Everything You Need to Know About Roof Overlays

If you notice signs that you need a new roof, you may be worried about whether you can afford to replace it. But there is a budget-friendly alternative to installing a new roof—a roof overlay. Read on to learn everything you need to know about the process of overlaying a roof, how it compares to a complete roof replacement, and the circumstances in which overlaying shingles on an existing roof may be the right choice.

What Is a Roof Overlay?

An alternative to a tear-off roof replacement, roof overlay (sometimes called “roof recovery”) is the process of applying new shingles and waterproofing to an existing roof. Rather than removing the old shingles and ripping out the old flashing and sealing, roofers simply cover them with a new layer. Compared to full roof replacement costs, an overlay significantly reduces the costs of labor and materials disposal. 

There is a catch, though; it can only be done once. After you add one layer of overlay shingles, your roof likely cannot support another layer, and most building codes allow a maximum of two layers of organic or fiberglass shingles on roofs with a pitch up to 18.5 degrees. And if you have major underlying problems with the original roof, an overlay is unlikely to correct them. Shingles that are warped and sagging will still look warped and saggy with another layer on top. Somewhat paradoxically, the best candidate for a roof overlay is a roof that is already in relatively good condition. 

Not all roofers will perform overlays, either because they are wary of the merits or because they cannot be confident enough in the underlying structure to guarantee their work without the full inspection that happens during a tear-off replacement. So, if you are considering a roof overlay, speak to a range of local roofing contractors to find one who can do your job. Local building codes also tend to be quite specific about the circumstances under which an overlay is or is not allowed, so make sure to do thorough research on the requirements in your area.

How Does a Roof Overlay Compare to a Tear-Off?

Can you shingle over shingles? Comparing the two options leaves one clear conclusion: Always go with a tear-off roof replacement, if possible.

Most expert roofers do not recommend overlaying new shingles on top of existing roofing for structural and longevity reasons. Instead, they almost always recommend roof replacement, including a complete tear-off of old shingles, inspection and repair of the roof decking below, and installation of entirely new, high-quality roofing materials that are backed by labor and material warranties.

If you must consider an overlay, be sure your contractor does it right. They should do the best inspection they can of your current roof, looking for leaks and damage. They should also explain the risks to your roof and home, warranty changes or voids, and other downsides for your specific situation. If that inspection shows no concerns, and you are comfortable with the risks and downsides, they can move forward with the overlay.

Roof Overlay Benefits

Photo: taniche / iStock / Getty Images

Roof overlays offer a few unique advantages over a full, traditional tear-off roof replacement. 

Cost

The total cost of a full roof replacement ranges between $8,700 and $22,000. Most homeowners’ primary motivation in considering a roof overlay versus a tear-off is savings. In the short term, a roof overlay is significantly less expensive than the alternative. By opting for an overlay, you skip out on paying for the labor time involved in removing the old shingles and the fees required to dispose of them. All told, an overlay could save 20% to 40% on your roof replacement. 

Quick Installation

By opting for a roof overlay, you are essentially cutting the replacement job in half, sparing contractors the work of removing and disposing of the old shingles. In the same way it lowers costs, it cuts down on the length of the work, as well as some of the mess it creates. Your home will be under construction for significantly less time and you will not need to deal with dumpsters, piles of old shingles, and discarded old nails.

Less Disruption

Because it does not include tearing off your old roof, roof overlays are much faster and less disruptive than complete reroofing work. You will not face hours or days of scraping overhead or having roofers on your property. This can be especially tempting for people who work from home or are home most of the time, as well as businesses that want to limit the interruption of roofing work.

Roof Overlay Disadvantages

The affordability and short installation time offered by a roof overlay come with their own disadvantages. 

Long-Run Cost

While the immediate costs of a roof overlay are much lower than a tear-off replacement, you are essentially deferring (and adding to) the costs of the tear-off replacement that will eventually have to follow. It will take longer and increase labor costs to remove two layers of shingles, and it will cost twice as much in dumping fees. 

Added Weight

With two layers of shingles, a roof overlay doubles the amount of weight your roof must support. While most building codes will allow for the additional layer, you need to be confident that the walls and foundation of your home are not just structurally sound but in tiptop shape, capable of bearing the additional stress over many years. If your foundation would require the installation of additional supports to carry the increased roof weight, any savings from avoiding a full roof replacement will quickly vanish. 

