners in Rhode Island and Massachusetts, and we will be happy to take a look at your roof and make any necessary repairs. For more information about our services contact us today.

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