Re-Roofing: Should You Put New Shingles Over Existing Shingles or Tear Off?

Reroofing

The process of recovering or replacing an existing roof covering.

Roof recovery

The process of installing an additional roof covering over an existing roof covering.

Roof replacement

The process of removing the existing roof covering, repairing damaged substrate (if required) and installing a new roof.

Reduced cost

As with just about any home improvement project, the biggest portion of the budget goes toward labor costs. It’s estimated, on average, that a roof project that does not require tearing off the old roof will cost about 25 percent less than a project that does require that extra labor. But the costs involved include more than just labor – you also have to consider the dumpster rental fees, as well as potential permit fees for renting a dumpster to place on your property or on the street.

Faster completion

While quality contractors do what they can to minimize noise and clutter, roofing projects come with plenty of both. This can be a hassle for some homeowners, which means having the crew on site for as short a time as possible is a big bonus. Rather than having to go through the din of a roof tear off, doing the overlay takes that out of the equation and the time to finish the project is about 25 percent faster.

Easier to manage

Planning the logistics of a roofing project is never easy, but when you take away the multiple steps involved with the tear out phase (dumpster permit, dumpster rental, drop off and pickup), you make the planning that much easier. Putting an extra layer of shingles on a roof rather than removing the existing layer(s) is something you should ask your contractor about.

Allows for thorough inspection

The typical roof has multiple layers that are covered by shingles. While the shingles might look a bit aged, the layers underneath could be in horrible shape. One of the only ways to thoroughly inspect a roof is to tear off the existing one. This allows inspectors to see every square foot of sheathing (usually .75-in. plywood) and determine if repairs or replacement is needed.

All-new material

Another reason a contractor might recommend to tear off the existing roof is that everything will be switched out with brand new material, which means you don’t have to worry about the layers beneath the shingles going bad on you anytime soon.

The option to upgrade materials

Roofing materials have improved over time, so if your roof is 20 or 30 years old, there’s a good chance the underlayment, which blocks moisture that gets through the shingles from touching your sheathing, is outdated and can be improved upon. Also, if the previous contractor cut corners and used subpar materials, this is a chance to make a big upgrade to more durable roofing materials.

Respond to climate conditions

Roofing material manufacturers have done plenty of research and design to come up with new products to fight all types of weather. They have also made improvements that can better protect your home against heat and cold. New materials give you a fighting chance against Mother Nature.

Longer lifespan

Asphalt shingles being produced today can have a lifespan of around 30 years. An old existing roof can still degrade, so if you are looking to maximize your new roof’s lifespan, choose the replacement option.

Lower maintenance

When you buy an old car with high mileage, you can expect a high amount of maintenance. It’s the same for old roofs. Rather than worry about what needs to be maintained, completely replace everything and start fresh with a basically maintenance-free roof.

Guaranteed warranties

Most contractors will guarantee their work for five to 10 years, but materials are usually covered for longer periods. However, by the time your roof is 20 years old, the manufacturer’s warranty, which is usually prorated, doesn’t offer much coverage. When you start new, so do your warranties with your contractor and manufacturer.

Increased property value

Curb appeal adds property value, which is important for homeowners who are looking to put their property on the market. But a new roof, which will add two-plus decades of protection to the home, can also bump up the resale value by between $12,000 to $15,000, depending on the size of the home and the type of materials used.

Roofing materials differ

You can’t put asphalt shingles on top of terracotta tiles – it just doesn’t work. The only way an overlayment works is if you’re using asphalt shingles on top of asphalt shingles. Mixing materials, whether it’s slate or wood, is not recommended.

The roof already has two layers

Building codes in Illinois do not allow more than two layers on roofs. If your house already has two layers, adding another layer simply is not an option. Most homes are not engineered to withstand such weight, which is why a three-layered roof is not legal.

Current shingles are curling or in bad shape

Installing new shingles on old shingles will only work if the old ones are in decent shape. This means they can’t be curling, which is fairly common with old and weathered shingles. If you’re set on preserving the old roof, your contractor will first have to replace trouble spots where curling is visible.

Keep in mind that what’s going on with your old roof will show up on your new roof. For example, any bump or gap on the old roof will imprint on the new one. Furthermore, these imperfections make installation of the new shingles difficult, which can lead to mistakes that result in big problems later.

One way around these imperfections is to use high-quality, thick architectural shingles that can better hide these imperfections, but it’s a premium product and will add on to the cost of the project.

Your roof leaks when it rains

When leaks are spotted in your old roof, there are obvious problems that need to be addressed, and it’s not usually something that can happen without a complete roof replacement. Rarely will the installation of new shingles on old leaky ones fix the problem.

Your roof is soft and spongy feeling

During the inspection process, the contractor will walk across the roof feeling for problem areas. Should they find a soft spot or a “spongy” area, they will know that there is a problem with the sheathing, which will need to be replaced. The best approach is a complete roof replacement.