No Roof Inspection

As part of the standard tear-off roof replacement process, roofers must perform a detailed inspection of the roof deck beneath the shingles to catch and correct any problems with the structure, as well as the flashing or sealing. With an overlay, the first layer of shingles stays in place, so if the deck is rotting, leaking, or has other structural issues, you will not catch it until there is an evident problem. It is for this reason that some roofing contractors refuse to perform overlays, since they are unable to inspect the underlying roof carefully enough to make the standard assurances of quality.  

Shorter Lifespan

The average lifespan of a roof with asphalt shingles falls between 20 and 30 years. In principle, the second layer of shingles added in a roof overlay should last the same amount of time, but in reality it rarely does. How long does a roof overlay last? Roofers say that homeowners should expect the average overlay to last 15 years. 

The main culprit in limiting the longevity of an overlay is heat. The sun beats down heavily on a roof, with the dark shingles absorbing much of its heat. When there are two layers of shingles, heat gets trapped between them, accelerating the aging process for the top layer and sometimes causing them to warp and curl. In many cases, using shingles for an overlay will also void the manufacturer’s warranty, since shingles are designed to lie flat. 

Curb Appeal

If you are considering a roof overlay, inevitably it is because you have some problems with your existing roofing. In many cases, adding a second layer of shingles will fail to hide, or can even exacerbate, the cosmetic problems that are already present. If the underlying shingles are curled or warped, the new ones will settle into the same shape. Even when the bottom layer is relatively even, it is a lot more difficult for a roofer to lay a smooth, neat layer on top of shingles when compared to wood decking. Because shingles are designed to be laid on a flat wooden surface, they may also be less stable in an overlay, catching and blowing off in high winds or heavy precipitation. 

Return on Investment (ROI)

Even an attractive, well-installed roof overlay can be a red flag to buyers, lowering the sale price of your home. The fact that you had the overlay performed can make buyers wary about the state of the underlying roof; and even if they can be assured that there are no major structural problems, they know they will be inheriting an additionally expensive roof replacement when the time comes. At the very least, a roof overlay will fail to increase the value of your home in the way that a full roof replacement would; in many cases, it can lower the value beneath the costs of the overlay, resulting in a negative ROI. 

Maintenance Complications 

With an overlay in place, standard roof maintenance work can become trickier. If, for example, your roof starts leaking, it is a lot more difficult to identify the source and get at it to repair, since there is an additional layer of shingles to work with.

Can You Overlay a Metal Roof?

Perhaps surprisingly, if you insist on a roof overlay, your best option might be to place a metal roof on top of your old shingle roof. Here is why:

• Metal roofing systems are lightweight, with most weighing less than a pound per square foot, so they do not add as much of a load to your existing roof system as a second layer of shingles.

• Metal roofs often require or benefit from an added layer of insulation between the metal sheets and the roof decking to help block temperature changes to the attic and provide sound insulation. An old shingle roof can provide this insulating value.

• Since metal roofs are usually much more durable and do a better job of preventing leaks than shingles, the risk of leaks through the underlying roof is reduced compared to shingle-on-shingle overlays.

• If you choose a standing seam metal roof as the overlay, you will not need to worry about stray screws or shingle nails piercing the underlying shingles and creating new leaks. Unfortunately, however, the reverse is true: Adding a screw-down metal roof on top of an old asphalt shingle roof can be a recipe for future leak disasters.

Similarly, you can overlay a new metal roof on top of an aging metal roof. Like with overlaying asphalt shingles, this process is not recommended as much as replacing the old roof with a new one, but it can be a decent solution in some situations. It can save labor, time, money, and disruption. But it comes with challenges and downsides, too, and you should always discuss these with your roofing contractor before making a decision.

Some roofers will overlay old metal roofs with TPO (thermoplastic polyolefin) or PVC (polyvinyl chloride) membrane, both of which are a single-ply white membrane roofing material used most commonly on flat roofs. This is an uncommon overlay approach that is not often used on residential buildings, but it can be a solution for commercial and industrial buildings. Like with metal-on-metal overlays, you will need to discuss the specific pros and cons of this option with your roofer to discover whether it makes sense for you.

When to Choose a Roof Overlay

For many homeowners, the downsides of a roof overlay outweigh the cost savings and the shorter installation time, but there are some situations in which it may be the best option. 

