Installing Metal Roof Over Asphalt Shingles

Installing a metal roof over asphalt shingles presents a unique set of challenges and rewards. This process, while seemingly straightforward, requires careful planning and execution to ensure a long-lasting, weather-tight roof. From the initial assessment of the existing roof to the final installation of flashing and trim, each step demands precision and attention to detail. This guide will walk you through the entire process, providing valuable insights and practical advice to help you achieve a successful outcome.

This comprehensive guide covers all aspects of the project, from the initial inspection and removal of the old asphalt shingles to the installation of the new metal roofing system. We’ll delve into the crucial steps of roof deck preparation, ensuring a stable and level surface for optimal metal roof performance. We’ll also explore various metal roofing systems, highlighting their advantages and disadvantages to help you make informed decisions. Safety precautions will be emphasized throughout, ensuring a safe and efficient installation process.

Preliminary Assessment

A thorough preliminary assessment of the existing asphalt shingle roof is crucial before commencing the metal roof installation. This step ensures the longevity and safety of the new roof and prevents unforeseen complications during and after the installation process. A comprehensive inspection will identify potential problems that, if left unaddressed, could compromise the integrity of the new metal roof.

Roof Inspection Procedures

A systematic approach is vital for effective roof inspection. Begin by visually inspecting the entire roof surface from the ground, using binoculars if necessary, to identify any large-scale issues like significant damage or missing shingles. Then, proceed to a more detailed inspection from the roof itself, using appropriate safety measures like a harness and fall protection equipment. This detailed inspection involves carefully examining each section of the roof for signs of damage or deterioration.

Tools and Equipment for Roof Inspection

Safe and efficient roof inspection requires specific tools and equipment. These include a sturdy ladder, a safety harness with appropriate anchor points, work gloves, binoculars for initial ground-level assessment, a roofing hatchet or pry bar for gently lifting shingles to check for underlying damage, a moisture meter to detect hidden moisture problems, a camera to document findings, and a measuring tape for recording dimensions and distances. Personal protective equipment (PPE), such as safety glasses and hard hats, is also essential.

Identifying Potential Roof Issues

During the inspection, carefully look for signs of rot, leaks, and structural damage. Rot is often indicated by soft, spongy areas on the decking, discoloration, or the presence of fungal growth. Leaks can be identified by water stains on the ceiling below or by the presence of damp insulation. Structural damage may manifest as sagging rafters, cracked or broken decking, or loose flashing around chimneys and vents. Pay close attention to areas around chimneys, vents, and valleys, as these are common points of failure. For example, a missing or damaged flashing around a chimney can lead to significant water damage over time.

Roof Inspection Checklist

A comprehensive checklist is vital for documenting the findings. The checklist should include sections for each area of the roof, noting the presence or absence of damage, its severity, and its location. Specific items to include are:

• Overall condition of asphalt shingles (missing, damaged, curled, etc.)
• Condition of the underlying decking (rot, cracks, damage)
• Presence of leaks (water stains, damp insulation)
• Condition of flashing around chimneys, vents, and valleys
• Condition of the roof structure (sagging rafters, cracked decking)
• Presence of any signs of pest infestation
• Measurements of damaged areas
• Photographs or sketches of damaged areas

This documented assessment serves as a crucial reference for planning the metal roof installation and addressing any necessary repairs before the new roof is installed. It allows for accurate material estimation, appropriate labor scheduling, and ultimately, a successful and long-lasting metal roof installation.

Removal of Asphalt Shingles

Removing asphalt shingles safely and efficiently is crucial for a successful metal roof installation. This process requires careful planning and execution to minimize waste, protect the underlying roof deck, and ensure worker safety. Proper disposal of the old shingles is also essential for environmental compliance.

Safe Shingle Removal Techniques

Safe shingle removal involves prioritizing worker safety and minimizing damage to the underlying roof deck. Workers should always use appropriate safety equipment, including hard hats, safety harnesses, and fall protection systems. Shingles should be removed in a systematic manner, starting from the ridge and working down to the eaves. This prevents accidentally dislodging shingles from higher areas and ensures a controlled removal process. It is also important to maintain a clear work area to avoid tripping hazards. Using a pry bar or roofing shovel, carefully lift and remove shingles, taking care not to damage the underlying felt or roof deck.