Less visual appeal

The perk of getting a new roof is that you get that new roof curb appeal. But when you install a new roof over an existing one, you don’t usually get that perk. Rather, the roof might look uneven in areas and lack the consistency of a new roof. Furthermore, shingles are more prone to blow off in these situations, which is why establishing a firm base with new materials is preferred.

Shingles add additional weight

A roof on a 2,000-square-foot home usually spans around 3,000 square feet of surface area. And with the average asphalt roof averaging 425 pounds per 100 square feet, that’s a lot of weight. Now consider having two layers bearing all that weight on the structure. You quickly see how a load like that can put undue stress on a home. Add a snowstorm that dumps a foot or more of snow on your roof and the integrity of the structure is now further compromised.

Most homes in the Chicago area are designed to handle the load of one layer of shingles, as well as the weight of the typical amount of snow for the region. Adding another layer on that is deemed risky by most contractors because it can lead to sagging sheathing and eventually, leaks.

Shorter lifespan of the roof

A variety of existing issues can be detrimental to the lifespan of your new roof when it goes on top of one that is already compromised. For example, if there is any mold or algae growth, it will continue to get worse under the new shingles. Also, did you know a roof with two layers traps more heat than a roof with a single layer of shingles? Finally, even without existing issues, the average overlay roof only lasts for around 16 years.

Can't replace underlayment

Tarpaper, often referred to as underlayment or felt paper, is the layer that goes directly over the top of the sheathing, which is the .75-in. plywood base layer that serves as the roof deck. At some point, water will get under shingles, which is why the underlayment is there – it stops the water from getting into the sheathing. As the roof ages, the underlayment loses its ability to stop moisture from coming through and will eventually fail. Underlayment doesn’t work on top of the old shingles, which means when you do an overlayment, you’re taking a gamble that the old underlayment is going to hold up.

Improper roof inspections

Even though roofing contractors are pros at spotting problems on roofs, they don’t have X-ray vision, so they’re not going to be able to see all the problems hiding under an existing roof. Tearing off the old shingles will give them a thorough look at the roof decking, allowing them a chance to make the small, inexpensive repairs that would otherwise be expensive problems later.

Trickier maintenance

Problem areas are often spotted during routine inspections, which means a quick and easy repair on a roof with one layer of shingles becomes a far more complex problem when the roof has two layers. For example, if the base layer in the attic reveals the beginning of rot, that moisture source could be coming from anywhere, as the water coming through the shingles is diverted multiple times before it finds its way into the base layer.

Higher costs

Tearing off a roof comes at a cost, which for some homeowners is too hefty a price. A tear off adds to the labor, which is the biggest expense, but there are also dumpster permits and dumpster rental fees that also add to the cost. The average tear off adds roughly 25 percent more to the total cost of the roof project.

Takes longer

When time is of the essence, the complete roof replacement is not an option. Tearing off roof shingles takes time, which will add to the overall timeline of the project. When homeowners encounter time restrictions, the overlay is the way to go.

Excessive waste

Roofing projects are a messy venture, but when you have to tear off all the shingles, underlayment, nails and flashing, that only adds to the mess that must be cleaned up. When given the option, some homeowners will factor in the waste removal in their decision to avoid the tear off.

Consideration of the long-term price

Smart investors plan for the long term rather than trying to achieve short-term gains. Roofs are an investment, too. When considering the short-term gains of installing a new roof over an old one, you get only the immediate advantage of saving money, which is offset by a larger investment in a complete replacement or expensive repairs later, at which point it becomes clear that less money would have been spent if the project would have included paying for the complete tear off from the beginning.

Possible warranties issues

Warranties are important to homeowners. That’s why so many roofing contractors only work with materials that offer a warranty and it’s why contractors offer a warranty on their workmanship. Should you choose to do a recovery project, the warranty on the new shingles could be voided, so it’s important to talk to your contractor about that. The reason warranties are voided in overlays is that shingles aren’t built to be laid atop of the rough granules of other shingles, because doing so will cause abrasions and potential moisture leakage.

Local codes might not allow roof recovery

Most states, including Illinois, do not allow more than two layers on a roof, which means if your roof already has two on it, your only option is to do a complete tear off. Also, check your local building codes to ensure that having more than one layer of roofing is even allowed, because municipalities might have their own take on this issue.

Roof overlay might not look good on an inspection report

Do you plan on putting your house on the market anytime soon? This matters, because before you can sell a home, it has to be inspected and that inspection report will reveal details about your roof. If it has two layers on it, that could be a game changer for the buyer – and not in a good way. The reason is that when it comes time for the new homeowner to take on a roofing project, they will be forced to pay for the complete removal of the existing two layers.

While it might be a stretch to say that roof-recovering projects are a thing of the past, the practice has certainly fallen out of favor with contractors and homeowners alike. Roofing best practices dictate that a roof tear off should precede any roof installation.