If you are dealing with an urgent problem, like a roof leak, during a time when money is tight, a roof overlay can be a lifesaver, providing a significantly more affordable means of getting the issue under control and preventing further damage. You know that you will be paying more down the line when it eventually comes time to opt for a tear-off replacement and that you are essentially borrowing money from the future, with those additional costs functioning like interest on a loan. 

A roof overlay can also be a good choice if you are looking to sell quickly and want to affordably remedy some minor cosmetic problems with your existing roof. In some cases, a recent overlay will make buyers somewhat wary, but you can dispel their fears if you properly document that the underlying roof is in relatively good shape and that the overlay was performed correctly, demonstrating that the buyers will get at least 10 to 15 years out of the new shingles.

Finally, it may make sense to choose a roof overlay over a full replacement if your roof system is in good shape beyond some cosmetic issues with the shingles and if you put the money you save on labor toward higher-quality materials than you would use otherwise.

When Not to Choose a Roof Overlay

As we have seen, there are a lot of reasons to go with tear-off reroofing rather than a roof overlay. Here are the top reasons not to choose a roof overlay. 

If Your Home Is Older

Older homes can have wider or weaker roof rafters and roof trusses, weaker roof beams, and weaker framing support systems than more modern homes. Building codes and best practices have changed, and different types of roofing materials have gotten heavier. So, if you add what is essentially a second roof on top of your home, you may end up compromising your home’s safety. Instead, go with a full reroof that includes tearing off the old roofing materials to lighten the load your home has to carry.

If Your Home Is Structurally Unsound

If your home has structural problems or needs foundation repairs, you definitely want to skip the temptation to install a double-decker roof. This will add too much weight to your home’s structural support system and foundation, and it can cause major issues over time, including further damage and roof collapse. In fact, if you are worried about your home’s stability or have questions about the structure itself, it is best to contact a structural engineer before doing any work to your home, including new roofing.

If Your Roof Has Dips or Sags

You may not notice it from inside, but if your roof has visible dips, sags, or other warning signs, you should not attempt a roof overlay. Instead, hire a roofer to perform an inspection to determine what the problem is. It could be a problem with your roof deck, roof supports, or even a foundation issue. If it is simply lack of support, you should include roof truss costs in your roof replacement budget, but you are still likely to save money (and your home’s integrity) by putting on a new roof altogether.

If Your Roof Deck Is Damaged

Roof sheathing, also known as decking, is the layer of flat boards on top of your attic’s rafters and beneath the shingles. It is just one of the many parts of a roof that can sustain damage or grow weak over time. Roof deck damage may include leaks, dry rot, sagging, lack of support, and other issues. Because roof sheathing carries the load of the roof, you should never overlay new roofing on damaged decking. Talk with your roofing contractor about your options, but your best move is probably a full roof replacement.

If Your Roof Leaks

While roof overlays can be an acceptable option in some cases, they are not the answer if your roof leaks. That is because, while overlays can temporarily stop the old roof from leaking, applying a new roof will not do anything to address damage under your current roof. That means mold, mildew, dry rot, and other issues will remain and continue to cause problems.

If You Want the Most Durable, Long-Lasting Roof

Roofing material lifespans vary, but you will almost always get a more durable and longer-lasting roof by tearing off the old materials before you put on your new roof. The simple truth is that, while roof overlays can be less expensive at first, they rarely hold up as long as entirely new roofs. For a roof that lasts a long time, it can be smarter to spend a little more upfront for a total roof replacement.

If You Want a Full Roofing Warranty

Roofing manufacturers usually back up their products with warranties, and qualified roofers who install them should guarantee their work in writing. But with shingle overlays, both product manufacturers and roofers may not be able to offer roof warranties. That is because overlays do not provide the optimal conditions for roof shingles, so makers and installers cannot always guarantee the long-term outcome.

If You Are Looking for the Highest Resale Value

Homeowners researching the best home improvements for resale value often find that new roofs command a big ROI. But those statistics are for new roofs and total roof replacements, not roof overlays. In fact, roof overlays can scare off buyers because they may not trust what is underneath or be afraid of the added cost of eventually removing both the overlay and the old roof underneath it. If you want the highest resale value for your home and need a new roof, talk with your roofer about the best options.

There are so many possibilities for roof replacements and situations vary so greatly that it is best to discuss them with a qualified roofer near you. A professional can look at your current roof, give you tailored advice for new roofing, and help you find the right solution, whether it is a roof overlay or a roof replacement.