Metal roofing over asphalt shingles presents a compelling alternative to complete roof replacement, offering potential cost savings and extended lifespan. This approach, however, necessitates careful consideration of various factors, including structural integrity, material compatibility, and adherence to local building codes. Understanding these aspects is crucial for a successful and safe installation.
This exploration delves into the intricacies of installing metal roofing directly over existing asphalt shingles, examining the financial implications, structural requirements, installation procedures, material choices, and regulatory considerations. We aim to provide a comprehensive guide for homeowners considering this cost-effective roofing solution.
Cost Comparison
Choosing between installing a metal roof over existing asphalt shingles or opting for a complete tear-off before installation involves a significant financial decision. Understanding the upfront and long-term costs associated with each approach is crucial for making an informed choice. This section will analyze the cost differences and long-term savings potential of each method.
Upfront Cost Comparison
The initial investment for a metal roof installation varies considerably depending on the chosen method. A complete tear-off adds significant labor and disposal costs, while installing over existing shingles is generally cheaper upfront. The following table illustrates a typical cost comparison, acknowledging that actual costs can fluctuate based on location, roof size, and material choices. These figures are estimates and should be verified with local contractors.
| Item | Tear-off & Metal | Over Asphalt Shingles | Cost Difference |
|---|---|---|---|
| Material Costs (Metal Roofing) | $10,000 – $20,000 | $10,000 – $20,000 | $0 |
| Labor Costs (Installation) | $5,000 – $10,000 | $3,000 – $6,000 | $2,000 – $4,000 (Tear-off is more expensive) |
| Tear-off & Disposal | $2,000 – $5,000 | $0 | $2,000 – $5,000 (Tear-off adds significant cost) |
| Permits & Inspections | $500 – $1,000 | $500 – $1,000 | $0 |
| Total Estimated Cost | $17,500 – $36,000 | $13,500 – $27,000 | $4,000 – $9,000 (Tear-off is more expensive) |
Long-Term Cost Savings
While the upfront cost of installing a metal roof over existing shingles is lower, the long-term benefits of metal roofing significantly outweigh those of asphalt shingles.
The following factors contribute to substantial long-term cost savings:
- Extended Lifespan: Metal roofs boast a significantly longer lifespan (50-75 years) compared to asphalt shingles (15-20 years), reducing the frequency of costly replacements.
- Reduced Maintenance: Metal roofs require minimal maintenance, unlike asphalt shingles which are prone to damage from weather, requiring repairs and potential premature replacement.
- Improved Energy Efficiency: Metal roofing’s reflective properties reduce heat absorption, leading to lower energy bills for cooling, especially in warmer climates. A study by the Oak Ridge National Laboratory showed a significant reduction in cooling loads for homes with reflective roofing.
- Increased Home Value: The durability and longevity of a metal roof often increase a home’s resale value, providing a return on investment.
Potential Hidden Costs of Installing Over Asphalt Shingles
Installing a metal roof over existing asphalt shingles may seem cost-effective initially, but potential hidden costs can negate the savings.
These include:
- Increased weight on the roof structure: Adding the weight of a metal roof to an existing structure might necessitate costly reinforcements or repairs to ensure structural integrity. For example, an older home with a weakened roof frame could require significant structural work before the new roof can be installed safely.
- Potential for moisture buildup: If not properly installed, a metal roof installed over asphalt shingles can trap moisture, leading to mold, rot, and other costly repairs. This is especially true if the existing underlayment is damaged or inadequate.
- Uneven surface: Variations in the existing asphalt shingle surface might result in an uneven final metal roof appearance and potentially compromise the watertight seal.
- Warranty issues: Some metal roofing manufacturers may void warranties if the roof is installed over existing shingles due to potential issues arising from the underlying layer.
Structural Considerations
Installing metal roofing over existing asphalt shingles presents several structural considerations. The added weight of the metal roofing, along with the existing asphalt shingles, can significantly increase the load on the roof structure, potentially exceeding its design capacity. Ignoring these considerations can lead to structural damage, leaks, and even roof collapse. Careful assessment is crucial before proceeding with such an overlay.
The structural integrity of a roof when installing metal roofing over existing asphalt shingles depends on several factors, including the age and condition of the existing roof structure, the type and weight of the metal roofing system being installed, and the overall climate conditions. The added weight of the metal roofing system, typically ranging from 50 to 150 pounds per square (100 square feet), adds considerable load to the existing rafters, trusses, and supporting walls. This additional weight, combined with the weight of the existing asphalt shingles, snow, and other potential loads, can easily exceed the structural capacity of older or poorly constructed roofs.
