When considering a new roof installation, many homeowners think about the possibility of placing a metal roof over their existing shingles. While this may seem like a convenient and cost-effective solution, it comes with its own set of challenges and potential complications.
In this blog post, we will explore:
- Why you should think twice before installing a metal roof over shingles
- The benefits of metal roofs
- Cost considerations
Understanding Metal Roofs
First, let’s take a moment to appreciate why metal roofs are so popular. Metal roofing is known for its durability, energy efficiency, and aesthetic appeal. A well-installed metal roof can last up to 50 years or more, significantly outlasting traditional asphalt shingles. They reflect solar radiant heat, which can reduce cooling costs by up to 25% in the summer. Additionally, metal roofs are highly resistant to weather elements like wind, rain, and snow, making them an excellent choice for various climates.
The Temptation of Layering
The idea of layering a metal roof over shingles is tempting for several reasons:
- Cost Savings – By avoiding the tear-off process, homeowners can save on labor and disposal fees.
- Time Efficiency – The installation process can be quicker since there’s no need to remove the old shingles.
- Environmental Concerns – Avoiding the disposal of old shingles helps reduce waste.
However, despite these apparent benefits, the practice of installing a metal roof over shingles is fraught with potential issues.
1) Structural Concerns
Of course, structural issues are the biggest worry amongst homeowners. And rightly so!
Added Weight
One of the primary concerns with installing a metal roof over shingles is the added weight. While metal roofs are generally lighter than asphalt shingles, placing them on top of existing shingles adds additional stress to the roof structure. Over time, this added weight can impact the integrity of your roof’s structure, leading to sagging or even failure in extreme cases.
Roof Deck Condition
Installing a new layer of roofing material does not address underlying issues with the existing roof deck. If the decking is damaged, rotted, or weakened, simply covering it with a metal roof will not fix these problems. The underlying issues may worsen over time, potentially leading to leaks, structural damage, and costly repairs.
2) Moisture and Ventilation Issues
Layering roofing materials is also a recipe for water damage and related issues, including:
Trapped Moisture
Shingles are designed to shed water and allow your roof to breathe. When you install a metal roof over shingles, moisture can become trapped between the two layers. This trapped moisture can lead to mold growth, rot, and deterioration of both the shingles and the roof deck beneath.
Poor Ventilation
Proper ventilation is crucial for maintaining the longevity of your roof and the comfort of your home. Installing a metal roof over shingles can disrupt the natural airflow, leading to ventilation issues. Poor ventilation can cause heat buildup in the attic, leading to higher energy bills and a shortened lifespan for your roofing materials.
3) Aesthetic and Functional Concerns
If you’re going for the sleek look of a metal roof, you won’t find it by layering.
Uneven Surface
Shingles create an uneven surface, which can make it challenging to properly install a metal roof. The unevenness can lead to aesthetic issues, such as waves or ripples in the metal panels. Additionally, the metal roofing system relies on a smooth surface for optimal performance, and any irregularities can compromise its effectiveness.
Fastening Problems
Metal roofs require precise fastening to ensure they remain secure during high winds and other weather events. Installing a metal roof over shingles can make it difficult to achieve the proper fastening, as the existing shingles can interfere with the placement of screws and other fasteners. This can result in a less secure roof that is more prone to damage.
4) Voiding Warranties
Warranties are a great way to keep your roof and your bank account protected. But adding metal roofing on top of shingles can void your warranties on both products.
Manufacturer Warranties
Most metal roofing manufacturers have specific installation guidelines that must be followed to maintain the warranty. Installing a metal roof over existing shingles typically violates these guidelines, which can void the warranty. This leaves homeowners without protection should any issues arise with their new roof.
Insurance Concerns
Homeowners’ insurance policies may also be affected by the installation of a metal roof over shingles. Some insurance companies may refuse to cover damage resulting from improper installation or may increase premiums due to the higher risk of issues.
5) Energy Efficiency
Want to keep your energy costs low? Doubling up on roofing materials is not the way to do it!
Reflective Properties
One of the benefits of metal roofing is its ability to reflect solar radiant heat, reducing cooling costs in the summer. However, when installed over shingles, the reflective properties of the metal roof may be compromised. The trapped heat between the two layers can negate the energy-saving benefits, leading to higher energy bills.
Cost of Installing a Metal Roof
The cost of installing a metal roof can vary widely, depending on several factors such as the type of metal, the complexity of the roof design, and the region where you live. On average, homeowners can expect to pay between $8,000 to $19,000 for a metal roof installation.
Material Costs
- Steel and Aluminum: The most common metal roofing materials, steel and aluminum, are relatively affordable. Steel typically costs between $3 to $8 per square foot, whereas aluminum can range from $3.50 to $10.50 per square foot.
- Copper and Zinc: These premium options are more expensive, with copper costing between $14 to $25 per square foot and zinc ranging from $10 to $20 per square foot.
Labor Costs
Labor costs can be significant, accounting for about 60% of the total installation cost. Depending on the complexity and size of your roof, labor rates can range from $2.50 to $6 per square foot. Specialized techniques required for certain types of metal roofs can also contribute to higher labor costs.
Additional Costs
- Underlayment: A quality underlayment is essential for protecting your roof deck. This can add $0.25 to $0.75 per square foot to the overall cost.
- Flashing and Fasteners: These essential components for metal roofs generally cost between $1 to $3 per square foot.
- Roof Shape and Slope: Intricate roof designs and steep slopes require more labor and materials, increasing the total cost.
- Removal of Existing Roof: If you opt to remove your old shingles, expect to pay an additional $1,000 to $2,000 for the tear-off and disposal process.
Long-Term Savings
While the upfront cost of a metal roof can be higher than traditional roofing materials, it’s important to consider the long-term savings. Metal roofs have a longer lifespan, lower maintenance requirements, and can reduce energy costs. These factors together can offset the initial investment over time, making a metal roof a cost-effective choice in the long run.
Installing Your New Metal Roof The Right Way!
While the idea of installing a metal roof over shingles may seem appealing due to cost savings and convenience, the potential risks and drawbacks far outweigh the benefits. From structural concerns and moisture issues to aesthetic problems and the potential for voided warranties, the disadvantages are significant.
For those committed to getting a metal roof, the best course of action is to first remove the existing shingles. This approach ensures better performance, longevity, and peace of mind, knowing that your investment is secure and compliant with manufacturer guidelines.
If you’re considering a new roof installation and have questions about your options, feel free to book a consultation with our roofing experts at O’Donnell Roofing. We’ll help guide you through the process and ensure you make the best decision for your home’s needs.
