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

by Jul 17, 2023

Have you ever considered how to install a metal roof over shingles? It’s a modern approach that offers numerous advantages, like increased durability, longer lifespan, and a fresh aesthetic.

Ready to upgrade to a metal roof?

Let’s dive into the details!

Short Summary

  • Assess roof condition and consult local building codes prior to metal installation.
  • Professional preparation of the existing roof is essential, including cleaning, repair, underlayment & battens.
  • Consider pros/cons of DIY or hiring a professional for accuracy and warranty coverage.

Assessing Your Roof for Metal Installation

 

Before you get excited about the prospect of a new metal roof, there are some preparatory steps to consider. First, it’s vital to assess the condition of your existing roof. If your shingles are in good shape, that’s great news! Your roof may be a good candidate for a metal over shingle installation. However, if your roof has extensive damage, you may need to invest in repairs before proceeding.

Another key consideration is your local building code. While many jurisdictions allow metal roofs to be installed over one or two layers of shingles, they often disallow more than that. So, don’t forget to consult your local building department before starting your project.

Roof Condition and Damage

When evaluating your roof’s condition, start by inspecting individual existing asphalt shingles. Look for signs of damage, such as curling, cracking, or missing shingles. If the damage is widespread, you may need to repair or even replace your shingles before installing your new metal roof.

Another key factor to consider is the presence of a vapor barrier. This barrier prevents condensation from forming underneath the metal roofing materials, which is particularly important if you’re installing a metal roof over existing shingles.

Local Building Code Requirements

Your local building codes dictate the permissible number of shingle layers beneath a metal roof. In most cases, one or two layers are allowed, but installing a metal roof over shingles, especially three layers of shingles, is generally discouraged.

The type of underlayment required may also vary per your local building codes. This could be felt, a synthetic material, or even existing roof shingles in good condition. An underlayment is a must for metal roofing on an indoor residential space. It provides insulation and protection from weather elements such as rain and snow.

Choosing the Right Metal Roofing Material

 

Once you’ve assessed your steel roof and confirmed with your local building department, it’s time to choose the right metal roofing material for your home. The three most common types for residential use are standing seam metal roofing, metal shingles, and corrugated metal roofing.

Each of these materials, including asphalt shingles, has its pros and cons, and the best choice depends on your specific needs and circumstances. For example, stone-coated steel shingles are known for their hail resistance and can withstand wind speeds of up to 120 mph. However, they are heavier and more expensive than other options, with a material cost of between $200 and $350 per 100 square feet.

Preparing Your Roof for Metal Installation

 

Before you can install the metal panels, your existing roof needs to be prepared. This involves cleaning, repairing, and installing underlayment or battens. The cleaning process typically involves removing any accumulated debris like leaves and twigs and thoroughly cleaning gutters and drains. This is crucial to ensure that your new metal roof can drain properly and prevent water damage.

Cleaning and Repairing

In addition to cleaning, the roof surface should be inspected for leaks and structural damage. Any signs of water damage, such as discoloration or staining, as well as structural damage like sagging or cracking, should be repaired before proceeding.

If your existing roof has any rust, it should be removed with a wire brush or other rust-removing tool. Once the rust is removed, the surface of the metal panel should be cleaned with a mild detergent and water.

Underlayment and Battens

Once the roof is clean and any necessary repairs have been made, it’s time to install the underlayment or battens. These create a barrier between your existing shingles and the new metal roofing, helping to prevent moisture accumulation and ensure a smooth installation process.

Underlayment installation is particularly crucial if your roof has moderate damage. This additional layer can provide the following benefits for your new metal roof:

  • Protect your home from water intrusion
  • Enhance insulation
  • Improve sound dampening
  • Improve airflow qualities

Installing the Metal Roof Panels

 

With your roof prepared, the real fun begins – installing the metal roof panels! This process involves aligning the panels precisely and securing them firmly with exposed or concealed fasteners. It’s a meticulous task, but taking your time to do it right can result in a stunning and durable new roof that lasts for years.

Remember, metal panels should be installed one at a time, from the bottom up and starting at the edge farthest from the prevailing wind direction. This ensures a secure fit and helps prevent wind uplift.

Panel Alignment

Proper panel alignment is crucial to a successful metal roof installation. This starts with marking screw points on the panels to ensure that they are correctly positioned. Once your first piece is aligned properly, you can proceed with the rest of the panels, making sure to maintain a straight line. Remember, even a slight misalignment can throw off the entire installation, so take your time and double-check your work as you go along. Ensuring that each panel is properly aligned is essential for a successful installation. Take your time.

Fastening and Securing

Once your panels are properly aligned, it’s time to fasten and secure them. This involves using self-tapping screws with thin washers, which should be properly compressed to ensure a secure seal. The screws should be drilled into the flat part of the panel and placed every two feet along the panel.

