Introduction
A roof replacement involves nine core materials, and each one has a specific function that helps prevent common roofing problems.
In this article you’ll learn how to assess material roles, spot signs of wear, and approach decisions on selection, installation considerations, and budgeting.
Key takeaways
- Roof decking: plywood or plank decking affects substrate stability and fastener integrity.
- Drip edge provides metal protection along eaves and rakes against water intrusion.
- Underlayment choice matters: felt offers breathability; synthetic resists tearing longer.
- Ice and water shield targets vulnerable areas to prevent leaks at hips, ridges, and penetrations.
- Flashing and pipe boots direct water away from penetrations, preventing joint leaks.
- Ventilation: balanced intake and exhaust vents reduce moisture, heat buildup, and shingle deterioration.
Table of Contents
- Introduction
- Key takeaways
- Roof decking (sheathing): plywood vs. plank decking
- Drip edge: protection at eaves and rakes
- Underlayment (felt vs. synthetic)
- Ice and water shield: targeted waterproofing
- Roof flashing and pipe boots: directing water away from penetrations
- Starter shingles, main roofing material, and ridge capping
- Roof ventilation (intake and exhaust vents)
- Accessories, flashing alternatives, and specialty components
- Conclusion
- FAQ
Roof decking (sheathing): plywood vs. plank decking
Roof decking, or sheathing, is the structural substrate that supports the roof system. It transfers load from the roofing material to the framing and helps define venting and insulation interactions. The decking also plays a key role in how underlayment sits against the surface and how edge details are managed at the eaves and rakes.
Compare plywood/sheet decking with plank decking by looking at surface rigidity, spacing, and thickness, along with typical spans. Plank decks can present less planarity and require careful fastener planning to keep laps tight. Structural implications include load-bearing capacity, nailing patterns, and how weathered wood may affect leaks or wind uplift. Choose decking type based on roof pitch, climate, and existing framing, and be prepared to consult a structural pro if there are red flags.
Plywood/Sheet Decking—Benefits and Common Issues
Plywood’s the old standby for roof decking. It’s strong, affordable, and easy to find.
Thickness matters. Typical ranges are 7/16″ to 1/2″. Thicker isn’t always better—it can warp or crack under load. Check manufacturer specs for your chosen thickness.
Support’s key. Plywood spans joists every 16″ to 24″. Less than that, it may sag or fail. More, and you’re wasting money. Check your rafter spacing before buying.
Common failures? Rot happens if water sits on the decking. Fastener pull-out’s another issue. Nails can pop up in high winds. Screws hold better but can still back out. Inspect for these during replacement.
Plank Decking—When It’s Used and How to Inspect
Plank decking, also known as board sheathing, is typically used on lower-pitched roofs where the load from snow or rain isn’t too heavy. It’s cheaper than plywood but has its own quirks.
Gaps are normal, unlike plywood. They help with drainage and ventilation. But check for excessive gaps, which can compromise your roof’s integrity. If you find any, overlay or resheath to prevent issues later on.
To inspect plank decking, look for these signs of trouble:
- Cracks or splits in the boards. These can let water in and lead to leaks.
- Warping or cupping. This means the boards aren’t flat anymore, which can cause problems with your roofing material.
- Nails popping up. If nails are coming out of the boards, it’s a sign that the decking is failing.
If you spot any of these issues, don’t just repair. Check with your local building department to see if you need to resheath or overlay. Better safe than sorry when it comes to your roof.
Drip edge: protection at eaves and rakes
Drip edge is a metal edging installed at the roof perimeter to direct water into the gutter and away from the fascia. It protects the eaves and rakes from water infiltration and helps keep the underlying wood dry. Proper placement also supports the underlayment and flashing details at the edge.
Install locations include the bottom edge (eaves) and the side edges (rakes). Material options vary, with galvanized steel, aluminum, and copper common choices that balance durability and appearance. Typical missteps involve gaps, misalignment, or improper overlap with underlayment and flashing, so verify installation details and inspect alignment with gutters and roof edges during a replacement.
Installation best practices and common mistakes
Here are some key aspects to consider when installing drip edge, along with common mistakes to avoid.
- Metal type: Choose the right metal for your roof. Galvanized steel is durable but heavy; aluminum is lighter and more affordable; copper is premium but expensive.
- Overhangs: Ensure drip edge extends beyond fascia to direct water into gutters, not behind them.
- Nailing sequence: Nail through drip edge first, then underlayment, to keep nails from piercing underlayment and causing leaks.
- Improper overlapping: Overlap drip edges at eaves and rakes by 2-3 inches to prevent water tracking behind gutters. Avoid gaps or misalignment.
Proper installation ensures water is directed away from the roof edge, protecting fascia, soffit, and decking.
