Pros and Cons of Getting a Roof Over Existing Roof or Re-Roof

Pros and Cons of Getting a Roof Over Your Existing Roof or Re-Roof

Need a new roof on your home but are being bombarded by advice and options? Getting a new roof installed on your home is a major home improvement project and one that can costs thousands of dollars. There are ways to save money on the roof installation that many roofing contractors will offer you and the biggest way to save money is by re-roofing your home. Re-roofing your home is basically getting a roof over existing roof and placing a new layer of roofing materials on top. While this process can save money and time when it comes to getting a new roof it may not be your best option. Here’s why…

Pros and Cons of Getting a Roof Over Existing Roof or Re-Roof

A project that many home owners face only once or twice is getting a new roof installed on their homes. Most roof shingles are designed to last a long time. In fact, even low quality roofing materials such as three tab shingles can have a warranty of 15 years. Some of the higher quality products and metal roofing can last for more than 40 years.

Typically, when you get a new roof installed on your home you have two options. The first option is known as a tear off installation. A tear off installation of the roof means that all of the old roofing materials are removed or “torn off”, hence the name. The shingles on a roof and underlayment along with any sealants or roof boots that are installed are removed. The roof is basically stripped down to the wood decking below. Then, new roofing materials are installed.

The second type of roofing installation is known as a roofing overlay, re-roof, or roof over existing roof. The process is different than a tear off installation of existing shingles because the old roof is basically left in place and you get a new roof on top of old roof. Only a small amount of the old roof is removed and this is usually only around the edges and ridge of the home. This can include step flashing, drip edge, ridge vents, and more items. The roof is cleaned and swept off with brooms and any debris is removed from the roof and then a layer of roofing materials is placed directly over existing shingles of the old roof. Once the process is complete, you are left with a new roof with new shingles over the old ones.

Differences Between Re-Roofing Over Existing Roof: Roof Overlay Vs Tear Off

Differences Between Re-Roofing Over Existing Roof: Roof Overlay Vs Tear Off

As you can imagine the differences when it comes to reroofing and tear off installation can be huge. While both of these roof installation methods can leave you with a completely new roof that has a warranty attached there are some pros and cons to each. The biggest difference is usually price of the installation and if you’re on a budget, a roof over existing roof may be the best option for you. We’ll take a look at some of the biggest differences and pros and cons of each below:

What Are the Advantages of Roof Replacement Rather Than Re-Roofing

When you get a roof over old roof and the old shingles are left in place:

  • Re-roofing a home is less expensive. When you get a roof over existing roof installed you are eliminating a few costly components of roof installation. The first thing you’ll eliminate is the cost of labor to remove the old roof. Shingle removal can be costly especially for larger homes. Not only that but you’ll have much less debris in the project since you’re not removing the old roof.
  • Fast Installation of the New Roof. For the average size home a new roof installation can take a few days to a week. When getting a re roof on your home you may be able to get a new roof in under a single day.
  • Overall Appearance of the Roof is Good. The biggest concern that most home owners have when it comes to the re roofing project is the appearance after the roof is installed. Most re-roofs can look good but there may be noticeable differences depending on structural factors.
  • You Still Get a Warranty. Most roofing material manufacturers will provide a warranty on their products for the roof install even if the roof installation is a roof over existing roof. In order for the warranty to be honored however, the project must still be done according to local building codes and manufacturers specifications.
  • Two Roofs are Better Than One. Well maybe… Some people think that an additional layer of roofing is better when severe weather strikes such as tornados, hurricanes, or blizzards.

