Roof Replacement
Roofing Layers Explained: What Goes Under an Owens Corning Roof?
The shingles are the part of a roof everyone notices, but they are only one part of the system protecting the home. A properly installed asphalt shingle roof includes the roof deck, water-protection membranes, underlayment, metal edges, flashing, starter shingles, field shingles, ridge-cap shingles, and ventilation working together.
That is why two roofs using the same Owens Corning shingle can perform very differently. The color and shingle package may look identical from the driveway, but the materials underneath, the flashing details, the ventilation, and the installation process can make a major difference.
This guide walks through the layers of an Owens Corning asphalt shingle roof from the wood deck upward and explains what each part is supposed to do.
The Quick Answer
What Are the Layers of a Roof?
A complete asphalt shingle roof commonly includes eight major parts: the roof decking, ice and water protection, synthetic underlayment, drip edge and flashing, starter shingles, field shingles, hip-and-ridge shingles, and balanced attic ventilation.
Not every component covers the entire roof. Some protect the full deck, while others protect edges, walls, valleys, penetrations, and roof peaks.
The visible shingle is only one part of a complete water-shedding and ventilation system.
Each component must overlap and connect correctly so water continues moving down and off the roof.
Removing the old roof allows damaged wood, old leaks, and weak fastening areas to be found before the new system is installed.
Table of Contents
- What makes a complete roof system?
- Seal, Defend, and Breathe
- The eight roofing layers and components
- 1. Roof decking
- 2. Ice and water protection
- 3. Synthetic underlayment
- 4. Drip edge and flashing
- 5. Starter shingles
- 6. Owens Corning Duration shingles
- 7. Hip-and-ridge shingles
- 8. Roof and attic ventilation
- Why full tear-off matters
- Roof-system layers versus shingle layers
- Why the layers matter in NEPA
- A typical Zenobi Roofing system
- Questions to ask before signing
- Frequently asked questions
What Makes a Complete Roof System?
A roof system is a group of materials installed in a planned sequence to move water away from the home, protect vulnerable areas, hold the shingles securely, and help heat and moisture escape from the attic.
Some components are visible after the job is finished. Most are not. Once the shingles are installed, homeowners cannot easily see the underlayment, ice and water membrane, nail placement, decking repairs, starter strip, or the way flashing was tied into the roof.
Those hidden details are one reason a roofing estimate should identify more than the shingle brand and color. It should explain the complete system being installed.
The Owens Corning Approach: Seal, Defend, and Breathe
Owens Corning organizes a complete roofing system around three important functions: sealing the roof deck against water, defending the home with shingles and accessories, and allowing the attic to breathe through balanced ventilation.
Seal
Ice and water protection and roof-deck underlayment help create secondary protection beneath the shingles.
Defend
Starter shingles, field shingles, and hip-and-ridge shingles form the primary weather-facing roof surface.
Breathe
Proper intake and exhaust ventilation help manage attic heat and moisture throughout the year.
The roof deck, drip edge, flashing, pipe boots, and other details support all three functions. A roof performs best when the components are treated as one connected system instead of unrelated materials.
A Roof System From the Deck Up
Here is the basic installation sequence homeowners should understand.
The Eight Layers and Components of an Owens Corning Roof
Roofing contractors often use the word “layers” as shorthand. Technically, some of the following materials cover the entire roof, while others are installed only at edges, peaks, walls, valleys, or penetrations. Together, they form the complete roof assembly.
Roof Decking
Roof decking is the wood surface attached to the rafters or trusses. It supports every material installed above it and provides the surface into which the roofing fasteners are driven.
Many Northeast Pennsylvania homes have plywood, oriented strand board, or older plank-style decking. During a full tear-off, the exposed deck can be checked for rot, delamination, large plank gaps, soft areas, old leak damage, and sections that no longer hold nails properly.
- Supports the entire roof system
- Must provide proper nail holding
- Inspected after the old roof is removed
- Damaged areas are corrected before installation continues
Ice and Water Protection
Ice and water barrier is a self-adhering membrane placed directly on the roof deck in areas where water intrusion is more likely. Unlike ordinary underlayment, it adheres to the deck and creates added protection around fasteners.
On homes in Lackawanna County, this material is especially important at the eaves because snow and freeze-thaw conditions can allow water to back up underneath the shingles. It may also be used in valleys, along rakes, around chimneys, near skylights, and at other vulnerable transitions.
- Installed directly over clean roof decking
- Helps protect against ice-related backup
- Used around valleys and penetrations
- Provides added protection in leak-prone areas
Synthetic Roof Underlayment
Synthetic underlayment covers the portions of the roof deck not protected by ice and water membrane. It serves as a secondary water-shedding layer beneath the shingles.
The underlayment is not meant to replace the shingles. Its job is to provide added protection beneath them and help keep the deck covered during installation. It must be installed with the proper overlaps, fasteners, and sequencing so water continues moving toward the edge of the roof.
