Tear Off Existing Shingles or Add a Second Layer

One of the early decisions that needs to be made on a roof replacement project is whether to leave the existing roof and install the new roof over it, or tear off the existing shingles prior to re-roofing. While this is not a complicated decision there are a few considerations a homeowner needs to keep in mind when working on their own roof. When using a roofing contractor these things also need to be discussed, but since the contractor clearly understands all the variables, he’ll make his recommendation based on these same criteria.

The most obvious question to consider is whether your roof already carries a second layer of shingles. Most roofs can structurally support two layers of asphalt shingles and occasionally on older homes you may find a third, but in some places local regulations may prohibit a third layer.  If your roof only contains one layer, you need to make sure your roof will carry the additional weight. This involves evaluating the roof joists and trusses to make sure they are close enough together and the correct type for adding a second layer. If they’re more than 24” apart on center you should remove the existing layer to prevent potential sagging. Anything less than 24” is probably OK for the additional layer.

The other important consideration for adding a second layer is the overall condition of the shingles on the first layer. Since it’s necessary to provide a flat, well-prepared surface to receive the new roof felt and shingles, if there are a few curled or broken shingles they need to be trimmed prior to laying down the new roof felt. While you’re no doubt replacing the roof because the shingles are worn or need repair, if they’re too curled or wavy it may be better to remove them altogether.

If you’re removing the existing roof or roofing over it, it’s always best to replace the flashing. The condition of the existing drip edge will determine whether it gets replaced, but “new” always looks better. Even if you’re trying to roof as economically as possible, don’t take chances when these components are worn.

Whether you decide to tear off, or add a second layer of shingles, it will simplify your project if you identify and select components that are designed to work together. There’s an online resource that can help. At www.SelectYourRoof.com you can view asphalt shingles and other materials necessary to complete your roofing project. They’re manufactured to perform together as part of your roofing system; helping you make decisions necessary to keep your project on time and within budget.

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