Roof Structure Weight Limitations and Stress Assessment
Determining the existing roof’s load-bearing capacity is paramount. This involves evaluating the current structural members (rafters, trusses, and supporting walls) for signs of deterioration, such as rot, insect infestation, or excessive deflection. A qualified structural engineer can perform a thorough inspection and provide a detailed report outlining the roof’s capacity and any necessary reinforcements. This report should clearly state whether the roof can safely support the added weight of the metal roofing system and the existing asphalt shingles. Without such an assessment, proceeding with the overlay carries significant risk. For example, a roof designed for a 30 psf (pounds per square foot) snow load might only have 5 psf of capacity left for additional roofing materials, making an overlay impractical. The weight of the metal roofing system and the asphalt shingles could easily exceed this remaining capacity.
Necessary Structural Evaluations and Reinforcements
A step-by-step procedure for assessing roof structure suitability for metal roofing overlay includes:
- Visual Inspection: A thorough visual inspection of the roof structure, including rafters, trusses, and supporting walls, should be conducted to identify any signs of damage, decay, or deterioration.
- Load Calculation: Calculate the total weight of the existing asphalt shingles and the proposed metal roofing system. This should include the weight of the metal panels, fasteners, underlayment, and any additional components.
- Structural Capacity Determination: Determine the existing roof’s load-bearing capacity using engineering calculations or by consulting a structural engineer. This step might involve reviewing original building plans or performing load tests.
- Comparison and Analysis: Compare the calculated weight of the new roofing system with the determined load-bearing capacity of the existing roof structure. If the weight exceeds the capacity, structural reinforcements are necessary.
- Reinforcement Design and Implementation: If reinforcements are needed, a structural engineer should design and oversee the implementation of these reinforcements. This might involve adding additional support beams, strengthening existing rafters or trusses, or other appropriate measures.
Homeowner’s Checklist for Roof Suitability
Before considering a metal roof overlay, homeowners should use this checklist to assess their roof’s suitability:
- Age of the roof: Older roofs are more likely to have structural weaknesses.
- Roof condition: Are there any signs of rot, insect damage, or significant deflection in the rafters or trusses?
- Attic access: Inspect the attic for any signs of sagging, water damage, or other issues.
- Recent repairs: Have there been any recent major repairs or renovations to the roof structure?
- Local building codes: Check local building codes for any restrictions or requirements regarding metal roofing overlays.
- Professional inspection: Consult with a qualified structural engineer or roofing contractor to conduct a thorough assessment of the roof’s structural integrity.
Installation Process
Installing a metal roof over existing asphalt shingles requires careful planning and execution to ensure a long-lasting and leak-proof result. This process involves several key steps, best practices for ventilation, and the critical use of underlayment and flashing. Proper installation minimizes the risk of future problems and maximizes the lifespan of the new roofing system.
The following steps outline a typical metal roofing installation over asphalt shingles:
- Preparation: Begin by thoroughly inspecting the existing asphalt shingle roof for any damaged areas. Repair or replace any compromised shingles, ensuring a solid base for the new metal roof. Remove any loose debris or obstructions. Also, ensure proper disposal of the old shingles according to local regulations.
- Underlayment Installation: Install a high-quality underlayment over the existing shingles. This provides an extra layer of protection against moisture penetration and acts as a secondary water barrier. Overlap the underlayment sheets according to manufacturer’s instructions, creating a seamless waterproof membrane.
- Flashing Installation: Install flashing around chimneys, vents, skylights, and valleys. Proper flashing is crucial to prevent water from seeping into these vulnerable areas. Flashing should extend several inches above and below the intersecting surfaces and be sealed tightly to prevent leaks.
- Metal Panel Installation: Begin installing the metal roofing panels, starting at the lowest point of the roof and working your way up. Overlap the panels according to the manufacturer’s specifications, ensuring proper sealing and water tightness. Secure the panels with appropriate fasteners.
- Ridge Cap Installation: Once the main panels are installed, install the ridge cap to cover the peak of the roof. This protects the seam from water damage and enhances the roof’s aesthetic appeal.
- Final Inspection: Conduct a thorough inspection of the entire roof to ensure all panels are securely fastened and properly sealed. Check for any gaps or leaks and address any issues immediately.