When you get a roof tear off installation:

While there are many advantages of getting a roof over existing roof there are also a few drawbacks. Here are some reasons why a tear off roof installation may be your best option: 

  • Your Home Has Already Been Re-Roofed. Installing a single layer of roofing over the old one can be a good idea, but more than two can be dangerous. Since shingles weigh so much, adding that much weight to the roof of your home can make if unstable and cause a collapse. Most building codes will only allow two layers of roofing, anything more is simply too much. So if you already had a roof over done on your home your only option may be a tear off installation.
  • Major Problems with Your Current Roofing. Having a uniform surface for the new roofing to be placed on is important. If the shingles on your current roof are in bad shape with missing, torn, or curling shingles it may make the overall look of the roof undesirable if a roof over is done. Small areas can sometimes be patched but if the patches to make the roof uniform are widespread the roof over existing roof may not save you any money at all.
  • You Have a Leaking Roof Now. Roof leaks, no matter how small can cause damage to the inside of your home. Not only that but the roof decking under the shingles can be damaged by a roof leak. This roof decking will need to be replaced before getting a new roof installed and if you’re getting a roof over existing roof it may not be. Instead, if would just be covered up again leaving your home more vulnerable to future problems in that area of the roof.
  • Roof Overs Add Lots of Weight to the Home. A single shingle doesn’t seem to weigh much but when you consider your roof may be comprised of thousands of shingles the weight of the roofing materials can add up. When you re-roof your home you basically multiply that weight by 2. For older homes which are not designed to handle this much weight it can cause a lot of problems. Foundations sinking, structural collapses, and more. Most roofing contractors will examine the attic and determine if re-roofing is a viable option for you.

What Are the Long-Term Effects of Getting a New Roof Over for your Home

When you get a roof over installed on your home you will basically have a new roof installed on the home. Sure they may be differences in the method of installation but your roof should still protect the home from weather and the elements. There may be long term consequences of getting a roof over for your home however. The long term effect of getting a new roof over existing roof is the weight that it puts on the home and how it affects the home. Having a foundation that sinks a bit from the overall weight can cause drywall to crack and doors not to shut properly. There may also be cracks in the foundation of the home as well which would need repair.

Can you Install Architectural Shingles Over Architectural Shingles

Can you Install Architectural Shingles Over Architectural Shingles

With roofing, there are many choices when it comes to roof coverings. One of the most popular types of roof covering is asphalt shingle roofing. Even then there are many different styles, designs, and manufacturers. The two biggest types of shingles are three tab shingles which are a flat shingle with one layer of material and the other is architectural shingles which can have a few layers of materials used in manufacture. These additional layers give the shingles more depth and can look great once installed.

You can get a re-roof done on your home if it currently has architectural shingles installed in some areas. However, some building codes only allow a roof over if the underlying shingles are three tab shingles. Be sure to consult with local building codes about your home. This is due to the added weight of three tab shingles versus architectural shingles. Having two layers of architectural shingles is like having 4 layers of three tab shingles.

Installing a thicker shingle over the old roof does have it’s advantages however. The thicker the top layer of shingle the more imperfections it will hide.

Some May Ask: Can I Shingle Over Moss Covered Shingles

Some May Ask: Can I Shingle Over Moss Covered Shingles?

When you get a roof over existing roof you basically cover up everything on the existing roof. One of the biggest concerns that home owners have when they do this is they have algae or moss growing on the existing roof. Many times the roof will be cleaned and the algae or moss removed prior to getting a roof over done. This may include pressure washing the roof in some cases, but it’s usually not needed. You may also opt for algae resistant shingles for the project which can help to prevent the algae or moss from returning on the new roof.

Warranty Concerns When Getting Re-Roofing Over The Existing Roof

Getting a new roof means that you’ll have peace of mind because the roof will be covered by a warranty. Many people think that the warranty will not be honored if the shingle roof installation is a roof over or re-roof. This usually isn’t the case. For most of the major manufacturers such as GAF, Owens Corning, and more will still warranty the roofing materials if they are installed correctly.

So Should You Get a Roof Over Existing Roof?

When considering what type of roofing installation you’ll get it’s always best to weigh the benefits of each. While both a roof over existing roof and a tear off have their advantages, for most home owners the decision comes down to price. Depending on your budget, either of these methods can leave you with a new roof. It’s always best to talk with a licensed and qualified contractor in your area. Be sure to fill in the form below to get a quote on your roofing project. You can also visit this link for a free quote.


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