Can You Put a New Roof on Top of an Old Roof?

Most homeowners want to know if it is possible to put a new roof over an old one. The answer is Yes. You can put new shingles over existing shingles that are in good condition.

However, you can only install new shingles over asphalt shingles that meet the re-roof conditions. Also, you cannot mix materials; for instance, you cannot install shingles over wood tiles or slate.

The process of installing a new roof over an old one is called re-roofing, while tearing off the old roof to install a new one is called roof replacement. However, there are several conditions and factors a roofer will consider before undertaking a re-roof.

So, you will learn when a re-roof is possible, when you should not re-roof, the benefits of re-roofing, and the disadvantages of re-roofing.

When Can You Put a New Roof Over an Old One

As a homeowner, you may not understand the roofing dynamics. Choosing a re-roof over a roof replacement can only be recommended by a certified roofing contractor like Roof Master. Rest assured that you will receive quality roofing services.

Re-roofing is cheap, faster, and convenient compared to roof replacement; however, it has its limitation and can only be done under given conditions;

  • A re-roof is a good option if your roof is at the end of its life, but the underlying elements and the sheathing board are still in good condition.
  • If your shingles are losing granules, they are worn out due to age but are not causing leaks.
  • If your shingles are not curling or missing
  • If you want a different roof colour or design

When You Should Not Put a New Roof Over an Old One

A thorough roof inspection should precede any roof installation. The roof inspector will determine whether your roof is suitable for a re-roof or a roof replacement.

Also, you will get a roof inspection report that will have recommendations on whether your roof is suitable for a re-roof or you should consider tearing it off.

Some of the reasons why your roof might not be suitable for re-roof include;

1.            When You Do Not Have Asphalt Shingles

The most straightforward reason your roof can not qualify for a re-roof is when you don’t have asphalt shingles. A re-roof is only possible if you have shingles since you can only place shingles over shingles. Besides, you cannot mix materials or install a new layer of shingles over wood tiles or slate.

2.            When There Are Curling and Missing Shingles

You can only install a new roof over an old one if the old roof is completely flat and level. Several factors might cause the existence of curling shingles; therefore, it is advisable to involve a professional roofer to determine the cause and replace the shingle before proceeding to a re-roof.

3.            If Your Roof Has Two Layers of Roof

Any time you install a new roof over an old one, you add more weight to the roof. Besides, most building codes will only allow two layers of the roof to your house. So, if you have already done a re-roof, your only option will be to tear off the roof to install a new one.

4.            Local Building Codes

While most building codes allow a maximum of two roof layers, some local codes do not allow multiple roof layers. So, you can only install a single layer of the roof.

Benefits of Putting New Roof Over an Old One

1.    It is cheap

Tearing off an existing roof is not only time-consuming but also expensive. The roofers will take a day or two to tear off the roof and then several days to re-install the new roof.

However, re-roofing involves installing a new roof on the old roof; therefore, there will be no tearing off costs.

2.    Faster Installation

Re-roofing involves installing the new roof over the old one—no tearing off involved. Naturally, the task will be easier, and the installation will be quick.

3.    Extra Protection

A new shingle layer is added to an existing old layer, making the roof stronger and more protective. The roof acts as added insulation and prevents moisture from getting into the house.

4.    It Is Convenient

The re-roofing process does away with tearing off, saving time, money, and is less messy. Besides, you don’t incur the disposing cost of the materials torn off from the roof.

The Disadvantages of Installing a New Roof Over an Old One

1.            Warranty Violation

Every manufacturer has its unique warranty conditions. So, before you re-roof your house, counter-check the manufacturer warranty conditions. Some manufacturers will not accept warrants on new shingles installed on old shingles.

2.            Re-roofing Add Weight to Your Roof

An additional layer of shingles will add more weight to your roof since shingles weigh between 350-450 pounds per square. So, if your roof was designed to hold one layer of roof, you are probably overloading it with a re-roof.

3.            No Visual Inspection on the Sheathing Boards

Re-roofing will not involve a tear-off; therefore, the roofer will not see how the decks look. The roofer has to do a ‘walking inspection’ to identify spongy spots and problems on the roof and fix them before undertaking a re-roof.

An average roofer might miss some spots and go ahead with re-roofing, which might cause problems in the future.

4.            Problems When Fixing Leaks

A new roof layer over an old one will complicate the roofer’s effort to fix a leak. The roofer has to undertake thorough checks to identify the problem and fix it entirely.

5.            It Is Difficult to Replace Underlayment

A re-roof does not offer room for replacing underlayment. A good example is the roofing paper installed between the sheathing and the shingles. If it wears out, the roofer can’t replace it and can lead to water intrusion in the future.

Final Word

When choosing a re-roof over a roof replacement, you must consider several factors to enjoy the long lifespan of your roof. To be on the safe side, engage a professional roofer to undertake roof inspection and give recommendations. That said, re-roofing can save you money, time and can be convenient compared to a roof replacement.