Nail and Staple Removal Techniques

Several methods exist for removing nails and staples from the roof deck. A specialized roofing nail puller can efficiently remove nails without damaging the wood. For larger areas or stubborn nails, a magnetic nail puller attached to a power drill can expedite the process. Another effective technique involves using a pry bar to loosen nails before pulling them out manually. In cases where staples are present, a staple remover or a combination of a pry bar and hammer can be used for removal. It’s important to thoroughly inspect the roof deck after nail and staple removal to ensure all fasteners are removed to prevent damage to the new metal roofing system.

Asphalt Shingle Disposal

Proper disposal of old asphalt shingles is crucial for environmental responsibility. Many municipalities have specific regulations regarding construction and demolition waste. Check local regulations to understand the acceptable disposal methods. Options typically include taking the shingles to a designated landfill or recycling center that accepts asphalt shingles. Some regions offer shingle recycling programs that repurpose the material for other applications. Always ensure that disposal is conducted in accordance with all applicable environmental laws and regulations. For larger projects, consider hiring a licensed waste removal company experienced in handling roofing materials.

Step-by-Step Shingle Removal Guide

Step	Description	Image Description	Potential Hazards
1. Preparation	Inspect the roof, gather necessary tools (pry bar, roofing shovel, nail puller, safety harness, etc.), and clear the work area.	A worker inspecting the roof, wearing a hard hat and safety harness, with tools laid out nearby. The image shows a clear workspace free of obstructions.	Falls from height, cuts from sharp shingle edges.
2. Ridge Removal	Begin removing shingles from the ridge, carefully prying them up and removing nails.	Close-up view of a worker carefully prying up a shingle from the roof ridge, using a pry bar. The image highlights the methodical approach.	Falls from height, damage to underlying felt.
3. Shingle Removal (Rows)	Work your way down the roof in rows, removing shingles and nails systematically.	A wider shot showing a section of roof with shingles partially removed, illustrating the systematic row-by-row approach.	Falls from height, cuts from sharp shingle edges, slips on loose materials.
4. Nail/Staple Removal	Remove all nails and staples from the roof deck, using appropriate tools.	A close-up view of a worker using a nail puller to remove nails from the roof deck. The image highlights careful and thorough removal.	Damage to the roof deck, injury from using tools improperly.
5. Debris Removal	Carefully remove all debris from the roof, ensuring a clean surface for the new metal roofing.	A clean roof deck with all shingles and debris removed. The image showcases a properly prepared surface for installation.	Falls from height, slips on loose materials.

Roof Deck Preparation

A properly prepared roof deck is paramount for a long-lasting and leak-free metal roof. Neglecting this crucial step can lead to future problems, including premature failure of the metal roofing system and potential water damage to the building’s structure. Thorough cleaning and preparation ensure the metal roofing system adheres correctly and performs optimally.

The condition of the existing roof deck significantly impacts the success of the metal roof installation. This phase involves inspecting for damage, repairing or replacing compromised areas, and ensuring a consistently smooth and level surface for optimal metal panel installation. Any imperfections left unaddressed will be transferred to the new metal roofing system, compromising its aesthetic appeal and structural integrity.

Roof Deck Cleaning

Cleaning the roof deck removes debris, loose asphalt granules, and any other contaminants that could interfere with the adhesion of the new metal roofing system. This process typically involves using a stiff-bristled broom or a pressure washer to thoroughly remove all loose materials. Careful attention should be paid to removing any standing water or accumulated debris in low-lying areas. A clean surface promotes better adhesion and ensures the longevity of the metal roof. For stubborn debris, a scraper can be used cautiously to avoid damaging the underlying plywood.

Damaged Roof Deck Repair and Replacement

Damaged sections of the roof deck, such as rotted plywood or areas with significant water damage, must be repaired or replaced before installing the new metal roof. This typically involves cutting out the damaged sections and replacing them with new, appropriately sized plywood sheets. The new plywood should be securely fastened using corrosion-resistant nails or screws, ensuring proper spacing and alignment to prevent warping. For larger areas of damage, it may be necessary to replace entire sections of the roof deck. All repairs should be made using materials that are compatible with the existing structure and the new metal roofing system.

