Asphalt shingles are one of the most popular roofing materials. However, incorrect installation processes could lead to various issues, including premature roof failure.

In this article, we will uncover the significance of the right installation methods and highlight the seven all-too-common mistakes made during asphalt shingle installation.

The Importance of Proper Asphalt Shingle Installation

Proper asphalt shingle installation is key for preserving the longevity and performance of a roof, as it protects a structure from water infiltration and weather-related damage. Correct installation begins with a clean, dry, and flat deck, followed by the application of an appropriate underlayment to guard against leaks. Shingles must then be laid down starting from the roof’s edge, with each course overlapping the one beneath it according to the manufacturer’s specifications to make a watertight seal.

Precise nailing—typically four nails per standard shingle, placed in the nail strip area—is essential to prevent blow-offs and shingle shifting due to wind uplift. In regions susceptible to high winds or ice damming, special attention must be given to the starter strip and ridge cap shingles, which should be secured with additional nails and may require the application of sealant for enhanced protection.

Adequate ventilation should also be installed to avoid heat and moisture buildup that can prematurely degrade shingles. Failure to adhere to these practices can lead to early roof failure, costly repairs, or complete replacement, as improperly installed shingles may void manufacturer warranties and fail to meet building codes. For example, a common error, such as placing nails too high on the shingle, can lead to slippage and exposure of the nail heads, creating entry points for water.

Top 7 Mistakes Made in Asphalt Shingle Installation

1. Inadequate deck preparation

Before laying shingles, the roof deck must be meticulously inspected and prepared. It should be free of old nails and debris, and any damaged plywood should be replaced. A common oversight is neglecting to re-secure loose decking boards, which can lead to uneven shingle application and a bumpy roof appearance. To build a solid base for shingle installation, use a flat bar to check for raised nails and re-nail any loose boards with 8-d ring-shank nails for a firm hold.

2. Incorrect underlayment application

The underlayment acts as a secondary barrier against water infiltration. One rare piece of advice is to consider the local climate when choosing an underlayment; in colder regions, a waterproof membrane at the eaves can prevent ice dam leaks. Make sure the underlayment is flat and properly overlapped, with at least a 2-inch horizontal and 4-inch vertical overlap. Avoid wrinkling, which can telegraph through the shingles and affect water-shedding capabilities.

3. Poor shingle alignment

Starting the first course of shingles with an uneven line can lead to a visibly crooked roof edge. To avoid this, snap a horizontal chalk line at the bottom edge of the roof as a guide. Snap vertical chalk lines every 6 to 10 feet to serve as guides for keeping shingle rows straight as you work up the roof.

4. Nailing mistakes

Nails should penetrate the decking by at least 3/4 inch or go through it completely if the deck is less than 3/4 inch thick. Nailing too high above the shingle’s nailing strip or underdriving or overdriving nails can compromise the roof’s integrity and make it prone to wind uplift. Use a nail gun with an adjustable depth setting to maintain consistent nail depth, and always check periodically by hand that the nails are flush with the surface of the shingle.

5. Inadequate sealing at roof penetrations and edges

Roof penetrations, such as vents and chimneys, require careful flashing and sealing to prevent leaks. Use proper step flashing techniques, weaving each piece with the shingles as you ascend the roof. At the edges, seal down the tabs of the first and last shingles on each row with roofing cement to secure them against wind uplift.

6. Overlooking attic ventilation

Proper attic ventilation is rarely mentioned yet is vital in preventing heat and moisture buildup that can damage roofs from within. When installing a new roof, assess the current attic ventilation and upgrade it if necessary. This includes ensuring there’s a balanced system of intake vents at the eaves or soffits and exhaust vents at or near the ridge.

7. Forgetting about manufacturer’s instructions and local building codes

Every shingle brand has specific installation instructions that must be followed to honor the warranty; ignoring these details can result in an improperly installed roof. Building codes can vary by region, especially concerning wind resistance requirements or fire ratings. Always consult the manufacturer’s guidelines and local codes before beginning installation to check for compliance and maintain warranty coverage.

An Overview of Asphalt Shingles

Asphalt shingles are the most popular roofing material in North America due to their cost-effectiveness, durability, and ease of installation. They consist of a fiberglass or organic mat coated with asphalt and topped with ceramic granules that protect against UV rays and give color to the shingles.

There are, primarily, three types: 3-tab shingles, which are budget-friendly and have a uniform appearance; architectural (or dimensional) shingles, which are thicker, provide a textured look, and offer better wind resistance; and luxury shingles, which mimic the appearance of natural slate or cedar shakes and provide the highest level of aesthetics and durability.

Asphalt shingles are designed to last between 15 and 30 years, depending on the quality and type, with warranties often reflecting this lifespan. They can also feature specialized properties like algae resistance or improved impact resistance for hail-prone areas. While installation is relatively straightforward, it requires careful attention to detail, such as proper nailing and flashing around roof penetrations to prevent leaks and hold onto the roof’s longevity.