Ventilation Best Practices
Adequate ventilation is essential to prevent moisture buildup under a metal roof, which can lead to condensation, rust, and structural damage. Proper ventilation involves creating a continuous airflow from the soffit vents at the eaves to the ridge vents at the peak of the roof. This airflow helps to remove trapped moisture and maintain a stable temperature within the attic space. Installing ridge vents and ensuring adequate soffit ventilation is crucial for preventing moisture-related problems. The ventilation system should be designed to allow for at least 1/150th of the attic floor area for ventilation. For example, a 1500 square foot attic should have at least 10 square feet of ventilation.
Underlayment and Flashing Importance
Underlayment serves as a secondary water barrier, protecting the roof structure from moisture damage in case the primary roofing system fails. Flashing, on the other hand, seals vulnerable areas where the roof intersects with other components, such as chimneys, walls, and vents. Proper installation of both is critical for preventing leaks and extending the lifespan of the roof.
Correctly Flashed Roof Section Description
Imagine a chimney penetrating the roof. Around the chimney, a layer of flashing extends upwards several inches above the roofline and downwards several inches below the roofline. This flashing wraps around the chimney, creating a continuous waterproof barrier. The lower section of flashing overlaps the underlayment and is sealed with roofing cement. The upper section overlaps the roofing panels and is secured with fasteners. This creates a watertight seal around the chimney, preventing water from penetrating the roof structure. Similar flashing details are used around other penetrations such as vents and skylights.
Material Compatibility
Installing metal roofing over existing asphalt shingles presents several compatibility considerations. The success of the project hinges on choosing the right metal roofing material, understanding its interaction with the underlying shingles, and employing appropriate fasteners and sealants. Ignoring these factors can lead to premature failure of the roofing system, leaks, and costly repairs.
Metal Roofing Material Compatibility with Asphalt Shingles
Different metal roofing materials exhibit varying degrees of compatibility with asphalt shingles. Steel, aluminum, and copper each possess unique properties influencing their suitability for this type of overlayment. Steel roofing, often galvanized or coated with zinc, is a popular and cost-effective choice, offering good strength and durability. However, steel’s susceptibility to rust necessitates careful consideration of moisture management. Aluminum roofing, known for its lightweight nature and corrosion resistance, is a more expensive option but provides excellent longevity. Copper roofing, while exceptionally durable and aesthetically pleasing, is significantly more costly than steel or aluminum and requires specialized installation techniques. The compatibility of each with asphalt shingles is primarily related to their ability to withstand potential moisture buildup and the structural integrity of the existing roof.
Challenges of Installing Metal Roofing Over Different Asphalt Shingle Types
The type of asphalt shingle significantly impacts the installation process of a metal roof overlay. Composition shingles, with their thicker profile and greater dimensional stability, generally present fewer challenges than thinner 3-tab shingles. Architectural shingles, characterized by their textured surface and heavier weight, require careful consideration of the increased load on the underlying structure. The main challenge across all shingle types is ensuring a smooth, even surface for the metal panels to rest on, preventing unevenness or potential points of stress that could lead to leaks. Older, degraded shingles may also pose a risk, necessitating a thorough inspection and potential repairs before metal installation. For example, if significant shingle damage is present, it might be necessary to remove the damaged shingles before installing the metal roof.
Fastener and Sealant Selection Guide for Metal Roofing Over Asphalt Shingles
Choosing the correct fasteners and sealants is critical for a successful metal roof overlay. The table below summarizes appropriate selections for different metal roofing materials. Incorrect selection can compromise the waterproof integrity of the roof and lead to costly repairs.
| Metal Roofing Material | Recommended Fasteners | Recommended Sealants |
|---|---|---|
| Steel | Stainless steel screws with EPDM washers | Butyl rubber or polyurethane sealant |
| Aluminum | Aluminum screws with EPDM washers | Silicone or polyurethane sealant (compatible with aluminum) |
| Copper | Copper or stainless steel screws with EPDM washers | Silicone or polyurethane sealant (compatible with copper) |
Permits and Regulations
Installing a metal roof over existing asphalt shingles requires navigating the often complex world of building permits and regulations. This process varies significantly depending on your location, and failure to obtain necessary permits or adhere to local codes can result in fines, delays, and even the need for costly remediation work. Understanding these requirements is crucial for a smooth and legal project.
The permitting process for metal roofing over asphalt shingles generally involves submitting an application to your local building department. This application typically requires detailed plans outlining the proposed work, including specifications of the materials to be used, and often necessitates a site inspection before, during, and after the installation. The specific requirements, however, can vary considerably.