Special clips should also be used to attach the panels to the roof deck. This will reduce the chances of fastener corrosion and roof leaks.

Sealing and Waterproofing

With your panels fastened securely, the next step is sealing and waterproofing your standing seam roof. This is an essential step that prevents leaks and ensures the durability of your metal roof.

To seal the panels, a sealant, such as caulk, is applied in the designated areas. This sealant prevents water from infiltrating between the two sheets of metal, ensuring a watertight seal.

Finishing Touches: Flashing, Trim, and Ventilation

 

You’re almost there! Once your panels are installed and sealed, it’s time to add the finishing touches to your metal roof. This includes installing flashing, trim, and ventilation, which not only enhances the aesthetic appeal of your roof but also offers protection against rain, snow, and wind.

Each of these components plays an essential role in the functionality and appearance of your metal roof. For instance, flashing and closure strips are used to ensure a watertight seal, while trim enhances the overall aesthetic of the roof.

Flashing Installation

Proper flashing installation is critical to prevent water infiltration and ensure a watertight seal. This involves cutting the flashing to fit the sidewall trim and then finishing it with a sealant.

After installing the flashing, outside closures are installed to seal between the flashing and the panel. This extra layer of protection ensures a secure seal and helps prevent water from seeping in.

Trim and Edge Finishing

Adding trim and edge finishing gives your roof a polished and professional appearance. The trim is attached to the roof with screws, and the ends are spliced together by overlapping them and securing them with screws.

Remember, the eave and gable trim should be installed before the ridge cap for optimal results. The ridge cap should be overlapped at the ends and secured with screws for installation.

Ventilation Considerations

Lastly, let’s discuss ventilation. Proper ventilation is crucial to maintain airflow and prevent condensation in your attic space. This can prevent moisture buildup and heat retention, which can extend the lifespan of your roof.

Ridge vents are the optimal choice for metal roofing, with the ventilation system balanced with 50% located at the eaves and 50% at the upper portion of the roof. Following the International Residential Code’s recommendation of a ventilation ratio of 1 square foot per 150 square feet of attic floor space can ensure that your roof is adequately ventilated.

Pros and Cons of Installing Metal Roofing Over Shingles

 

Now that you’re familiar with the process of installing a metal roof, let’s weigh the pros and cons. On the positive side, a metal roof offers an attractive look, doesn’t require additional coatings, and can last up to 50 years or more.

However, there are some drawbacks to consider. If your shingle roof is worn or leaking, you’ll need to remove the shingles before installing the metal roof. There are also questions about the installation process, and you’ll need to find a reliable and experienced roofing contractor.

Hiring a Professional vs. DIY Metal Roof Installation

 

The decision between hiring a professional or attempting a DIY metal roofing installation is a personal one. While many homeowners are attracted to the cost savings of a DIY project, keep in mind that a professional will ensure correct metal roof installation and provide a warranty for both workmanship and material defects.

On the flip side, attempting a DIY metal roof installation can be a rewarding project for the handy homeowner. However, it’s important to consider safety precautions and the potential for mistakes, especially if you’re new to roofing.

Summary

In conclusion, installing a metal roof over shingles is a viable option for homeowners looking to upgrade their roofing solution. While there are certain considerations to keep in mind, such as the condition of your existing roof and your local building codes, the benefits of a durable, long-lasting, and aesthetically pleasing metal roof often outweigh the challenges. Whether you choose to hire a professional or tackle the project yourself, we hope this guide helps you on your journey to a successful metal roof installation.

Frequently Asked Questions

Can I install metal roofing directly over shingles?

It is generally safe to install metal roofing directly over shingles, as the weight of the material won’t damage existing roofing and the extra layer of protection can help insulate a home.

Metal roofing is light weight, so it is the perfect material to be installed over an existing shingle roof.

What are the benefits of installing a metal roof over shingles?

Installing a metal roof has many benefits over traditional shingles; it provides an attractive look, doesn’t require extra coatings, and offers a long-term lifespan of up to 50 years.

Metal roofs are also more durable than shingles, and can withstand extreme weather conditions such as hail, high winds, and heavy snowfall. They are also fire-resistant and can help reduce energy costs. Additionally, metal roofs are easy to install and require minimal maintenance.

How do I prepare my roof for metal installation?

Clean and repair your roof, then install underlayment or battens to ensure a secure base for metal installation.

What is the process for installing the metal roof panels?

Installing metal roof panels requires precise alignment and secure fastening using either exposed or concealed fasteners.

Fasteners can be either exposed or concealed, depending on the desired aesthetic. The installation process requires careful alignment and secure fastening to ensure the roof panels are properly installed.

Should I hire a professional or attempt a DIY metal roof installation?

Given the potential risks and mistakes that could be made, hiring a professional metal roofer is recommended for ensuring correct installation and providing a warranty.

This will help to ensure that the roof is installed correctly and that any issues that arise are covered by the warranty.

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