Recognizing a Poorly Installed Asphalt Shingle Rooftop

Recognizing a poorly installed asphalt shingle rooftop involves identifying telltale signs of subpar workmanship and material handling, such as uneven or misaligned shingle rows that betray a lack of proper layout techniques and shingles with exposed nail heads, which can lead to leaks and are indicative of improper nailing. Irregular shingle overhangs at the roof’s edge may suggest inaccurate trimming that can leave the roof vulnerable to wind damage.

Curling, buckling, or blistering shingles might reveal inadequate attic ventilation, causing heat buildup that prematurely ages the roof. Inadequate or missing flashing around roof penetrations, valleys, and eaves can also be a red flag, as these are critical areas for water intrusion. Sparse granule coverage on new shingles may point to rough handling during installation, compromising their protective function.

Finally, visible signs of leaks or water damage in the attic or on ceilings inside the home are strong indicators that the roof may not have been properly sealed during installation.

The Consequences of Incorrect Shingle Installation

• Premature Roof Failure: Incorrect shingle installation can lead to early deterioration of the roof system. For instance, improper nail placement can cause shingles to become loose and detach, exposing the underlayment and roof deck to the elements and potentially leading to a complete roof failure far earlier than the expected lifespan of the materials.
• Increased Repair Costs: A poorly installed roof often requires frequent repairs. For example, shingles that are not properly overlapped or sealed may blow off during a storm, necessitating immediate repair to prevent interior water damage.
• Voided Warranty: Manufacturers provide warranties based on the correct installation methods. If shingles are not installed according to the manufacturer’s guidelines, such as by using fewer nails than recommended, the warranty may be voided, leaving the homeowner without recourse for defective shingles.
• Reduced Energy Efficiency: A roof installed without proper ventilation can trap heat in the attic, increasing cooling costs. An example is failing to install adequate ridge or soffit vents, resulting in a heat buildup that forces air conditioning systems to work harder.
• Water Damage and Mold Growth: Without proper sealing and flashing around roof penetrations and valleys, water can seep in, leading to mold and rot. An example is skylights or chimney bases where flashing is not integrated with the shingle layout correctly, causing leaks that go unnoticed until significant damage has occurred.
• Decreased Home Value: A roof with visible installation flaws can deter potential buyers due to the anticipated costs of fixing or replacing the roof. A home inspector might note curled or buckling shingles, signaling neglect or poor workmanship and impacting the overall valuation of the property.
• Safety Hazards: Incorrectly installed shingles create risks during high winds or storms; for example, a section of the roof might collapse if the shingles were not secured properly, posing a danger to occupants and property alike.
• Non-Compliance with Building Codes: Improper installation can lead to violations of local building codes, which may result in fines or mandatory corrections. If a roof does not meet wind resistance standards due to incorrect shingle installation, it may not pass inspection, requiring costly modifications.

The Role of Underlayment in Shingle Installation

The underlayment in shingle installation is a critical component that serves as a secondary barrier against moisture, protecting the roof deck from water that can get past the shingles due to wind-driven rain or snow. Typically made from felt or synthetic materials, underlayment provides additional protection against leaks, especially in areas where water tends to collect, such as valleys and around roof penetrations.

For example, in valleys where two roof planes meet, an extra layer of underlayment is often applied before shingle installation to prevent water infiltration. Underlayment aids in protecting the deck during installation, offers some degree of temporary protection in the event that bad weather delays the project, and can raise the roofing system’s overall fire rating.

Furthermore, in regions with severe weather conditions, specialized products like rubberized asphalt underlayments offer enhanced protection against ice dams and wind uplift, ensuring the roof’s integrity and longevity.

The Perils of Incorrect Nailing Technique

• Shingle Blow-Offs: Incorrect nailing technique, such as placing nails too high on the shingle or not using enough nails, can result in weak spots that make shingles susceptible to being blown off by high winds. This can leave the roof deck exposed and vulnerable to the elements.
• Water Infiltration: Nails that miss the framing members or are not driven straight can compromise the seal around the nail, allowing water to penetrate the roof. For example, angling a nail incorrectly can create a pathway for water to enter and potentially lead to leaks and water damage.
• Decreased Lifespan of Shingles: Nails that are overdriven can cut into the shingle mat, or underdriven nails can create raised areas that disrupt water flow on the roof surface. Both scenarios can lead to premature wear and a reduced lifespan of the shingles.
• Roof Deck Damage: Improper nailing can also cause physical damage to the roof deck itself. For instance, overdriving nails can splinter the wood decking, weakening its structural integrity and making it less capable of securely holding the nails.
• Compromised Wind Resistance: Shingles that are not properly nailed may not perform to their wind resistance rating. In areas prone to high winds, this could lead to widespread shingle loss during a severe weather event.
• Warranty Issues: Many shingle warranties require specific nailing techniques; failure to adhere to these guidelines can void the warranty. An example would be using fewer nails than the manufacturer’s recommendation or using the wrong type of nails, which could negate warranty coverage for any resulting damage.
• Increased Maintenance Costs: Roofs with poorly nailed shingles often require more maintenance over time due to issues like loose or missing shingles. Homeowners may find themselves regularly paying for repairs that could have been avoided with proper nailing techniques.

