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How to Install Metal Roofing Over Shingles: A Step-by-Step Guide

Updated: Jun 22, 2023

Are you considering upgrading your home's roof to improve its durability, energy efficiency, and overall appearance? Metal roofing has gained popularity in recent years for its numerous benefits, including its long lifespan and low maintenance requirements. But what if you already have a shingle roof? Is it possible to install metal roofing over shingles? The answer is yes, and this blog post will guide you through the process of how to install metal roofing over shingles, helping you make informed decisions every step of the way.


In this comprehensive guide, we will cover the feasibility of learning how to install metal roofing over shingles, the necessary preparations, step-by-step installation instructions, and maintenance tips. We will also compare the costs and longevity of metal roofs and shingles to help you determine which option provides better value for your investment.


Short Summary

  • Assess local building codes, existing shingle condition and advantages/disadvantages of metal roofing to determine feasibility.

  • Prepare for installation by selecting appropriate material and ensuring proper ventilation.

  • Consider initial costs, longevity & durability when comparing metal roofs vs shingles for a cost effective investment.


Metal roof installation on a house

Assessing the Feasibility of Installing Metal Roofing Over Shingles


Before diving into the metal roofing installation process, it's crucial to assess the feasibility of installing metal roofing over shingles. This involves understanding local building codes, examining the condition of existing shingles, and considering the advantages and disadvantages of metal roofing. By conducting a thorough assessment, you can determine whether your existing shingle roof is suitable for a metal roof installation and avoid potential issues down the line.


Being well-informed about the factors affecting the feasibility of installing metal roofing over shingles will allow you to make the best decision for your home. Let's explore these factors in more detail, starting with local building codes.


Local Building Codes


It's essential to consider local building codes when planning to install metal roofing over shingles. Consult with your local building department to ensure you have permission for this type of installation.


Section 1511.3.1 of the 2018 International Building Code permits the installation of a new roof covering over an existing roof covering under specific conditions, such as using separate and complete roofing systems that do not rely on existing roofs and roof coverings for support.


By adhering to local building codes, you can avoid potential legal issues and fines.


Condition of Existing Shingles


Evaluating the condition of your existing shingles is a crucial step in determining whether they can support a metal roof. Before installing metal roofing over shingles, ensure that all leaks in the roof are fixed and any rotted wood sheeting or rafters are replaced. If the cost of repairing the current shingle roof is not feasible, it may be necessary to remove the existing shingles before installing the metal roof.


It's important to be aware of the potential risks associated with installing metal roofing over existing shingles. The additional weight of the metal roofing may cause buckling or sagging, resulting in structural damage. By carefully assessing the condition of your shingle roof, you can make an informed decision about whether it's suitable for a metal roof installation.


steel roof

Advantages and Disadvantages


Weighing the pros and cons of installing metal roofing over shingles is essential for making the right decision for your home. On the one hand, metal roofing is more resilient and aesthetically pleasing than shingles, resulting in lower labor costs and reduced landfill waste. Additionally, metal roofing provides an additional layer of insulation and can be manufactured from recycled materials, which can be recycled again at the end of its lifespan.


On the other hand, installing metal roofing over shingles may lead to significant issues that could result in additional time and expense for your roofing project. To prevent moisture from penetrating under your metal roof, it's essential to consult an expert and explore options such as ridge vents and furring strips. Ensuring proper ventilation is crucial to prevent mold, mildew, and rot caused by moisture trapped between roofing materials.


Additionally, it's important to review the roofing warranty language, as neglecting to adhere to installation instructions may invalidate the roofing material warranty or installation work warranty.


Metal roofing materials on a table

Preparing for Metal Roof Installation


Once you've assessed the feasibility of installing metal roofing over shingles, it's time to prepare for the installation process. This includes selecting the right metal roofing material, ensuring proper ventilation, and gathering the necessary tools and safety equipment.


Taking the time to properly prepare for your metal roof installation will help ensure a smooth and successful process.


