In the humid and unpredictable climate of Florida, a metal roof will last longer than a shingle roof. Installing a metal roof over existing shingles, known as a "metal-over-shingle" installation, is a common practice and is generally allowed by building codes. However, there are some important considerations and best practices to keep in mind.
First of all, a metal roof is an investment due to higher costs. The cost of metal roofing comes from the materials but also from the skills needed to install it. Therefore, you might think it's better to install a metal roof right over the existing shingles. Do the old roof shingles need to be removed and is this recommended? In theory, you do not have to tear off your shingle roof. Metal roofing can be installed over top of shingles. But, depending on the current condition of your roof, a professional roofer might disagree.
Metal roofing is very lightweight so it can be installed over shingles that are in good condition. But, before you have a local roofing company put a metal roof over your shingled roof, you will need to have an inspection and make sure your city's building department approves the installation.
Your roofer must inspect the plywood of your existing shingle roof to ensure no soft spots exist. Soft spots usually mean roof leaks. You will not be able to proceed if the wooden deck is leaking or sagging. A metal roof is screwed down and it needs to hold onto your roof's plywood. If it can't be screwed down this is a recipe for disaster in high winds and hurricanes.
In Florida, some municipal building codes state that you cannot have more than two layers of roofing materials on a single residential house. This is because most Florida homes cannot hold too much weight: the trusses may fall. Therefore, some counties will require you to remove any existing roofing materials rather than risk a roof cave-in. So the permitting process is very important for your safety.
If you do pass inspection and get a permit, a new underlayment may need to cover the existing shingle roof. This may also be required by your insurance company as an extra water barrier. It is also a good idea because metal roof panels can be affected by the old shingle granules below.
The second method involves installing a metal roof over a shingle roof with purlins. A purlin is a lightweight, horizontal beam or bar that is used for structural support in roofing. The purlins are screwed down to the roof deck, and the metal is installed on the purlins. This provides a flat surface for the metal roofing panels. Not all roofers may use this method.
Don't forget this important factor: if your property is part of a homeowners' association (HOA), check whether they have specific guidelines or restrictions on roofing materials and installations. They probably do!
Ultimately, installing metal roofing panels over existing shingles may NOT save you a lot of money. If the tear-off is your only cost concern, it might be worth doing it to ensure your new metal roof has a good foundation. Then you can enjoy decades in your Florida home with an energy-efficient, beautiful roof! Read more about metal roofing in our blog here.
Give Joe at Triangle Roofing a call to find out your best roofing options.