Prized for their affordability and impressive durability, metal roofs can offer big benefits in certain situations. But can they be applied directly over shingled roofs? Here’s what you should know.
Can it Be Done?
In almost every instance, you can lay down new metal roofing over the top of an existing shingle roof. Although it is very durable, metal roofing is light; while asphalt shingles can weigh up to four pounds per square foot, metal roofing can weigh just one pound per square foot. Adding metal roofing over shingles won’t significantly add to the overall load, so there’s generally no reason to remove the existing shingles in most cases.
Is it a Good Idea?
As with most things, this depends on the circumstances, including the type of structure and your overall goals. Because you don’t have to strip away the existing roofing material, metal roofs can provide cost savings. They can also provide additional insulation above a house to prevent cold and warm air from escaping. Metal roofs also reflect heat away from their surfaces instead of absorbing it. This prevents the extra insulation from your underlying shingle roof from acting as a heat trap.
With that said, there are a few considerations you need to make before deciding to install a metal roof. These include:
- If your existing shingle roof has any leaks, you will need to inspect for rotting sheeting or rafters and fix these potential issues before installing the new roof.
- You need to check with your local HOA, zoning and building departments to make sure they don’t forbid metal-over-shingle installations.
- If the existing roof’s weight has promoted any structural issues such as buckled trusses or sagging decking, this will need to be repaired first.
It’s also usually best to consider adding some kind of underlayment between the shingles and new roof to keep granules from contacting the metal and promoting corrosion.
Advantages of Metal Roofing
In addition to potential cost benefits, metal roofing offers other advantages, including:
- Long lifespans: A well-installed metal roof can last four to five decades without the need for replacement.
- Durability: Metal roofs can withstand very intense weather events, including everything from ice storms and searing summer heat to pounding hail and gale-force winds.
- Low maintenance: Properly installed metal roofs don’t usually require routine maintenance or expensive repair jobs.
- Reduced cooling bills: Because they have special coatings that allow them to reflect heat, metal roofs promote cooler interior temperatures so you don’t have to use your AC system as much.
Installing a Metal Roof Over Shingles
There are two primary methods for installing a new metal roof over existing shingles. The first involves running a new underlayment over the shingles. The underlayment can act as an effective line of defense in case water somehow migrates beneath the metal roof. The underlayment can also act as a buffer between the shingle roof and the metal roof, preventing the granules from degrading the metal over time.
The second method involves using battens or purlins to install the new metal roof. With this method, the contractor screws down purlins into the roof deck, depending on the design of the roofing panels. The metal roof is then installed onto the purlin framing. This method provides the contractor with a flat surface for the metal roofing panels without having to combat the many grooves and other irregularities associated with shingles surfaces.
A reputable roofing contractor can help you determine the most effective installation method for your home. They can also advise you on whether a metal roof is a good idea for your particular situation.
Need a cost-effective way to replace or repair your existing roof? A to Z Roofing is Colorado’s top choice for affordable and reliable roofing services. For nearly three decades, we’ve been restoring, repairing and replacing roofs using top-quality products installed by seasoned technicians who always put our customers first.
If your home’s roof is past its prime or has been damaged by harsh weather, our skilled experts can help. We know how difficult it can be to find a trustworthy local roofing contractor. A locally owned business, A to Z has gained a well-earned reputation as one of Colorado’s leading roofing companies by providing first-rate workmanship and honest customer service. Contact our attentive team today for a free estimate on your next roofing project.
To learn more about metal roofing, be sure to read the A to Z Guide to Commercial Metal Roofing.