A Homeowner’s Guide to Roofing Layers
When most people picture a roof, they picture shingles, but shingles are only the surface of a much more complex system designed to protect your home from weather, moisture, and structural damage. Beneath that top layer is a combination of materials that work together to keep your house dry and sturdy.
If you’ve ever wondered what’s really under your shingles, or how to tell if those hidden layers need attention from a professional roofer, this article should help answer your questions.
The 9 Core Components of a Roofing System
A roof is built like a team: every component has a job, and when they work together, they provide a strong line of defense for your home. Each layer is designed to stop water from leaking into your home, resist wind, and improve structural stability. Understanding these parts makes it easier to spot issues early and know what questions to ask during roof inspections.
Let’s take a closer look at the eight key parts that make up a reliable roofing system:
1. Roof Decking (Sheathing)
At the base of your roof sits the decking, sometimes called sheathing. Decking is usually made of plywood or oriented strand board (OSB), and it’s attached directly to the rafters or trusses of your home.
It serves as the foundation of your roof, and every other material, including underlayment, shingles, and flashing is attached to it. Without decking, your roofing system can’t function properly.
Decking should only be replaced once it’s damaged. Signs of damage include sagging areas, visible rot, or “soft spots” where the wood feels spongy underfoot. Water intrusion, mold, or pests can all compromise its strength.
If your roof is being inspected, ask your contractor to check for decking damage. A healthy deck can last as long as your home with proper ventilation and care.
2. Underlayment
Underlayment lies directly on top of your roof’s decking. This layer is easy to overlook since it’s never visible once shingles are installed, but it plays an important role in keeping your home dry.
Traditional underlayment used to be made of asphalt-saturated felt (sometimes called “tar paper”). Today, synthetic underlayments are becoming the standard, offering lighter weight, tear resistance, and better water protection.
For any reason, should your roof surface crack, break, or open up, its underlayment will need to be replaced. If you live in an older home with tar paper, ask your roofer about synthetic underlayment, as it generally lasts longer and offers more protection.
3. Ice and Water Shield
Certain areas of a roof are more prone to leaks than others, like valleys where water collects, or the edges where ice can build up in winter. Your roof’s ice and water shield membrane is a peel-and-stick material that bonds directly to the decking, sealing around nails and creating a watertight layer.
Similarly to underlayment, your ice and water shield should always be replaced if your roof is damaged and needs repairs.
4. Starter Strip
At the very edges of your roof sits the starter strip, a specialized row of shingles that look similar to shingles but are specially designed to anchor the first visible row.
Starter strips provide an adhesive seal to anchor the first row of shingles, preventing wind uplift. Without them, wind can get under the edge shingles and peel them back, and once that happens, water intrusion is almost guaranteed.
Note that not all contractors use starter strips, and prefer to cut regular shingles instead. While that can work, dedicated starter strips provide better adhesion and wind resistance, so let your roofer know if you’re interested in installing true starter strips.
5. Shingles
Shingles protect your home from rain, snow, UV rays, and wind. They come in different styles and materials, including wood, slate, tile, and metal, but the most popular shingle material is asphalt.
Depending on material type, shingles typically last 20-30 years, but they can age, curl, and crack over time. Keep an eye out for shingle granules in your gutters. Excessive shedding often means your shingles may near the end of their lifespan.
6. Flashing
Flashing is made of thin pieces of metal, usually aluminum, galvanized steel, or copper, installed around roof features where water naturally collects or where two surfaces meet. You’ll find it around chimneys, skylights, vents, valleys, and along walls.
Flashing directs water away from seams and vulnerable joints so it doesn’t seep into your home. Even the most durable shingles can’t stop leaks on their own without properly installed flashing.
While it doesn’t always need to be replaced during roof work, flashing should be inspected closely. Rust, bending, gaps, or deteriorated sealant are clear signs it needs attention. Homeowners usually choose to replace flashing during major roof updates for added peace of mind.
7. Drip Edge
Installed along the edges where the roof meets the gutters, the drip edge guides rainwater away from the fascia and into the gutter system where it belongs. Without it, water can sneak under the shingles, soak the wood, and cause rot over time.
While the drip edge doesn’t draw attention the way shingles do, it goes a long way in helping your roof last longer. In fact, many building codes now require it because of the protection it provides.
During roof inspections, your roofer should ensure that the drip edge is firmly in place and not bent, rusted, or missing sections. It’s a small component, but if it’s damaged or skipped altogether, it can lead to major roof repairs.
8. Ventilation
A good roof system lets air ventilate through your attic. Ridge vents, soffit vents, and gable vents work together to create airflow, allowing hot, moist air to escape and fresh air to circulate.
Without proper ventilation, your attic can overheat in the summer and freeze in the winter. Extreme temperature swings can increase your energy bills, and cause shingles to wear out faster, encourage mold growth, and the formation of ice dams.
Ventilation systems don’t usually need frequent replacement, but they should be checked during roof inspections. It’s worth the time to make sure they’re clear, unblocked, and functioning properly.
9. Pipe Boot
A pipe boot is a specially designed flashing that seals the area around vent pipes. This keeps water from sliding down the outside of the pipe and into your home.
Most pipe boots are made of rubber, metal, or a combination of both. Over time, the rubber portion can crack, dry out, or pull away from the pipe, especially after years of sun exposure. When that happens, even a light rain can find its way inside.
Replacing a pipe boot is a relatively simple repair compared to other roofing components, but it’s not something to ignore. During inspections, always have your roofer check the condition of the boots.
Why Every Homeowner Should Know Their Roof Layers
Even if you’re not planning a roof project right now, understanding what’s under your shingles gives you a major advantage as a homeowner. Your roof is one of the biggest investments in your home. Being familiar with its layers helps you make informed decisions instead of just nodding along when a contractor rattles off roofing jargon.
When you know what each part does, you can:
- Spot trouble before it spreads. A small leak around flashing or a cracked pipe boot can be easy to fix if caught early. Left unnoticed, those same issues can lead to costly water damage inside your home.
- Ask sharper questions during inspections. Instead of just asking if you need a “new roof,” you’ll know to ask about the condition of the underlayment, ventilation, or drip edge. That kind of knowledge keeps contractors accountable and ensures you’re getting what you pay for.
- Save money by avoiding unnecessary replacements. Not every layer needs to be swapped out during roof work. For example, decking only gets replaced if it’s damaged. Knowing the difference helps you avoid paying for work that isn’t actually needed.
When every layer is in good condition and working as intended, you get a roof that looks great from the street and protects your home for decades. Being informed is the best way to make sure your roof lives up to its full potential.
Protect Your Home With Our Expert Roofing Services
At All Craftsmen Exteriors, we’ve built our reputation on honesty, quality, and craftsmanship. Our team inspects your entire roofing system to make sure every layer is doing its job.
If you’re not sure about the condition of your roof, or if you want peace of mind before the next storm season, contact us today for a free estimate and see why Minnesota homeowners trust us to keep their homes safe and sturdy.
