How Many Layers of Shingles Can Go On a Roof?

When you notice shingle damage on your roof, you may wonder if you will soon be footing the bill for a full roof replacement. While a roof replacement is sometimes required, adding a second layer of shingles over the damaged portion (also called an overlay or a layover) can be a viable option in some situations.

Adding roof layers is not always the right move, so it is important to consider your specific situation carefully before you make a decision. Find out how many layers of shingles are allowed on a roof and when you should just replace your roof instead.

How Many Layers of Shingles Can You Put on a Roof?

At maximum, you can install two layers of organic or fiberglass asphalt shingles for roofs with up to an 18.5-degree pitch. (This roof pitch, which refers to a roof that rises four inches for every foot, is fairly standard for residential roofs.) Any more than two layers of roof shingles adds too much weight.

Some local building codes do not allow overlays at all; in those municipalities, you can only have one layer of shingles. It is always a good idea to review any applicable building codes before you launch a repair or renovation project.

When Should You Consider an Overlay?

Your roof is an important component of your home. It adds to curb appeal and protects you and your family from the elements. So, when it is time for a repair, you will want to take care of it as quickly as possible.

If you are considering adding a second layer of shingles to your roof, know that it is not the best option for all situations. Here is a look at when an overlay could be the right option for you:

• The roof itself is not damaged or rotten.

• The damaged shingles are contained to one section of the roof.

• The majority of the roof is not in need of new shingles.

• An overlay has not yet been done on the roof.

Shingle damage often happens when you experience high winds or damage from falling trees or branches. If general wear and tear or weathering has occurred across your whole roof over many years, an overlay is likely not a good option. 

Benefits of Adding Another Layer of Shingles

The benefits of adding a roof overlay include cost and time savings. Since an overlay involves roofers simply putting a new layer of shingles over old ones, they do not have to remove existing shingles. This means a quicker job time and much less cleanup. Because it takes less work to do an overlay compared to replacement, it saves money in labor costs.

What to Know About Nailing Over an Asphalt Roof

There are a few things you should know before deciding to move forward with nailing over an existing asphalt roof.

Flashing Condition

During an overlay installation, your roofer cannot properly inspect the condition of your flashing because they are not ripping up the original roof layer. If there are any bad seals or damage to your roof flashing, you will not know about it until you have roof leaks.

Typically, damaged flashing leads to problems like damaged shingles and water inside your attic, ceiling, and walls. If your roof has not given you any issues in the past, there is a good chance your flashing is in decent shape; but realize that it is a bit risky, since you cannot notice leaks unless there is rainy or snowy weather.

Risk of Roof Decking Issues

When you opt for a full roof replacement, the roofer has a chance to inspect the decking before installing the new shingles. But during an overlay installation, your roofer has no idea if your roof decking is in good shape or not. So, in a worst-case scenario, you may end up with roof leaks. If this happens, you will be back at square one, except this time, you will likely need to pay for a full replacement of both your roof and decking.

Overlay Shingle Type

When installing an overlay, your roofer should use the same type and size of shingles as your existing ones. This will ensure that your new layer will lie as flat as possible to avoid leaks.

Considerations Before Adding a Shingle Overlay

Before adding another layer of shingles to your roof, you should ask yourself some specific questions. 

What Does My Warranty Say?

Before adding a second layer of shingles, you should check your roof warranty to ensure that this sort of repair will not diminish or void it. If adding an overlay is incompatible with your warranty, you may need to choose between replacing your roof and diminishing or voiding your warranty. 

Will the Extra Weight Damage the Roof Underneath?

While shingles do not weigh a lot on their own (most asphalt shingles weigh between two and three pounds per square foot), that weight can add up quickly when the roof underneath is damaged. 

Additionally, second-layer shingles are often designed to weigh more, since they have to disguise any higher points or depressions from broken or missing shingles. The fasteners used to secure the shingles, like staples and nails, also need to be longer and heavier since they must reach through multiple layers. 

If your roof is already weak or damaged, this extra weight can put undue stress on your roof and structure. This can lead to movement and settling of the house, which may cause cracks in the foundation and walls. 

As you consider whether your roof can withstand the extra weight of a second layer of shingles, you need to think about the following:

• Does your area get lots of snow and ice, which can add to the overall weight resting on the roof? 

• Is the roof underneath the damaged shingles in good shape and free from damage?

• Has a professional roofer in your area assessed the weight that your roof and structure can withstand?

Will I Need to Replace My Roof Fully in the Near Future?

Eventually, all roofs need to be replaced, so if you know that you will need a replacement in the next couple of years, choosing a complete replacement now instead of an overlay may spare you from paying double (overlay plus roof replacement) in the long run. Keep in mind that, when it does come time to replace your roof, removing a double layer of shingles will cost more than removing a single layer.

How Much Does a Shingle Overlay Cost?

The cost of adding a shingle overlay will depend largely on how much area you have to cover and which product you are installing. On average, the cost to repair a roof, including materials and labor, is around $1,000. 

Replacing a roof entirely tends to be much more expensive than adding a second layer of shingles. Depending on the size of your roof and the materials you choose, you can expect to pay an average of $14,000 for a new roof.

Adding an overlay or completing a full roof replacement can improve curb appeal and keep you feeling safe and secure at home. The right roofing contractor will be able to talk you through the pros and cons of each option and give you the information you need to make a good decision. 

Can I DIY a Shingle Overlay Project?

While it can be tempting to save some money and handle the project yourself, you should always call in a pro to work on roofing jobs. Working on roofs requires expertise and experience to ensure it is done correctly and safely. It is advisable first to get a roofing inspection from a professional and then, if they give you the green light, move on to hiring a roofer near you for your project.

When to Consider Re-Roofing

Now that you have looked at the ins and outs of roof overlays, it is time to find out when re-roofing is a better choice.

Your Roof’s Age and Condition

If your roof is nearing the end of its lifespan, you should strongly consider going with a full re-roofing rather than an overlay. Even though it is a bigger financial investment, it is a sound choice. You will not have to worry about hidden issues with your roof decking, nor think about another roof replacement for decades. You should check the lifespan of your roof, according to the type of roof shingles you have.

You should also consider the condition of your roof. Have you repaired it in the past, or has your roof been problem-free? If you have neglected to do regular maintenance, then there may be existing roof damage that you need to fix. And if your shingles are damaged, then you should go with re-roofing to avoid issues down the road.

Your Roof Decking’s Age and Condition

You should replace roof decking every 20 to 30 years, so if you are nearing the end of its lifespan, you should avoid installing an overlay. If you have had roof problems in the past, such as leaks, then your decking could have moisture problems like wood rot. In these cases, it is much better to opt for a re-roofing job. If your roofer finds damage to the decking, you will have the opportunity to replace it before they install your new shingles. In the end, you will have a solid, leak-free roof that you can count on, even in severe weather.