If you are upgrading your asphalt shingle roof to a metal roof, you may be wondering if the old shingles must be removed first. The short answer is no, as it is possible to install metal over old shingles. This guide can help you better understand how this works. 


The main benefit of installing over your old shingles is in cost. There won't be labor fees for the removal or disposal fees for discarding the old shingles. This can greatly reduce the cost of replacing your roof, especially on larger roofs that require more labor and greater disposal. There are also additional materials costs for some of the underlayment that is necessary once the shingles are removed.

Another benefit is time. It takes time to tear down an old roof and install all new underlayment for the installation of the new metal roof panels. Depending on the size of your roof, using the shingles as underlayment can reduce the installation time by one or more days.


There are some drawbacks to leaving the shingles on. Sometimes shingles camouflage damage to the roof decking below. Once the metal roof is on, it is harder to repair the decking if a leak does turn up. It's best to only leave the shingles after a thorough inspection is performed to make sure there is no hidden damage.

Weight can also be a concern. Most roofs are rated to hold the weight of an asphalt shingle roof along with any snow load requirements for the region. Metal roofs are lightweight, but they do have an impact on the overall weight of the roof. If your roof isn't rated to hold the weight of the shingles and metal combined, you may need to have the support structure shored up before installation.

Preparation and Installation

Preparation is fairly straightforward. It begins with an inspection to find any damage. Minor damage to decking can be repaired, but major decking damage means the roof must be torn down to the trusses and the asphalt shingles can't be reused. The shingles need to be in decent condition but some damage is okay as long as there is no moisture or active rot in any of the materials.

A layer of roofing paper is installed over the shingles once all small repairs are made. Then, the new metal roofing panels are installed over this underlayment. Everything is flashed and sealed afterward.

Contact a roofing installation and replacement service to learn more about your roof material options.