How Many Layers Of Shingles Can Be On A Roof?

Jessica Allen
by Jessica Allen

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.

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Is It Okay To Overlay Shingles?

Overlaying shingles is a somewhat common practice, but it’s generally not recommended. There are several issues that can come up when you overlay shingles.

Potential Problems

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 Upside

Still, there is one main benefit to overlaying shingles rather than tearing off the existing ones and replacing them. You can save some money in the short term. However, many professionals argue that overlaying shingles will end up costing you more long-term.

Overlaying shingles also creates less of a mess, and it’s a quicker project compared to a full roof replacement.

How Many Layers Of Shingles Can You Have On A House?

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.

Why Are Multiple Layers Of Shingles Bad?

There are several reasons why multiple layers of shingles are typically considered a bad idea.

Impossible To Detect Damage

Multiple layers of shingles eliminate the opportunity to inspect the roof’s sheathing. This means you won’t be able to see bad flashing, damaged or rotting wood, leaks, algae growth, and other problems. Since roof problems generally need to be addressed immediately before they cause notable damage to your home, this is problematic.

Installation Issues

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.

Building Regulations

Depending on where you live, multiple layers of shingles may go against local building codes. Some areas allow for two layers of shingles, and some only allow one.

Added Weight

When you add another layer of shingles to your home, you’re basically putting on a second roof. The weight that comes with additional layers of shingles puts stress on the decking. This can be a major problem, particularly in areas that get a lot of heavy rain and snow.

Warmer Home

With multiple layers of shingles, heat gets trapped between them. Not only can this age your shingles prematurely, but it can make your home warmer. In turn, this can make your air conditioner work harder and increase your cooling bills.

Negative Inspection Reports

If you plan to sell your home in the future, multiple layers of shingles will affect your inspection negatively. Your home will likely have less value than a similar home with a single layer of shingles on the roof.

Voided Warranties

In some cases, putting more than one layer of shingles on your roof can void your roof warranty. Be sure to read the fine print to see if this voids your manufacturer’s warranty.

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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.

Jessica Allen
Jessica Allen

With a lifelong passion for writing plus strong enthusiasm for home improvement and DIY projects, joining the team at Upgraded Home was an easy choice. Jessica Allen likes to share helpful information with current and aspiring homeowners. Aside from writing, Jessica loves doing yoga, playing the piano, and dabbling in graphic design.

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