Addressing Unevenness and Imperfections

Unevenness in the roof deck can lead to problems with the metal roofing system, including uneven panel alignment and potential stress points. To address minor imperfections, wood shims can be used to level the surface. These are small pieces of wood placed strategically beneath the plywood to create a smooth, even surface. For more significant unevenness, a layer of self-leveling compound may be necessary. This compound is poured over the existing deck and allowed to dry, creating a smooth and level surface for the metal panels. The self-leveling compound should be selected based on its compatibility with the plywood and the overall roofing system. The goal is to achieve a consistently level surface for the installation of the metal roofing panels, thereby preventing any stress or unevenness from transferring to the final roof.

Metal Roof Installation

Installing a metal roof over existing asphalt shingles requires careful planning and execution to ensure a long-lasting, weather-resistant roof. This process involves several key steps, from panel selection and underlayment installation to securing the panels and creating weather-tight seals. Proper installation techniques are crucial for maximizing the lifespan and performance of the new metal roofing system.

Metal Roofing Systems Suitable for Overlay

Several metal roofing systems are suitable for overlaying asphalt shingles. The choice depends on factors such as budget, aesthetic preferences, and the specific characteristics of the existing roof. Common options include standing seam metal roofing, corrugated metal roofing, and metal shingle roofing. Standing seam systems, known for their sleek appearance and superior weather resistance, often involve interlocking panels that create a nearly seamless roof surface. Corrugated metal roofing, a more economical choice, offers a classic, ribbed profile. Metal shingle roofing mimics the look of traditional asphalt shingles but provides the durability and longevity of metal. Each system presents unique installation challenges and advantages regarding weight, ease of installation, and overall cost. For instance, standing seam systems, while more expensive, typically require less fastening and are known for their exceptional longevity, whereas corrugated panels might be easier to install but may require more frequent maintenance.

Underlayment and its Importance

Using an appropriate underlayment is crucial for protecting the roof deck and ensuring the longevity of the metal roof. Underlayment acts as a secondary water barrier, preventing moisture from penetrating the roof deck even if the metal roofing system is compromised. This is especially important when installing a metal roof over existing asphalt shingles, as the underlying shingles may be degraded or damaged. Several types of underlayment exist, including synthetic underlayments and felt underlayments. Synthetic underlayments are typically more durable, water-resistant, and easier to work with than felt underlayments. A properly installed underlayment significantly contributes to the overall performance and lifespan of the roofing system, protecting the building from water damage and potential structural issues. For example, a high-quality synthetic underlayment can withstand strong winds and heavy rain better than traditional felt, preventing leaks and ensuring the longevity of the roof.

Fastening Metal Roofing Panels

Secure and weather-tight fastening of metal roofing panels is paramount for the roof’s performance. The specific fastening method will vary depending on the type of metal roofing system chosen. Generally, self-tapping screws designed for metal roofing are used, with the screws spaced according to the manufacturer’s specifications. It’s crucial to use screws that are long enough to penetrate the metal panels and the underlying sheathing without piercing the roof deck completely. The screws should be driven in straight to avoid damaging the metal panels. Proper sealing around the screw heads is also essential to prevent water leakage. Butyl rubber sealant or a similar product should be applied to each screw head after installation to create a weather-tight seal. For example, in a standing seam system, the panels often interlock, requiring fewer fasteners than corrugated metal, thus reducing the potential for leaks. However, proper sealant application is still crucial for all systems to prevent water intrusion.

Flashing and Trim

Proper flashing and trim installation is crucial for a long-lasting and leak-free metal roof. These components act as barriers, preventing water from penetrating vulnerable areas around roof penetrations and edges. Careful attention to detail during this phase significantly impacts the overall performance and longevity of your new roof.

Flashing and trim are essential components in protecting your roof from water damage. Different materials offer varying degrees of durability and weather resistance, and their selection should be based on the specific needs of your roof and climate. Proper installation techniques ensure a watertight seal, preventing costly repairs down the line.

