As a roofing professional, you likely field questions from curious homeowners from time to time. One of the trickier questions—because there isn't a definitive answer—is: "Can you put new shingles over old shingles?" The answer to this will depend on certain factors, and you can only provide a firm "yes" or "no" after inspecting an individual's roof.
So the short answer is: yes, it's possible to install new roof shingles on top of existing ones. But . . . specific conditions must be met and the following considerations must be taken into account:
Local Codes and Roof Condition Considerations
First, you need to understand your local building codes. In most jurisdictions, the code won't allow more than two layers of roofing on a home. If the home already has two layers, a complete tear-off is in order. If it has only one existing layer, the roof may be a candidate for a second layer.
The existing roof's condition will also help determine if a shingle-over-shingle installation is possible. If shingles are weathered, warped, or curling, they aren't suitable to be shingled over. New shingles require a smooth surface for proper installation and performance.
Also, consider whether the homeowner is replacing the roof because they've experienced extensive leaking. In this case, putting new shingles over the existing ones may not be wise. Water damage to the deck or mold issues might be left untreated if they remain hidden under the existing roof.
Risks of Putting New Shingles over Old Ones
A shingle over shingle installation can be appealing to homeowners due to lower costs and faster installation time. But it's important they understand the potential risks. For instance, you'll likely have to explain that a roofing system is composed of many parts that work together to provide protection for their home. Many homeowners think of a roof as only what they can visibly see—the shingles.
GAF brochures can help with the education process. For example, the GAF Timberline HDZ® brochure includes diagrams that identify each layer of the roofing system, which can help homeowners understand how each one is necessary to achieve a roof's peak performance.
Benefits of a Tear-Off and Replacement
The next time you're asked, "Can you put new shingles over old shingles?" you'll be able to respond with some solid answers about the pros and cons. To give the homeowner a complete picture, you should also share the benefits of a complete tear-off and replacement, so they can understand their options and make a cost-benefit calculation.
Here's a look at a few advantages a total replacement offers:
- A tear-off allows the contractor to inspect the wood deck's condition and determine if repairs or new OSB board are needed to ensure it's structurally sound.
- Tearing off the roof's old layers can help ensure the new system has a solid, smooth surface for optimal performance.
- A total replacement allows an adequate leak barrier to be installed in critical areas, including rakes, eaves, valleys, hips, and around penetrations.
As a contractor, it's important to guide the homeowner through their decision-making process to help them find the best solution for their individual circumstances. To gain access to the tools, trainings, and resources that make this easier and to offer enhanced warranty systems to your customers, become a GAF-certified contractor.