- Covers the remaining exposed roof deck
- Sits beneath the field shingles
- Requires correct overlap and fastening
- Provides secondary water protection
Drip Edge, Flashing, and Pipe Boots
Drip edge is the metal installed along the roof perimeter to help direct water away from the wood deck and fascia. Flashing protects the places where the roof meets walls, chimneys, valleys, additions, skylights, and other transitions.
These details are among the most important parts of a roof because many leaks begin at a transition or penetration rather than in the open field of shingles.
- Drip edge at eaves and rakes
- Step flashing at roof-to-wall areas
- Counter flashing at masonry when needed
- Pipe boots around plumbing penetrations
Owens Corning Starter Shingles
Starter shingles are installed beneath the first visible course of shingles at the eaves and along the rakes. They help seal the lower and outside edges of the roof, where wind uplift can place additional stress on the shingle system.
A purpose-made starter product provides a consistent seal and proper positioning for the first shingle course. Starter material is not highly visible after installation, but leaving it out or installing it incorrectly can weaken the edge of the roof.
- Installed along eaves and rake edges
- Creates the first sealed shingle edge
- Supports proper first-course alignment
- Helps resist wind uplift at the perimeter
Owens Corning Duration Field Shingles
Field shingles cover the main roof surface and form the visible weather-facing portion of the system. They are installed from the lower edge upward so each course overlaps the course beneath it and sheds water toward the gutters.
Owens Corning Duration Series shingles include SureNail technology, which uses a visible reinforced nailing zone to help support consistent fastener placement and gripping power. The product still must be installed with the correct nail type, location, quantity, exposure, offset, and pattern.
- Primary visible roof surface
- Installed in overlapping courses
- SureNail reinforced nailing zone
- Available in multiple architectural colors
Owens Corning Hip-and-Ridge Shingles
Hip-and-ridge shingles are manufactured specifically for the peaks and outside angles of the roof. They finish the areas where two roof planes meet and create a cleaner, more consistent appearance than improvised cap pieces.
Products such as Owens Corning ProEdge are designed for these roof lines. Ridge-cap shingles may also be installed over a properly designed ridge vent so the peak is finished while exhaust air can still leave the attic.
- Installed along hips and roof peaks
- Designed to bend over roof angles
- Coordinates with the field-shingle color
- Can work with a properly installed ridge vent
Balanced Roof and Attic Ventilation
Ventilation is not a waterproof membrane, but it is an essential part of a complete roof system. Balanced ventilation allows outside air to enter through lower intake vents and warmer, moisture-laden air to exit through upper exhaust vents.
Ridge vent can provide exhaust ventilation when the roof design and available intake ventilation support it. Adding ridge vent without enough intake does not automatically create a balanced system, and combining several competing exhaust systems can sometimes reduce performance.
- Intake air typically enters near the lower roof edge
- Exhaust air exits near the roof peak
- Helps manage attic heat and moisture
- Must be evaluated as a balanced system
Important: Not Every Roof Uses the Exact Same Products
Roof shape, pitch, attic design, existing ventilation, valleys, chimneys, skylights, low-slope sections, local requirements, and warranty selection can all change the exact material package. The final written estimate should identify what will be used on your home.
Why Full Tear-Off Matters Before Installing the New Layers
A full tear-off removes the existing shingles and underlayment so the roof deck can be seen. Without exposing the deck, it is difficult to know whether the surface beneath the old roof is solid, damaged, uneven, or affected by old leaks.
Zenobi Roofing Inc. completes roof replacements as full tear-offs rather than cover-overs. This allows the roof to be rebuilt from a known starting point instead of placing new material over unknown conditions.
What a Tear-Off Can Reveal
- Rotten or delaminated plywood
- Soft decking that no longer holds nails correctly
- Large gaps in older plank decking
- Old chimney or sidewall flashing problems
- Previous leak damage hidden beneath the shingles
- Abandoned vents or conflicting ventilation systems
- Improper repairs covered by later roofing work
Once the deck is exposed and corrected, the new roofing layers can be installed over a clean and properly prepared surface.
Roof-System Layers Are Not the Same as Multiple Shingle Layers
Homeowners often hear the word “layers” used in two different ways. One meaning describes the different components of a complete roof system. The other describes multiple generations of shingles stacked on top of one another.
The ice and water membrane, underlayment, starter shingles, field shingles, ridge cap, flashing, and ventilation are intentional parts of one roof system. Installing a second roof over old shingles is different. That is commonly called a layover, roof-over, or cover-over.
A layover does not expose the roof deck for inspection. It can also leave old flashing, uneven shingle surfaces, ventilation problems, and hidden damage beneath the new roof. Even when a roof-over may be permitted under certain conditions, Zenobi Roofing recommends and performs full tear-off replacement.