Visual checkpoints and maintenance tips
Regularly inspect your drip edge to ensure it’s functioning properly. Here’s a quick checklist:
- Rust: Check for rust, especially at corners and overlaps. Rust can cause leaks and weaken the drip edge.
- Gutter alignment: Ensure drip edge is aligned with gutters to prevent water overflows.
- Underlayment exposure: Make sure underlayment isn’t exposed at eaves or rakes, as it can degrade and cause leaks.
- Damage: Inspect for damage from animals, wind, or ice dams. Replace any damaged sections.
Quick rule: Inspect drip edge annually, before winter, and after severe weather events to ensure it’s protecting your home as intended.
Underlayment (felt vs. synthetic)
Underlayment acts as a secondary moisture barrier that protects the decking from vapor, wind-driven rain, and ice formation. It also provides a buffer between the deck and the roofing material. Whether you’re reroofing or replacing the full roof, ensure the underlayment integrates correctly with flashing and ice/water shield.
Compare asphalt-saturated felt to synthetic underlayment for durability and tear resistance. Felt has traditional use and familiar handling, while synthetic options offer better UV resistance and long-term performance in varied climates. Consider installation ease, weight, and how the pitch and ventilation affect your choice, and follow local codes and manufacturer instructions for overlaps and fasteners.
Choosing the right underlayment for your roof material
The type of underlayment you choose should complement your roofing material to ensure optimal performance and longevity. Here are some key considerations:
- Asphalt Shingles: Felt underlayment is commonly used with asphalt shingles due to its affordability and compatibility. Look for 15 lb or 30 lb felt, which indicates the weight per square foot. To avoid wrinkling, ensure proper overlap (at least 2 inches).
- Metal Roofs: Synthetic underlayment is often preferred with metal roofs due to its durability and resistance to punctures during installation. Opt for slip-resistant varieties to enhance safety. Ensure it’s compatible with your chosen metal roofing system.
- Tile Roofs: Synthetic underlayment is also ideal for tile roofs, as it provides excellent protection against moisture intrusion. Choose a product rated for high heat and UV exposure. Proper overlap (at least 4 inches) is crucial to prevent water penetration.
- Wood Shakes/Shingles: Both felt and synthetic underlayments can be used with wood shakes/shingles, but synthetics offer better durability and tear resistance. Ensure the product has good slip resistance for safety during installation. Look for products rated for high wind resistance.
- Climate Considerations: In hot climates, opt for underlayments with high UV resistance to prevent degradation. In cold climates, choose products that remain flexible in low temperatures to avoid cracking.
Installation details that affect performance
The way you install underlayment significantly impacts its ability to protect your roof. Here are some key installation details to consider:
Overlap: Proper overlap is crucial to prevent water intrusion. For felt, overlap should be at least 2 inches; for synthetics, follow the manufacturer’s recommendations, typically around 4-6 inches.
Fasteners: Use corrosion-resistant nails (galvanized or stainless steel) to secure underlayment. Avoid using staples, as they can easily pull through the material and cause leaks. Nail in the overlap area only, following a straight line about 1 inch from the top edge.
Sealing Seams: For added protection, consider sealing seam areas with roofing cement or tape. This is especially important for felt underlayment, which can absorb water and wick it along seams. Proper installation prevents blistering, water intrusion, and premature failure of the underlayment.
Ice and water shield: targeted waterproofing
An ice and water shield is a premium underlayment applied in vulnerable roof areas to prevent water intrusion from ice dams and wind-driven rain. It provides a more secure moisture barrier at transitions and penetrations. Unlike standard underlayment, it is designed to seal around edges and gaps where water could seep in.
Install where required or recommended, such as eaves, rakes, valleys, and around penetrations, following code or manufacturer guidance. It functions best when used with compatible flashing and underlayment systems, and you should inspect thickness and overlaps to ensure continuous protection over time. Remember to verify compatibility with your chosen roofing material.
Proper placement and sequencing
Ice and water shield should be placed in critical areas to prevent water intrusion. It’s usually required or recommended at:
- Eaves: Start 24″ up from the eave edge, overlapping drip edge.
- Rakes: Cover the entire rake area, extending onto the roof slope.
- Valleys: Lay strips along valley centerline, lapping shingles over it.
- Penetrations: Surround chimneys, vents, and skylights with a 3″-6″ wide strip.
Climate considerations: In freeze/thaw areas, extend shield higher up the roof (at least 24″ above expected snow line). Always integrate it with flashing for best protection.
Material types and adhesion issues
Choosing the right ice and water shield is crucial. Self-adhering membranes are popular, but they need proper installation to work effectively.
- Self-adhering: Uses adhesive backing for application. Look for ASTM D4601 rating (min. 25 lb/sq ft). Avoid if roof surface is dirty or wet.
- Asphalt-saturated: Needs separate adhesive. Slower installation but good