How Many Layers Of Shingles Can Be On A Roof?

If it’s time to replace your roof, you may be wondering if there’s a less expensive solution. Layering shingles is an option, but is it a good one? And how many layers of shingles can a roof handle before they cause more harm than good?

Most local building codes allow for two layers of shingles, but overlaying shingles can cause a variety of roof problems. It makes it impossible to check for damage, stresses decking, increases cooling bills, and can void your roof warranty. It’s recommended to remove and replace the existing shingles, but layering can be cheaper and quicker in the short term.

Read on to learn more about whether it’s okay to overlay shingles. We’ll also discuss how many layers of shingles you can have on a house. Then, we’ll cover why multiple shingle layers are generally thought of as a bad idea.

First, multiple layers of shingles make it impossible to examine the decking beneath them. Therefore, there’s no way to check for and address underlying damage. This can lead to leaks, water damage, wood rot, mold, mildew, and other problems.

Another issue is that it’s very difficult to install a second layer of shingles correctly. It’s important for shingles to lay flat, and when you have more than one layer, that becomes quite a challenge. It also adds a lot of weight to your roof, potentially more than your roof was designed to handle.

The number of shingle layers you can have on a house varies depending on the state you live in. Most states’ building codes only allow for two layers of shingles. However, you’ll still come across some houses that have as many as four layers of shingles.

Some professionals state that any more than three layers of shingles is too much. But generally, if you hire a professional contractor, they’ll recommend a full replacement if you have more than two layers.

When shingles are first installed, you have a smooth and flat surface to work with. That’s not the case when adding additional layers of shingles. Since the new layers are built on top of existing shingles, the surface is bumpy and filled with gaps.

This type of surface makes it challenging to mount the new shingles securely and accurately. It’s also extremely difficult to install flashing properly on the second layer of shingles. Improperly-installed flashing makes your roof more prone to leaks.

Related Questions

How can you tell how many layers of shingles are on a roof?

A roof with multiple layers of shingles will often look lumpy and uneven from the ground. This will be especially noticeable at roof penetrations like gas appliance flues and plumbing vents.

Another option is to get up on a ladder and look at the shingles at the edge of the roof. A normal roof will have two layers: a starter row of shingles, and one layer of shingles on top. But you’ll be able to see four total layers if you’re looking at a roof with two layers of shingles.

Can you put a third layer of shingles on a roof?

While putting a third layer of shingles on a roof is technically possible, it usually goes against building codes. A third layer of shingles also comes with a host of potential problems. These range from not being able to see any damage to the decking, to voiding the roof warranty.

There’s also the problem of adding more weight to the roof than it can handle. Multiple layers of shingles can even make your home warmer and drive up your cooling bills. If you want to sell your home, three layers of shingles will also negatively impact inspection reports.