How to Install Metal Roofing Over Shingles

Have you been thinking about installing a metal roof on your home or business? Typically, a roof starts with shingles but did you know that you can actually just install the new metal roof on top of the shingles? The answer to the question of how to install metal roofing over shingles has many advantages, among them are:

  • A metal roof reduces cooling costs during the summer months because it can reflect the sun’s rays
  • Winter heating costs may be reduced thanks to a double layer of insulation
  • It’s the simplest and fastest way to install a metal roof.

Installing a metal roof on top of shingles can be done in three basic steps, only 2 are required. Please contact us for help in determining the best option for your home or business. The steps are as follows:

1) Remove the Shingles before Installing the Metal Roof

This step is not required, but complete removal of the old shingles will allow your contractor the best opportunity to determine the condition of the plywood or OSB board under the shingles and tar paper and whether it needs to be replaced. If you want to quickly install your new metal roof on top of the shingles, you must do so on undamaged shingles. If the shingles and plywood are damaged, then they should be removed and properly replaced.

Removing shingles before installing a metal roof is the best way to see the condition of the entire roof structure. Important inspections and repairs can be performed so that you do not have to perform them later and your chance of a leak is much lower. If there is a leak in your roof, it is important to remove the shingles and repair the damage completely.

2) Install Underlayment Right Over the Shingles Before Installing the Metal Roof

For a quicker, cheaper, albeit less thorough job, we can install a metal roof directly over the shingles. In this case, evaluation of the roof structure will be done from the attic and on top the roof, but cannot be as thorough as if the shingles were removed. A metal roof should not be placed directly on top of the old shingles, instead, a substrate should be installed over the shingles first.

In order to avoid damage to the metal roof which can expand and shrink depending on the temperature, there must be a protective barrier between the shingles and the new metal roof. The substrate that is laid over the shingles must be undamaged as well and greater care must be taken when installing it on top of shingles. This substrate base provides leak protection and increases the efficiency of your new roof.

3) Install 1×4 Purlins down over the Shingles before Installing the Metal Roof

With a good base, purlins or battens can then be installed to obtain a uniform surface that is ideal for installing a metal roof. The metal roof is fixed to three-quarters of the purlins and to half of the plywood, which increases the strength of the entire roof structure. If the base plywood or OSB board of your roof is in good condition, then the installation of the metal roof is done by applying 1×4 purlins directly over the shingles that have been covered by the layer of substrate. Installing a metal roof in this way gives you additional insulation that will protect you from all external influences. Also, a layer remains open between the shingles and the metal roof to allow for better airflow and less possibility of moisture building up between the layers and causing mold, freezing and thawing, and ultimately a leak.

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We hope this article has been helpful. We encourage you to read more about what we do and ultimately reach out to us to help you with your exterior remodeling project. Someone will be in touch very soon if you fill out the contact form on our homepage right here.