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Problems With Installing Metal Roofs Over Shingles

1 February 2023 by Leslie Turner

Installing a new metal roof is expensive, which is why many homeowners try to minimize installation costs. One way of doing this is installing the metal roof over the asphalt shingle roof. Although this may work in certain circumstances, there are cases where it isn't advisable. Here are the dangers of installing metal roofs over shingles.

Roof Leaks Are Hard to Track

When you place a metal roof over a leaky asphalt roof, you don't address the leaking problem. When water passes under the metal panels, it moves down to the old shingle roof. Over time, the water will reach problem areas and begin to penetrate inside your home. 

Since these leaks are from different parts of two different roofs, tracking the source will be difficult. This is one of the reasons you should check the condition of your roof before re-roofing. If there are any issues, ask your metal roof contractor to fix them before installing the metal roof over the shingles.

Replacing Roofing Components Is Impossible

Replacing your roof gives you a chance to remove old roofing components and materials that are worn out. However, when you install metal roofs over shingles, you bypass the tear-off process.

Although this will save you money, you fail to replace materials that shouldn't be on the roof, like underlayment. This is the protective layer installed over your roof's decking. When you install a metal roof over asphalt shingles, you won't remove the underlayment from the old roof. This means you will not get the underlayment designed for metal roofs. This will reduce the longevity of the roof.

Non-Compliance With Building Codes

In some areas, installing a layer on top of an existing roof isn't allowed. If you were to install a metal roof over asphalt shingles, you may be subjected to hefty fines for going against building codes.

Furthermore, you will incur additional expenses for removing the metal roof and old asphalt shingles and installing a new roof. However, some areas allow re-roofing with different roofing materials. Before you begin re-roofing, ask your contractor to take you through your area's building codes.

Warranty May Be Voided

Most roofing manufacturers offer warranties for their roofing materials. If anything happens to the roofing materials during the warranty's timeline, they will supply you with new materials at no additional cost. However, your metal roof warranty may be voided if you install the roof over asphalt shingles. Therefore, ensure you know the warranty conditions before beginning the re-roofing project.

To have a professional take care of your roof installation or repairs, contact a professional roofing contractor in your area.

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