Choosing the Right Metal Roofing Material


Selecting the appropriate metal material for your specific needs and preferences is an important step in the metal roof installation process. Some of the most popular options include steel, aluminum, zinc, copper, and stainless steel. Each material has its own advantages and disadvantages, depending on factors such as budget, durability, and aesthetic preferences.


For example, steel is known for its durability and cost-effectiveness, although it may be prone to rusting over time. Aluminum is lightweight and resistant to corrosion, yet is more costly than steel. Zinc, copper, and stainless steel are highly durable and resistant to corrosion, but also come with higher price tags.


By carefully considering your needs and preferences, you can choose the right metal roofing material for your home.


Ensuring Proper Ventilation


Addressing ventilation concerns is crucial to prevent moisture buildup and other issues when installing metal roofing over shingles. Proper ventilation for metal roof installation typically involves the use of ridge vents, and the International Residential Code recommends 1 square foot of ventilation per 150 square feet of attic floor area.


By ensuring proper ventilation, you can avoid potential problems such as mold, mildew, and rot caused by trapped moisture.


Gathering Tools and Safety Equipment


Acquiring essential tools and safety gear is key to a successful metal roof installation. Some of the necessary tools include a screw gun, cordless drills/drivers, shears, nibblers, and a seaming tool. In terms of safety equipment, a tie-off safety harness, non-skid footwear, and mesh netted “Fall-Saver” insulation laid underneath the roof are crucial.


Additionally, workers should wear proper slip-resistant soles and personal protective equipment, such as hard hats, safety glasses, ear plugs, ear muffs, respirators, gloves, steel-toed boots, long sleeves, long pants, and safety vests. Adequate preparation ensures a safe and efficient installation process.


Metal roof installation process

The Installation Process: Step-by-Step Instructions


Now that you're prepared for the metal roof installation, it's time to dive into the step-by-step instructions. In this section, we will cover the process of installing underlayment or purlins, attaching metal panels, and securing trim and flashing.


By following these detailed instructions, you can ensure your metal roofing is installed correctly and provides lasting protection for your home.


Installing Underlayment or Purlins


When installing metal roofing over shingles, you have two recommended methods to choose from: applying an approved underlayment over the existing shingles or installing 1x4 purlins over the shingles. Both options provide proper support for the metal roofing and help prevent damage caused by the shingles expanding and contracting.


To decide between using an approved underlayment or 1x4 purlins, consider the condition of your existing shingles and your local building codes. If the shingles are in excellent condition and you have obtained permission from your local building department, using an approved underlayment can be a viable option. Otherwise, installing 1x4 purlins may be the better choice.


Attaching Metal Panels


Correctly attaching metal panels to the roof structure is an essential part of the installation process. To do this, you should space screws between 24 and 30 inches, skipping every other rib.


This ensures proper alignment and spacing of the metal panels, providing a secure and stable metal roofing system.


Securing Trim and Flashing


Installing trim and flashing is a crucial step in protecting your metal roof against weather elements and enhancing its appearance. To secure trim and flashing, use nails or screws that are suitable for the material. Properly installed trim and flashing not only provide protection but also add a polished and professional look to your metal roof.


Metal roof inspection

Maintaining Your Metal Roof


A well-maintained metal roof can provide years of protection and enhance your home's curb appeal. In this section, we will share some tips and recommendations for keeping your metal roof in optimal condition.


Regular inspections are important to ensure that your roof is in good condition and that any potential problems are identified and addressed quickly. Cleaning and maintenance practices should also be carried out regularly to ensure that your roof remains in good condition and is able to function properly.


An image showing a professional conducting a regular inspection of a metal roof installed over shingles using the how to install metal roofing over shingles technique.

Regular Inspections


Conducting periodic inspections is crucial to maintaining your metal roof's longevity and performance. It's recommended to perform regular maintenance at least once a year, either by a roof maintenance service or the home/building owner, to identify any surface-level issues, check penetrations, and inspect screws.