Flashing Materials and Applications

Flashing materials are selected based on their durability, corrosion resistance, and compatibility with the metal roofing system. Common materials include galvanized steel, aluminum, copper, and stainless steel. Galvanized steel is a cost-effective option, offering good corrosion resistance. Aluminum is lightweight and corrosion-resistant, making it suitable for various applications. Copper offers superior corrosion resistance and a visually appealing patina over time, while stainless steel provides exceptional durability and longevity, often preferred for high-performance systems. The choice of flashing material depends on factors such as budget, climate, and aesthetic preferences. For example, in coastal areas with high salinity, stainless steel or copper flashing might be preferred due to their superior corrosion resistance compared to galvanized steel.

Chimney Flashing Installation

Proper chimney flashing prevents water from entering the gap between the chimney and the roof. A multi-layered system is typically employed, ensuring complete water protection. Failure to install chimney flashing correctly can lead to significant water damage within the structure.

• Step 1: Install the Base Flashing: A continuous piece of flashing is installed under the shingles, extending up the chimney’s sides. It creates a watertight barrier at the base.
• Step 2: Install the Step Flashing: Individual pieces of flashing are installed vertically, overlapping each shingle course. This creates a series of steps that guide water away from the chimney.
• Step 3: Install the Cap Flashing: A piece of flashing is installed over the top of the chimney, extending down the sides. This overlaps the step flashing, completing the watertight seal.
• Step 4: Seal All Joints: All joints and overlaps should be sealed with a high-quality roofing sealant to ensure a completely waterproof system. This sealant should be compatible with both the flashing material and the metal roofing.

Vent Flashing Installation

Similar to chimney flashing, vent flashing prevents water intrusion around roof penetrations such as plumbing vents, exhaust vents, and skylights. Proper installation is critical to maintain a watertight seal around these vulnerable areas.

• Step 1: Prepare the Opening: Ensure the vent is properly sealed to the roof deck before installing flashing.
• Step 2: Install the Base Flashing: A flashing piece is placed under the vent and sealed to the roof deck.
• Step 3: Install the Cap Flashing: A flashing piece is placed over the vent, covering the base flashing and creating an overlap. Seal all seams with roofing sealant.

Trim and Edge Piece Installation

Trim pieces, such as rake edge trim, gable trim, and hip and ridge caps, provide a finished look and protect the roof edges from weather damage. Proper installation is essential for both aesthetics and functionality.

• Step 1: Measure and Cut: Accurately measure the length of each trim piece needed and cut to the appropriate size, allowing for overlaps and expansion.
• Step 2: Secure the Trim: Secure the trim pieces using appropriate fasteners, ensuring proper spacing to allow for expansion and contraction. Overlap the trim pieces appropriately, creating a watertight seal.
• Step 3: Seal Joints: Seal all joints and overlaps with roofing sealant to prevent water penetration.

Safety Precautions

Installing a metal roof over asphalt shingles is a physically demanding job requiring work at significant heights. Prioritizing safety throughout the entire process is paramount to prevent injuries and ensure a successful project. This section details crucial safety measures, appropriate personal protective equipment, safe work practices at heights, and emergency procedures.

Personal Protective Equipment (PPE)

Appropriate personal protective equipment is essential for minimizing risks associated with this project. Workers should consistently wear the following: hard hats to protect against falling objects; safety glasses or goggles to shield eyes from debris and flying particles; work gloves to protect hands from cuts and abrasions; hearing protection to mitigate the noise from power tools; and high-visibility clothing to enhance visibility, especially in poor lighting conditions. For fall protection, a full-body harness connected to a secure anchor point is mandatory when working at heights. Steel-toed boots provide foot protection from dropped materials and sharp objects.

Safe Work Practices at Heights

Working at heights presents significant fall hazards. To mitigate these risks, several precautions must be taken. A secure and properly anchored fall arrest system is mandatory. This system should be regularly inspected for damage or wear. Workers should maintain three points of contact with the roof at all times – two hands and one foot, or two feet and one hand – when moving around. Tools and materials should be hoisted up using appropriate lifting equipment instead of being manually carried up ladders. Ladders should be positioned on stable, level ground, and extended at least three feet above the roofline for secure access. Regular breaks should be taken to avoid fatigue, a major contributor to accidents at heights. Furthermore, all workers should receive adequate training in fall protection techniques before commencing work.