Why Roofing Layers Matter in Northeast Pennsylvania
Roofs in Lackawanna County and surrounding Northeastern Pennsylvania communities experience snow, ice, freeze-thaw cycles, heavy rain, summer heat, wind, shaded roof areas, and temperature swings throughout the year.
Older homes may also have steep roof slopes, chimneys, dormers, porch roofs, additions, plank decking, complicated valleys, and roof-to-wall connections that require more than a basic shingle installation.
Each roof component addresses a different part of those conditions:
- Ice and water membrane protects vulnerable areas during freeze-thaw weather.
- Synthetic underlayment creates secondary protection across the deck.
- Flashing manages water at chimneys, walls, valleys, and penetrations.
- Starter shingles strengthen the exposed roof perimeter.
- Duration shingles create the primary weather-facing surface.
- Hip-and-ridge shingles protect roof peaks and outside angles.
- Balanced ventilation helps control attic heat and moisture.
What Is Included in a Typical Zenobi Roofing Replacement?
Every roof is evaluated individually, but a typical Zenobi Roofing asphalt shingle replacement may include the following materials and installation steps:
A Typical Owens Corning Duration Roof System
The exact written scope may change based on the home and roof design.
- Complete tear-off of existing roofing materials
- Inspection of exposed roof decking
- Replacement of damaged decking when needed
- Ice and water protection at required and vulnerable areas
- RhinoRoof synthetic roof underlayment
- Aluminum drip edge along the roof perimeter
- Owens Corning starter shingles
- Owens Corning Duration architectural shingles
- New pipe boots where applicable
- Step and counter flashing where included in the scope
- Lomanco roll ridge vent when appropriate
- Owens Corning hip-and-ridge shingles
- Debris removal and jobsite cleanup
- Magnetic nail cleanup around the property
A roof with skylights, chimneys, low-slope sections, unusual wall transitions, limited ventilation intake, or damaged decking may require additional details. Those conditions should be addressed before the project begins whenever they can reasonably be identified.
Questions to Ask About the Roofing Layers in Your Estimate
An estimate should make it possible to understand what is being installed underneath the shingles, not only the shingle brand and color.
Confirm whether all existing shingles and underlayment will be removed down to the deck.
Ask how the deck is inspected, documented, priced, and replaced when damage is found.
The estimate should identify the eaves and other vulnerable areas receiving protection.
Look for the specific product instead of a vague reference to roofing paper.
These should be purpose-made components, not details left unclear in the proposal.
Ask specifically about walls, chimneys, valleys, pipe boots, skylights, and additions.
A ridge vent should be considered together with the home’s available intake ventilation.
The estimate should list the exact product line rather than only saying architectural shingles.
Frequently Asked Questions About Roofing Layers
How many layers are in an asphalt shingle roof?
A complete asphalt shingle roof commonly includes eight major parts: roof decking, ice and water protection, synthetic underlayment, drip edge and flashing, starter shingles, field shingles, hip-and-ridge shingles, and ventilation. Some cover the entire roof, while others protect only specific locations.
What is directly underneath Owens Corning Duration shingles?
Duration shingles are normally installed over properly prepared roof decking covered by the required ice and water protection and roof underlayment. Starter shingles are installed at the roof perimeter, while flashing protects transitions and penetrations.
Is synthetic underlayment the same as ice and water shield?
No. Synthetic underlayment typically covers most of the roof deck as secondary protection. Ice and water membrane is self-adhering and is placed in more vulnerable areas such as eaves, valleys, and around certain roof transitions or penetrations.
Why are starter shingles needed?
Starter shingles create the first sealed edge beneath the visible shingles at the eaves and rakes. They support proper alignment and help protect roof edges where wind uplift can place added stress on the system.
Can Owens Corning shingles be installed over an existing roof?
A roof-over may be possible only under certain conditions, depending on the existing roof, manufacturer instructions, and applicable requirements. Zenobi Roofing Inc. performs full tear-offs so the deck can be inspected and the new roof can be installed over a properly prepared surface.
Does ridge ventilation count as a roofing layer?
Ridge vent is not a waterproof layer covering the roof deck, but it is an important roof-system component. When paired with adequate intake ventilation, it allows exhaust air to leave the attic near the roof peak.
What happens if damaged decking is found during tear-off?
Damaged or weak decking should be corrected before the underlayment and shingles are installed. The estimate should explain how replacement wood is priced and how the homeowner will be informed when damage is found.
Learn More About Roof Replacement
Understanding what goes underneath the shingles can make it much easier to compare roofing estimates and identify differences in materials, flashing, ventilation, decking, warranties, and cleanup.
Need an Owens Corning Roof Estimate?
Zenobi Roofing Inc. provides full tear-off roof replacement, roof repair, storm damage inspections, gutter service, and low-slope roofing service throughout Lackawanna County and surrounding Northeastern Pennsylvania communities.
We provide detailed, easy-to-follow estimates so you can see the materials and installation details included in your roof system.