If you have an asphalt shingle roof that's showing its age and needs to be replaced, you can save time and money by adding a second layer of shingles over the existing ones. Adding a second layer of shingles to an existing roof is called a roof overlay, and it's a much quicker process than tearing off the existing shingles in order to replace them. In addition, the second layer of shingles will shield the existing shingles from sunlight, which helps them last longer until they finally break down. To find out how to know if your roof is a good candidate for an overlay, read on.

Your Roof Deck and Roofing Felt Are in Good Condition

An asphalt roof consists of three layers: the wooden roof deck, water-resistant roofing felt, and the asphalt shingles. When you overlay a roof, the only thing that's added is a new layer of shingles. They're nailed directly to the existing shingles. This means that your roof will continue to use your existing roof deck and roofing felt. As a result, they need to be in good condition if you want a roof overlay.

If you've had a roof leak that has gone unnoticed for a long time, rain may have leaked in and saturated the roofing felt or the roof deck. This weakens the roof deck and makes your roof more prone to collapsing under the weight of the shingles. Before you overlay your roof with new shingles, a roofing installation service will need to inspect the condition of your roof deck and roofing felt to make sure that they're completely dry.

Your Existing Shingles Aren't Curled

As asphalt shingles age, some of the volatile organic compounds in the asphalt will escape into the air. This makes the asphalt more brittle and causes it to shrink, which can result in an asphalt shingle starting to curl up at the edge that's not nailed to the roof.

If your asphalt shingles are starting to curl, your roof won't be able to support an overlay. The edges of the new shingles would rest on the curled portion of your existing shingles, and that would create a gap that rain can use to enter your attic.

Your Home Can Support the Weight of the Extra Shingles

While asphalt shingles aren't the heaviest type of roofing shingles in use, they still weigh a considerable amount. Not all homes will be able to support the weight of an extra layer of shingles. Before you can overlay your roof with new shingles, you'll need to hire a structural engineer to inspect the roof support in your attic. A structural engineer will calculate if your home will be able to support the weight of adding a new layer of shingles to your roof.

If your roof is a good candidate for an overlay, it's a good way to make installing a new roof quicker and less expensive. It eliminates the labor and disposal costs associated with tearing off an existing roof. To find out if your roof can support an overlay, call a roofing installation service in your area and have it inspected. Based on the condition of your existing roof, they'll be able to tell you if an overlay will be a suitable option.