Asphalt shingles are the most common roofing material in the United States, covering an estimated 80% of American homes. But what exactly is asphalt shingle installation, and how does the process work? Understanding the fundamentals helps you make informed decisions about your roof.
What Are Asphalt Shingles? An asphalt shingle is a roofing material made from a fiberglass or organic mat, coated with asphalt, and topped with mineral granules. The granules protect the asphalt from UV rays and provide color. The asphalt provides waterproofing. The fiberglass mat gives the shingle its strength and fire resistance. This construction makes asphalt shingles durable, affordable, and relatively easy to install.
How Does Installation Work? Installation begins with tearing off the old roof (if applicable) down to the roof deck. The deck is inspected for damage and repaired. Then, a waterproof underlayment is laid over the deck. Metal flashing is installed at critical transition points—chimneys, skylights, valleys, and vents—to prevent leaks. Finally, the shingles are nailed down in overlapping rows, starting from the bottom edge and working upward. Each row overlaps the one below, creating a water‑shedding barrier.
Why Installation Quality Matters: Even the best shingles fail prematurely if installed incorrectly. Poor nailing, inadequate ventilation, or skipped underlayment can lead to leaks and reduced lifespan. For the costs involved, see our asphalt shingle installation cost guide. To understand the different shingle options, read types of asphalt shingles. For help selecting a professional, see how to choose a licensed asphalt shingle installer. And to understand what happens step by step, see what to expect during installation.
How Long Should It Last? A properly installed asphalt shingle roof should last 20–30 years or more. Learn about expected lifespan and warranty in our article on how long asphalt shingles last.