During these inspections, look for surface-level issues such as dents, cracks, or rust. Additionally, check penetrations and screws to ensure they are secure. If you detect any issues during your inspection, address them promptly to avoid potential damage and costly repairs.


Depending on the nature of the issue, you may need to contact a roof maintenance service or repair it yourself.


Cleaning and Maintenance


To prolong your metal roof's lifespan and maintain its appearance, regular cleaning and maintenance are essential. It's suggested to clean your metal roof at least twice annually, or more frequently if needed. When cleaning your metal roof, use a non-abrasive detergent or dish soap, a bucket of water, and a microfiber cloth to wipe down the surface.


In addition to cleaning the roof itself, it's also important to clean gutters and drains twice a year. Regular cleaning and maintenance not only preserve your metal roof's appearance, but also ensure its continued performance and protection.


Comparing Costs: Metal Roofs vs. Shingles


When considering a metal roof, it's important to analyze the initial and long-term costs of metal roofs and shingles to determine which option provides better value for your investment.


In this section, we will compare the costs, longevity, and durability of metal roofs and shingles, helping you make an informed decision about your roofing project.


Metal roof cost comparison

Initial Costs


Metal roofing typically requires a large upfront cost. This is usually more than the cost of asphalt shingles. On average, the cost of metal roofs ranges from $6.50 to $12.00 per square foot installed, while the average cost of asphalt shingles is $3 to $5 per square foot installed.


Factors that can influence the cost of metal roofs include the type of metal roofing material used, the complexity of the roof, the size of the roof, and labor costs. By comparing prices and assessing your budget, you can determine which roofing option is the most cost-effective for your needs.


Longevity and Durability


The lifespan and durability of metal roofs are typically greater than that of shingles. Metal roofs can last up to 40-70 years, depending on the material, and are Class A fire-rated and non-combustible, making them highly resistant to catching fire.


In comparison, shingles have a shorter lifespan and may require more frequent maintenance and repairs. When evaluating the long-term value of metal roofing, it's important to consider not only the initial costs, but also the durability and longevity of the materials.


Over time, a metal roof may prove to be a more cost-effective investment due to its extended lifespan and lower maintenance requirements. By carefully weighing the costs, benefits, and potential drawbacks of metal roofs and shingles, you can make an informed decision that best suits your needs and preferences.


Summary


In conclusion, installing metal roofing over shingles can be a viable option for homeowners looking to upgrade their roof's durability, energy efficiency, and overall appearance. By assessing the feasibility, preparing for installation, following step-by-step instructions, and maintaining the metal roof, you can ensure a successful and long-lasting roofing project. While the initial cost of a metal roof may be higher than that of shingles, its extended lifespan and lower maintenance requirements often make it a more cost-effective investment in the long run. Take the time to consider your specific needs, preferences, and budget to determine whether a metal roof is the right choice for your home.


Frequently Asked Questions


Can you put metal roofing directly over shingles?


It is generally accepted that metal roofing can be installed over shingles, provided there aren't more than two existing layers of shingles. To ensure that your installation meets local building codes, check with your municipality before you begin the project.


Conclusion: It is possible to put a metal roof directly over shingles, as long as the existing shingle roof does not have more than two layers and is in accordance with local building code regulations.


Do you have to remove shingles before installing a metal roof?


It is generally recommended to remove shingles before installing a metal roof, as this is the best way to ensure a durable, long-lasting installation. This allows for thorough inspection of the underlying structure and helps minimize the risk of trapped moisture between the two layers.


Therefore, if possible, it is wise to tear off the old shingles before laying down the new metal roof.


Can you put metal roof over shingles without furring strips?


It is not recommended to put metal roofing over shingles without furring strips. The thermal expansion and contraction of the metal could rub against the shingle granules, leading to corrosion from the underside. Furring strips are necessary to provide air venting, and will also reduce moisture buildup.


Rigid insulation must also be installed between the wood strips to prevent condensation.

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