Can a Metal Roof Be Installed Over Shingles?

Metal roofing has gained popularity for businesses and homeowners alike and many curious building owners wonder the same thing: “Can I put a metal roof over shingles?” It’s a good question and we will go over the reasons this short cut can lead to disaster. 

Why Installing a Metal Roof Over Shingles Isn’t Ideal

Issues with Adhesive Membranes on Shingles

The most common metal roof installation includes a self-adhesive membrane, which is specially designed to bond two flat, smooth surfaces. This membrane not only bonds the two layers but it also provides a barrier against water and other elements. Due to shingles having ridges and valleys, attempting to put a metal roof over shingles creates gaps in the adhesion between the metal roofing panels and the plywood roof deck. This is compounded by the natural expansion and contraction metal roofs experience with temperature changes. A correctly installed metal roof using a self-adhesive membrane on a flat surface is specially formulated to allow those fluctuations to happen without creating gaps that might let water in. That’s just one aspect of why putting a metal roof over shingles is never recommended.

Structural Concerns with Metal Over Shingles

Another consideration is how heavy a metal roof and existing shingle roofs are and the risk of structural damage that could be caused by putting a metal roof over shingles. In some areas, it’s legal to layer 2 or even 3 layers of shingled roofing on a house, drastically increasing the weight load it must bear. Metal roofs are heavier than they appear, and adding a metal roof on top of an existing shingles could strain the structural integrity of the home over time. Another consideration is ventilation. A properly vented roof helps your home be more energy efficient. If existing roof shingles are not removed prior to a metal roof installation, this can lead to issues with climate control in your building. 

Another safety consideration is fire. Metal roofs are not fireproof but they do offer some benefits, such as being non-combustible, so if you live in an area prone to wildfires, they will not be ignited by burning debris or embers, whereas asphalt shingles and wood shingles are likely to catch on fire. If you attempt to install a metal roof over existing shingles and your building does experience a fire, those shingles are combustible. A layer of burning shingles under your roof adds to the risks of injuries and trapped heat against the underside of your metal roof can damage the integrity of the roof too. 

Please note that while metal roof installations are fire-resistant, they are NOT FIREPROOF and combustible items under them can still ignite if they get hot enough.

Standing Seam Metal Roof Installation

At Preferred Roofing, we specialize in standing seam metal roof installation. This type of metal roofing installation is known for its durability, sleek aesthetic appearance and long-term efficiency. By providing a seamless barrier against the elements, there is a reduced risk of leaks, making them a low-maintenance and high-performing roofing system. 

Common Question: Can I Put a Metal Roof Over Shingles?

So, can you install a metal roof over existing shingles? The more important question isn’t can you; technically you can, but SHOULD you put a metal roof over shingles? The simple answer is no; you should not. The risks of leaving shingles under a metal roof are not worth the minor savings that this shortcut may have in the short term. A reputable roofing company will never recommend that you install a metal roof over existing shingles for many of the reasons we have already outlined. 

Why Removing Shingles Before Metal Roof Installation is Crucial

As we’ve covered, removing existing shingles before installing a metal roof ensures that your roof deck is in good condition before installing a metal roof, creating a firm, smooth foundation for the self-adhesive membrane to bond between your metal roof installation and the roof deck. It also reduces the weight on your building and ensures proper ventilation and safety.

If you’re ready to install a high-quality metal roof in and around the Kansas City area, contact Preferred Roofing & Seamless Guttering. We offer expert installation and a commitment to excellence. Contact us today for a free estimate and professional advice.