When making the transition from asphalt shingles to metal roofing, you will need to decide what to do with your old shingle roof. One option is to have the old shingles removed before installing the new metal roof, but you can also choose to have the metal roof installed over the existing shingle roof. This may be surprising to some, but it is a viable option for metal roofing installation.
When it comes to upgrading from asphalt shingles to a metal roof, the decision should be carefully considered based on individual circumstances. At NC Metal Roofing Experts, we have over 20 years of experience helping customers navigate this decision, as every roof is unique and requires a case-by-case assessment.
This article will provide you with information on re-roofing, which involves installing a new roof over an existing one. Additionally, we will discuss four factors to consider when deciding whether to remove your asphalt shingle roof before installing a metal roof.
Installing Metal Roof Over Shingles Pros And Cons
Overlaying or re-roofing, the process of putting a new roof over the old one, offers numerous benefits.
Pros Of Putting A Metal Roof Over Shingles
By not removing the asphalt roof first, you can save on labor costs, as it results in less work for the contractor. Additionally, this method provides added insulation protection for your home by having extra roofing layers, allows for faster installation as less labor is required, and is eco-friendly because the old asphalt shingles will not have to be thrown away.
Metal is an ideal material for re-roofing due to its lightweight nature, weighing less than one pound per square foot. This means that a new metal roof will not add significant stress to your home, even if your old asphalt shingle roof is still in place underneath.
Cons Of Putting A Metal Roof Over Shingles
Certain building codes restrict it. Issues with shingles can impact the new roofing. Trapped moisture can be a problem. This could void your warranty.
We provide in-depth information on each of these issues and the important questions to consider before making the decision to install a metal roof over your shingle roof.
1. Does The Building Code Allow For A Metal Roof To Be Placed Over Shingles?
If the local building code specifies that existing shingles must be removed, then the decision is straightforward.
It is important to note that while some building codes may permit two layers of roofing on a structure, this is not always the case. It is crucial to review your local building codes to determine what is allowed in your specific area. Failure to comply with building codes can lead to costly fines.
2. Are There Problems With Your Previous Roof?
Putting a new roof on will not solve any existing problems with your old roof. In fact, it may exacerbate them over time.
Before installing a metal roof over an existing shingle roof, it’s important to ensure that the structure of your home can handle the additional weight. Signs of potential problems from the weight of your roof include buckling trusses or sagging roof decking. Prior to installation, be sure to address any rotten wood sheeting or rafters to prevent further issues.
If you have leaks in your asphalt shingle roof, it’s important to address these problems. Water damage to parts of the roofing system will need to be repaired or replaced. You may have already noticed water damage issues that led you to consider getting a new roof. Ignoring these issues could result in a shorter lifespan for your new roof and more expenses in the future.
3. Can Moisture Get Trapped Between The Metal And Asphalt Shingles?
A metal roof is resistant to rotting and mildew, but it’s important to ensure that moisture doesn’t seep in between the new metal roofing panels and the old asphalt shingle roof to fully enjoy these benefits.
The presence of moisture between these surfaces can lead to mold and rot, ultimately causing expensive repairs.
Here are two ways to eliminate trapped water vapor:
Furring strips are specifically designed to elevate the metal roofing and create ventilation gaps between the metal and shingles, allowing for proper airflow.
It is important to note that each roof is unique and should be assessed by the roofing contractor in order to determine the best course of action for your specific roof. With that being said, it is recommended that all metal roofs be equipped with roofing underlayment, regardless of whether it is a new installation or being installed on top of an existing shingle roof. This underlayment provides an additional layer of protection against moisture.
Will the warranty for the metal roof be void if it is installed over shingles?
The terms of your metal roof warranty may differ depending on the manufacturer. It is important for you or your installer to carefully review the metal roof warranty to ensure that you are not violating the terms by installing it over asphalt shingles. Failing to do so could result in your brand new roof being left without any coverage.
Is It OK To Put A Metal Roof Over Shingles?
In certain circumstances, it can be acceptable to install a metal roof over existing shingles. It is crucial to carefully evaluate the unique factors of your roof replacement project before making a decision about whether to remove the old roof or not.
You should remove your old asphalt shingle roof before installing a metal roof when:
There are indications of structural problems due to the weight of your roof. The installation over asphalt shingles will void your metal roof warranty, and you must comply with local building codes.
You may decide to install a metal roofing material over old asphalt shingle roof when:
The roofing underlayment and vented ridge cap you are using will help prevent moisture buildup, which is in compliance with your local building code. Additionally, by saving on labor costs, you may be able to save money in the short term. Despite this, you will still be eligible for warranty coverage.
Proper installation is essential for the durability of your metal roof, regardless of the method you choose. The process of installing a metal roof differs from that of a shingle roof, requiring unique skills. It is highly recommended to enlist the services of a qualified metal roofing contractor for the installation of your new roof.