Emergency Procedures

A comprehensive emergency plan should be in place before starting the project. This plan should include procedures for dealing with various emergencies, such as falls, injuries from power tools, or medical emergencies. Designated emergency contact numbers, including local emergency services and a supervisor, should be readily available. A first-aid kit with appropriate supplies should be on-site and easily accessible. Workers should be trained in basic first aid and CPR. In the event of a fall, immediately call emergency services and follow established emergency response protocols. Secure the work area to prevent further accidents. Maintain detailed records of all incidents and injuries, including the circumstances leading to the event, actions taken, and any resulting injuries. A post-incident investigation should be conducted to identify contributing factors and implement corrective actions to prevent similar incidents in the future.

Visual Guide

A properly installed metal roof over asphalt shingles presents a visually appealing and durable roofing system. The success of the installation is evident in the seamless integration of the metal roofing with the underlying structure, showcasing precise panel alignment, meticulously crafted flashing, and clean trim work. The overall aesthetic depends heavily on the chosen metal roofing style and material.

Metal Roofing Styles and Materials

The visual impact of a metal roof significantly depends on the chosen style and material. Standing seam metal roofs, for example, feature distinct, vertical seams running the length of the panels, creating a clean, modern look. Ribbed metal roofing, on the other hand, displays parallel, raised ridges across the panels, offering a more textured appearance. The material itself also plays a crucial role. Galvanized steel often presents a silvery-grey finish, while aluminum can be found in a range of colors, including earth tones and darker shades. Copper roofs, known for their longevity and aesthetic appeal, develop a distinctive patina over time, shifting from a reddish-brown to a greenish-blue hue. Zinc roofs exhibit a similar evolution, gradually transforming from a silvery-grey to a bluish-grey.

Panel Alignment and Seam Work

Proper panel alignment is critical for a visually pleasing and leak-proof roof. Panels should be neatly aligned, with consistent spacing between them. Seams should be tight and even, indicating proper installation techniques. Visible gaps or misalignments suggest potential issues. In standing seam systems, the vertical seams should be perfectly straight and uniform across the entire roof surface. For ribbed metal roofing, the parallel ridges should maintain consistent spacing and run parallel to the roofline. Any visible buckling or waviness in the panels is indicative of improper installation or potential underlying structural problems.

Flashing Details

Flashing, the crucial component preventing water penetration around chimneys, vents, and valleys, should be virtually invisible from the ground. Properly installed flashing is seamlessly integrated with both the metal roofing and the underlying structure. The flashing material should match the metal roofing material in color and texture for a cohesive look. Visible flashing, especially with mismatched colors or materials, is a clear sign of poor workmanship and potential future leakage. Flashing around chimneys, for example, should extend several inches beyond the chimney’s base, and its edges should be carefully sealed to prevent water infiltration.

Trim Work and Accessories

The trim work, including ridge caps, gable vents, and eaves, significantly contributes to the overall aesthetic. These components should be neatly installed, matching the metal roofing material in color and texture. Consistent spacing and proper alignment are crucial for a professional appearance. For instance, ridge caps should sit snugly along the ridge line, with no gaps or visible fasteners. Gable vents should be evenly spaced and securely fastened, allowing for proper ventilation while maintaining a clean appearance. Eaves should be neatly finished with matching trim, protecting the roof edges and enhancing the overall aesthetic. Improperly installed or mismatched trim work can detract from the overall appearance of the roof.

Final Thoughts

Successfully installing a metal roof over existing asphalt shingles transforms your home’s exterior and enhances its longevity. By following the detailed steps outlined in this guide, you can confidently tackle this project, maximizing its benefits. Remember, proper preparation, careful execution, and adherence to safety protocols are key to a successful and durable installation. The result? A beautiful, protective roof that adds value and curb appeal to your property for years to come.