Challenges in Installing Shingles on Low-Slope Roofs

• Enhanced Risk of Water Penetration: Low-slope roofs do not shed water as quickly as steeper roofs, increasing the likelihood of water infiltration. Special care must be taken, such as employing a double-layer of underlayment or using self-adhering membranes to create a more impermeable barrier.
• Proper Shingle Selection: Not all shingles are suitable for low-slope applications. Manufacturers often specify a minimum slope for their products, and ignoring this can lead to shingle failures. For example, traditional 3-tab shingles may not provide adequate protection on slopes less than 2:12 without additional underlayment considerations.
• Increased Importance of Underlayment: Given the propensity for water accumulation, the role of the underlayment is even more critical on a low-slope roof. It may be necessary to use high-quality, waterproof underlayments rather than standard felt to give adequate protection.
• Difficulty in Achieving a Watertight Seal: Shingles rely on gravity to help seal the adhesive strip on each shingle to the one beneath it. On a low-slope roof, there is less gravitational force, so alternative methods, such as manually sealing each shingle with roofing cement, might be required.
• Ventilation Challenges: Proper ventilation is more difficult to achieve on low-slope roofs, as there is less vertical space for air to flow naturally. This requires careful planning to install sufficient intake and exhaust vents to prevent heat and moisture buildup that can damage both shingles and the underlying structure.
• Increased Labor Intensity: Installing shingles on a low-slope roof often requires more time and precision, as the margin for error is smaller. For example, overlapping courses need to be carefully measured and aligned to prevent leaks, making the process more labor-intensive compared to steeper roofs.
• Potential for Ponding Water: Low-slope roofs are prone to ponding water, which can lead to increased wear on the shingles and a greater likelihood of leaks. Designing the roof with tapered insulation or incorporating additional drainage points can help mitigate this issue.

The Correlation between Shingle Overhang and Leaks

The correlation between shingle overhang and leaks is significant, as improper overhang can either expose the roof edge to wind-driven rain or cause water to wick back beneath the shingles, leading to leaks.

The ideal overhang distance for asphalt shingles at the roof’s edge is typically between 1/4 inch and 3/4 inch; too little overhang can cause water to seep into the fascia or roof decking, while too much overhang can leave shingles vulnerable to lifting by strong winds or bending downward over time. This incorrectly directed water flow can cause damage to the underlying roof structure and lead to rot or mold growth.

For instance, in the case of gutters, inadequate shingle overhang may result in water bypassing the gutter system entirely, flowing down the fascia boards and potentially into the home’s foundation, while excessive overhang into the gutter can contribute to ice damming and exacerbated wear from weather conditions.

The Importance of Proper Venting in Shingle Roofs

Proper venting in shingle roofs is crucial for regulating attic temperature and moisture levels, which, if left unchecked, can lead to a host of problems affecting the longevity and performance of the roof. Adequate ventilation helps to expel hot air during the summer, reducing the heat load on the shingles and preventing premature aging or warping.

In colder climates, it minimizes the risk of ice dam formation by maintaining a cool roof surface, thereby preventing meltwater from refreezing at the eaves. It also allows moist air from daily activities such as cooking or showering to escape, thus averting condensation that can lead to wood rot, mold growth, and insulation damage. For example, installing a balanced system with soffit vents for air intake and ridge or turbine vents for exhaust provides continuous airflow along the underside of the roof deck.

This kind of system not only protects the shingle roof but also contributes to more consistent indoor temperatures and energy efficiency throughout the home.

Can Poor Installation Affect Shingle Warranties?

Yes, poor installation can significantly affect shingle warranties; manufacturers’ warranties often explicitly condition coverage on adherence to specific installation guidelines, and deviations from these instructions can void the warranty. For example, if shingles are improperly nailed or if the correct underlayment is not used, any resulting damage might not be covered.

Manufacturers stipulate the methods and materials to be used during installation, including the type of fasteners, the placement of nails, and the number of nails per shingle, as well as the proper alignment and sealing of shingles. Should issues arise due to improper installation, such as premature shingle failure or leaks, homeowners may find their warranty claims denied, leaving them responsible for repair or replacement costs that might have otherwise been covered.

Therefore, ensuring that roofing contractors follow the manufacturer’s installation requirements is crucial for maintaining warranty protection.

Hiring Professionals: Mitigating Shingle Installation Errors

Hiring professional roofing contractors is a key step in mitigating shingle installation errors, as experienced professionals possess the knowledge and skills necessary to adhere to best practices and manufacturer guidelines. By utilizing our website directory, Big Home Projects, homeowners can connect with reputable roofing experts who have a track record of quality workmanship.

These professionals make sure shingles are properly aligned, nailed, and sealed, and that the roof system is appropriately ventilated. They can also navigate complex aspects of installation, such as integrating flashing around chimneys, vents, and valleys to prevent leaks. Moreover, professional installers are typically well-versed in local building codes and can make sure the roof installation complies with regional regulations, thus avoiding costly fines or mandatory corrections.

By choosing a contractor from Big Home Projects, homeowners gain peace of mind knowing that their roof installation is performed correctly, which can extend the life of their roof and maintain the validity of their shingle warranties.