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When It Is Not Appropriate to Layer Roofing Shingles

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When doing a home improvement project, many homeowners wonder what they can and cannot get away with. Sometimes the shortcut is to save time, but it also can be to save money. When it comes to installing shingles on a roof, you have the option of layering them on top of old shingles, or ripping all the shingles off and starting from scratch. Here are some reasons why you cannot layer your shingles.

Potential Legal Problems

Before you begin a roofing project, always check with your city to see what the building codes require for the job to be done properly. There could be a limit to how many layers of shingles are allowed on a roof. If you have installed more layers than what is allowed, you will be required to rip your entire roof off and start from scratch. This will create a more costly and time consuming repair than if you simply followed the rules in your local area.

A good rule of thumb is to stick to at most two shingle layers if you are not bound by any building codes. National codes, such as the Two-Family Dwelling Code, limit a roof to three layers of shingles. However, some cities like Minneapolis require all existing roofing materials to be removed when installing a new roof.

Old Shingles That Curl

Shingles that are old and curling upward on the roof will cause problems when it comes to layering additional shingles. This is because the old shingles won't allow the new ones to lie flat. It increases the risk of getting water beneath the new layer of shingles, defeating the whole purpose of installing them.

Roof Rot

If your roof deck has signs of premature rotting, it will require ripping off the original shingles to correct the problem. If left alone, moisture will remain trapped under the shingles and cause more damage.

Pre-existing Roof Bowing

When your roof starts to bow, it is already having problems holding the weight of the shingles. Adding more weight in the form of an additional layer of shingles is just going to make the problem worse. Adding an additional layer of shingles may cause decking and joists to need re-bracing as well.

Installing a brand new roof will be a big home improvement cost for you as a homeowner. Make sure you do not make the mistake of putting on too many layers of shingles, as it could cause damage to your home.


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