When people imagine a roof, the first thing that comes to mind is often just the shingles—those flat, overlapping pieces that give a roof its color and shape. But a roof is much more than what meets the eye. Beneath those visible materials lies a complete system, each layer serving a unique and essential purpose in protecting your home from weather, water, and time.
Whether you're planning to replace your roof, build a new home, or just want to understand how everything works together, knowing the materials involved in a complete roofing system can help you make more informed decisions and avoid surprises.
In this guide, we'll walk through every major component you'll need to build or replace a full roofing system—starting from the foundation up. We’ll cover everything from the base decking to ventilation and finishing touches, showing how each element works together to create a strong, weather-resistant roof.
The first layer of any roofing system is the roof decking, sometimes referred to as sheathing. This is the structural base that supports all the layers above it. Most often made from plywood or oriented strand board (OSB), the decking is nailed or screwed into the roof's trusses or rafters. Everything else, from underlayment to shingles, is installed on top of it.
While most roof decks last for decades, they can rot or weaken due to moisture infiltration. This is why many roof replacements include partial deck repairs, especially if leaks were present. A solid, dry deck is essential to ensure all other roofing components perform as intended.
Directly above the decking lies the underlayment. It acts as a secondary moisture barrier, protecting your home in case water seeps through the shingles. There are two primary types of underlayment: felt paper, which is more traditional, and synthetic underlayment, which offers improved strength, flexibility, and resistance to tearing.
Some areas also require ice and water shield, a special type of self-adhering underlayment that provides added protection in vulnerable areas like valleys, eaves, and around roof penetrations. Made from rubberized asphalt, ice and water shield is particularly effective in colder climates or regions prone to heavy rain.
Often overlooked but incredibly important, the drip edge is a thin strip of metal installed along the edges of the roof. It helps guide water away from the fascia and into the gutters, preventing water from seeping under the shingles or rotting the wooden edges of your roof. Proper drip edge installation can extend the life of both your roof and your home’s siding.
Asphalt shingles are the most visible component of your roof—and also its first line of defense against the elements. There are several types of asphalt shingles, including 3-tab, architectural, and luxury shingles. Each has different lifespans, aesthetics, and resistance levels to wind and weather.
These shingles are made from a fiberglass mat coated in asphalt and topped with mineral granules for UV protection. They're durable, cost-effective, and come in a variety of colors and styles, making them a top choice for homeowners across North America.
Before the main shingles are installed, a row of starter shingles is applied along the eaves and rake edges. These help the first course of shingles bond properly and seal out wind and water at the vulnerable edges.
At the highest point of your roof—the ridge—you’ll find ridge cap shingles. These specially shaped shingles are thicker and pre-bent to fit over the roof’s peak, sealing the joint where two roof slopes meet and finishing the system in a way that looks good and performs even better.
No matter how well a roof is designed, there will always be areas that need additional sealing—such as where chimneys, skylights, or walls intersect with the roof. This is where flashing comes in. Typically made of thin metal (like aluminum or galvanized steel), flashing is installed to direct water away from seams and prevent leaks in these vulnerable areas.
Proper flashing installation is crucial. Poorly installed flashing is one of the most common sources of roof leaks, particularly around chimneys and roof valleys.
Another area that requires extra attention is where pipes and vents come through the roof. These are sealed using pipe boots, which are rubber or metal covers designed to create a watertight seal around the base of the pipes. Over time, these boots can crack or deteriorate, so they’re often replaced during a full roof replacement.
Proper ventilation is essential to any roofing system. Without it, heat and moisture can build up in the attic, leading to problems like mold, warped decking, and shortened shingle life. Ventilation systems can include:
Each offers a way to circulate air and maintain a healthy attic environment. Balanced ventilation extends the life of your roof, reduces cooling costs, and can even help protect your insulation and framing.
While technically not a part of the roof itself, gutters play a crucial role in maintaining roof health. By catching and redirecting rainwater away from your home's foundation, they prevent water from backing up onto the roof deck and causing rot, leaks, or mold. If your gutters are clogged or improperly installed, it can quickly lead to damage that affects your entire roofing system.
Lastly, don’t forget about the fasteners—small but mighty components that hold everything together. Most asphalt shingle roofs use galvanized roofing nails that resist rust and corrosion. Using the right type and size of nail ensures your shingles stay in place through storms, wind, and everyday wear.
Different types of fasteners are also used for flashing, drip edge, and underlayment, so your contractor must use products that match the materials and local code requirements.
A roof is more than just a layer of shingles. It’s an integrated system of materials, each serving a critical purpose to keep your home dry, safe, and energy-efficient. Cutting corners on any one of these elements can compromise the whole structure. Whether you're hiring a contractor or just learning about the process, understanding each layer will help you ask smarter questions, recognize quality work, and ultimately protect your investment.
At Hover, we help homeowners visualize, estimate, and plan their roofing projects with precision. Whether you're replacing your roof or exploring new materials, understanding what makes up a complete roofing system is the first step in making confident, informed decisions.
Have questions about your roofing project or want to explore roofing materials virtually? With Hover, you’re in control—no ladders, no guesswork, just accurate models and expert insights, right from your smartphone.