Permit Requirements
The precise documents and information needed for a permit application will differ depending on your local jurisdiction. However, common requirements include a completed application form, detailed project plans (often including elevations and cross-sections showing the proposed roofing system), material specifications (including manufacturer’s data sheets for the metal roofing and underlayment), and proof of insurance for the contractor. Some jurisdictions may also require a structural engineer’s assessment, especially if the existing roof structure’s ability to support the added weight of the metal roofing is questionable. For instance, a city in a high-wind zone might require specific wind-load calculations to be included in the permit application. In contrast, a jurisdiction with stricter environmental regulations might require documentation demonstrating the proper disposal of removed asphalt shingles.
Importance of Adherence to Local Building Codes and Regulations
Adhering to local building codes and regulations is paramount for several reasons. Firstly, it ensures the safety and structural integrity of your home. Metal roofing, while durable, needs to be installed correctly to withstand environmental stresses like wind, snow, and rain. Building codes provide minimum standards for installation, ensuring the roof performs as intended. Secondly, compliance protects your investment. Non-compliant work might not be covered by insurance in the event of damage, leaving you with significant financial burdens. Finally, failing to comply with building regulations can result in hefty fines, stop-work orders, and even legal action. In some cases, you may be required to completely remove and reinstall the roofing system if it’s deemed non-compliant. For example, a homeowner who failed to obtain the necessary permits and installed a metal roof that violated local fire codes could face significant penalties.
Resources for Determining Local Building Codes and Permitting Requirements
Homeowners can access information on local building codes and permitting requirements through several avenues. The most direct approach is to contact your local building department directly. Their website often contains detailed information about permit applications, required documentation, and relevant codes. You can also search online for your municipality’s building codes, often available as downloadable PDF documents. Furthermore, consulting with a licensed contractor experienced in metal roofing installations is highly recommended. These professionals are familiar with the specific requirements in your area and can guide you through the permitting process. Finally, state and regional associations of building officials often provide resources and information that can be helpful in navigating the complexities of local regulations.
Warranty and Insurance
Installing metal roofing over existing asphalt shingles presents some interesting considerations regarding warranties and insurance. Understanding how this impacts both your existing coverage and your potential costs is crucial before proceeding. This section will clarify the potential effects on existing warranties and homeowner’s insurance premiums, as well as typical metal roofing manufacturer warranties.
Effects on Existing Warranties
Laying metal roofing over asphalt shingles may void existing warranties on the underlying asphalt shingles. Most asphalt shingle manufacturers’ warranties explicitly state that altering or covering the shingles will invalidate the warranty. This is because the added weight and potential for moisture entrapment can affect the longevity and performance of the original roofing material. Similarly, warranties on the underlying roof deck or structural components might also be affected if the installation process damages them. It’s crucial to check the specific terms and conditions of your existing warranties before undertaking this type of roofing project. Consulting with a roofing professional and your insurance provider can help clarify these potential issues.
Impact on Homeowners Insurance Premiums
The effect of installing a metal roof over asphalt shingles on homeowners insurance premiums is not always predictable. Some insurance companies may view this as an improvement, potentially leading to a slight reduction in premiums due to the increased durability and fire resistance of metal roofing. However, others may not recognize this as a significant enough improvement to warrant a change. In some cases, the added weight of the metal roofing might be a factor considered by the insurer, though this is less common. The best way to determine the impact is to contact your insurance provider and discuss the specific details of your project before starting the work. Providing them with information about the metal roofing manufacturer, the type of installation, and the overall project cost will allow for a more accurate assessment.
Metal Roofing Manufacturer Warranties
Metal roofing manufacturers typically offer comprehensive warranties covering material defects and workmanship. These warranties usually range from 30 to 50 years, and sometimes even longer, depending on the manufacturer and the specific product. The warranty often covers issues such as rust, corrosion, and fading. However, it’s important to understand that warranties often have limitations. For example, they might not cover damage caused by severe weather events, improper installation, or normal wear and tear. Review the warranty details carefully before making a purchasing decision, paying close attention to exclusions and limitations. Consider requesting a copy of the warranty from the manufacturer or supplier before the installation begins, ensuring you fully understand the terms and conditions. A reputable installer will also be knowledgeable about the warranty and can help you understand its implications.
Final Wrap-Up
Ultimately, the decision to install metal roofing over asphalt shingles involves a careful weighing of costs, structural assessments, and adherence to building codes. While potentially offering significant long-term savings and durability, a thorough understanding of the process and potential challenges is paramount. This guide serves as a starting point for informed decision-making, encouraging homeowners to consult with qualified professionals to ensure a safe and successful project.