Replacing your roof is a major project. If your roof is beyond repair or past its useful lifespan, it’s time to make plans to replace it. If this is the case, you have two options: overlay new shingles onto the existing roof or tear off the old first, then add new shingles. When dealing with a roofing contractor, be sure to understand the pros and cons of shingle overlay vs. tear off options.
Shingle Overlay
If your roof’s shingles are in good condition, placing another layer of shingles down over them is an option. It eliminates the messy and labor intensive removal process called the “tear-off.” This can save you money for the roof project.
Although it may seem like having multiple layers of shingles would be beneficial, it does not necessarily make your roof more waterproof or energy-efficient. More often, it ends up creating problems for you in the future.
We don’t recommend putting new shingles over the old roof if there’s a lot of:
- Warped shingles
- Mildew, moss, or fungal infestation
- Significant structural damage
However, if your roof is in good condition with a bit of wear, you can save some time and money by putting another layer over them. There is a catch however: International Residential Code.
R908 of the International Residential Code is the standard for building all US buildings. It covers new roof coverings on top of existing layers of roofing. The code restricts you to a maximum of two roof coverings (shingles). So if you’ve already roofed over once, you can’t do it again.
Plus in some areas, there may be local codes that restrict you to one. For instance, towns located in climates that have a heavy hailstorm or significant ice dam issues may not allow for multiple roofing layers.
Complete Roof Replacement
While shingle overlay has the distinct benefit of being the quicker and cheaper roof replacement option, we will usually recommend that you tear off and replace the entire roof to ensure your roofing system works as it should.
Here are a few reasons why you should replace your roofing system, rather than covering it up:
Eliminate Mold & Decay
One of the biggest reasons to replace, not cover up your existing roof is because of the mold and decay that could be present on or around your present roofing system. During a full roof replacement, all of the old roofing system is torn off, disposed of and then replaced with a completely new roof.
If you install a new roof over your old, you not only run the risk of keeping any existing mold and decay around, but also of further promoting its growth. If there is moisture present on or under your old roof, covering it with a new layer essentially traps the moisture. This can aid the growth of any mold and cause your roof to decay even faster, leading to expensive repairs.
Ensure the Roof is Flat
If you overlay new shingles over those that are there, the new shingles may not lay flat over gaps, dips or humps from the existing roof. Although skilled roofers know how to lay new roof shingles over existing ones, it could be tricky.
If any old shingles are cupped, curled or in bad shape, then those defects will show in the new layer as well. For this reason, several roofing experts recommend using laminated or dimensional shingles for reroofing projects. This is because these tend to be thicker than standard shingles. They also have a staggered edge profile, which helps in hiding any dips or high spots in the old roofing.
If you plan to overlay new shingles over the existing roof, you can only do it if the current roof is asphalt and you are adding another asphalt shingle layer. You can not lay down asphalt shingles over cedar shakes.
Adds More Weight onto Your Roof
Good-quality shingles can weigh up to 350 to 450 pounds per square. Chances are, the roof structure of your property was designed to bear a dead load of one layer of shingles along with extra strength to bear snow and a safety margin.
Installing new roof shingles over the old one effectively doubles the weight of the roofing. You have to ensure your roof’s structure is capable of handling this extra load. As stated above, the International Residential Code does not allow more than two layers of shingles.
On certain properties, the extra weight from multiple layers causes the roof sheathing to sag in between the rafters or trusses. Small roofs don’t have the capacity to handle immense amounts of weight. A second layer on your roof only increases that strain and can result in further roof problems. This is especially prominent if the area you’re living in receives a great amount of snow each year.
Even for medium-sized homes, the addition of additional shingle weight can cause a number of issues once winter arrives.
Unable to Inspect Roof Sheathing and Underlayment
Your roof deck, roof felt and tarpaper underlayment support all the shingles and flashing above. Damage on their part can lead to a roof disaster. Without a tear off of the old shingles, roofers are unable to see what the decking looks like.
By peeling back to the deck, your roofers now can check on its state. Wood rot and damage or poor installation of the felt nails or screws can spell big costs down the line. If the shingle underlayment is old and deteriorated, it won’t be able to protect your roofing deck from water that gets past the shingles.
In snowy climates, new roofs will install an ice-and-water shield. This is a rubbery moisture membrane that is applied to the sheathing along the eaves to serve as a protection against ice dams. Adding this layer of membrane isn’t an option that is present with a shingle overlay. The extra layer of shingles offers little protection against ice dams. In the long run, a tear off can save money.
Increase the Life and Quality Of Your Roof
Naturally, allowing your roofing contractor to properly install your roof can lead to a longer lifespan for your new roof. Roofs that have been completely replaced:
- Lay more evenly on the decking of your home
- Are subject to less moisture issues
- Just look better than roofs that have been layered on top of each other.
In addition, check with the shingle manufacturer about their warranty. There may be restrictions on choosing a shingle overlay rather than a complete roof replacement.
May Be More Costly Over Time
Pay me now or pay me later rings true when it comes to your roof. You need weight the long-term costs and potential risks associated with shingle overlay. Opting for a shingle overlay can end up being more costly than a replacement project. The idea of saving a thousand dollars from a simple reroofing plan may sound appealing. But not addressing the hidden issues that lay hidden under your current shingles may lead to a more expensive future project. Removing old shingles and replacing them with a complete roofing system with a warranty will save you more money in the long run.
Can Undermine Selling Your Home
Adding new roof shingles over the old ones may seem tempting to a lot of people who plan to sell their properties in the near future. Why should you pay for a tear off if you can just overlay new shingles?
However, those looking to purchase your property may not want to deal with the roofing project. Home inspectors will report double-layer roofs if they find them on your property. This serves as a warning to buyers of potential problems that could arise.
Which is Right for You?
When it comes to deciding between shingle overlay vs tear off, most roofing companies do not recommend layering a new roof on top of the existing roof material. While roof overlay is a short-term, economical solution, it may not be the best option for your home or your family.
We recommend that a roof replacement is your beset option because we have a chance to examine the roof structure and make repairs if any are needed. When you overlay, you are trusting that there are no issues lurking underneath the shingles.
Want to know which option is right for your roof or if your roof can be repaired instead of replaced? Contact Remodart and our professionals can provide a free estimate and help you decide.
