It is possible to install new shingles directly over old shingles. This process is known as re-roofing, and it is not ideal for most homes. Let’s explore the pros and cons of re-roofing and why we advise against it.
What Is Re-Roofing?
With traditional roof replacement, the existing shingles are removed before new shingles go onto the roof. This allows the roofers to inspect the underlayment and create a pristine finish for the new roof. With re-roofing, the new shingles go on top of the existing layer of shingles with little to no demolition. This has the potential to save time and money upfront, but it could lead to costly issues later on.
Pros of Re-Roofing
The biggest benefit to re-roofing is that it is faster and less expensive than roof replacement. It’s the same concept as painting over wallpaper. The lack of demolition speeds up the process, but it doesn’t necessarily yield the same results.
Cons of Re-Roofing
The downsides of re-roofing greatly outweigh the benefits. Here are some reasons you shouldn’t put new shingles over old shingles:
- Re-roofing is not an option for many roofs. If your roof already has multiple shingle layers, local building codes will likely prevent you from re-roofing.
- A new layer of shingles adds to the weight of your roofing. The plywood underneath is only so strong. Putting extra pressure on it may lead to problems in the future.
- Without removing the shingles, it’s nearly impossible to inspect the structure below. During roof replacement, we can replaced damaged plywood and create a sturdy structure for the new roof. An oversight during the re-roofing process may cause you to put new shingles over a bad foundation.
- Shingles are not designed to be installed over other shingles. They’re made for flat surfaces. This means that they may not provide a sufficient seal when installed over the old shingles.
- Your existing shingles may not be a good footing for the new shingles. If they are starting to crumble or fall off completely, the foundation below your new shingles will be unreliable.
- Your new roof may be prone to ice dams. This is because there is no way to install an ice-and-water shield during a re-roof.
- Re-roofing could void the warranty on your new roof, or it may impact future home inspections. The effects will vary based on the situation.
- Not all roofing materials support re-roofing. If you have slate shingles, cedar shingles or a metal roof, you won’t qualify for re-roofing.
- Roof replacement lasts significantly longer than re-roofing. If you want to maximize your return-on-investment and save money in the long run, roof replacement is the way to go.
You Can Put New Shingles over Old Shingles, But You Probably Shouldn’t…
Just because re-roofing is an option for your home doesn’t mean you should consider it. The fact is, whatever time or money you may save upfront is only going to be temporary. When you need a new roof in the new future, it will require even more demolition than your current roof will. If there is undetected water damage or issues with your underlayment, the costs are going to add up quickly. You’re better off getting the job done right the first time so you can enjoy your new roof for decades to come.