How to Decide if You Should Install New Shingles Over an Old Roof
When the time comes to replace the roof of your home, one of the first decisions you must make is whether to install new shingles directly over the old roof or to remove the existing shingles before installing the new ones. This choice can be tricky, as there are several factors to consider, including the cost, the condition of the old roof, the type of materials involved, and the long-term durability of the finished roof. While installing shingles over an old roof may seem like a cost-effective and time-saving solution, it can come with several drawbacks. In this essay, we will examine the pros and cons of installing new shingles over an old roof and why it is often better to remove the old roof before installing a new one.
Pros of Installing New Shingles Over an Old Roof
Ridge vents are installed along the peak or ridge of the roof. They are one of the most effective and aesthetically pleasing forms of exhaust ventilation. Ridge vents work by allowing hot air to escape from the attic naturally, without the need for additional powered ventilation. These vents are often paired with soffit vents, which serve as the intake vents. Together, they provide continuous, passive airflow. Ridge vents are popular because they are discreet and do not disrupt the roofline or appearance of the home.
2. Soffit Vents
Soffit vents are installed along the eaves or soffits of the roof, typically under the overhang. These are intake vents that allow cooler, outside air to enter the attic. They work in tandem with ridge vents to create an effective ventilation system by facilitating a natural flow of air into the attic. Soffit vents are usually made of perforated metal or vinyl and are often placed in continuous strips to maximize airflow.
3. Gable Vents
### The Basics: Shingles Over an Old Roof
Before diving into the pros and cons, it’s important to understand what it means to install new shingles over an old roof. This process, known as a “reroof” or “roof overlay,” involves adding a new layer of shingles on top of the existing roof materials. The underlying assumption is that the old roof is still in decent condition and can provide a stable base for the new shingles. Reroofing is a relatively quick and less expensive way to replace a roof, but it’s not without potential issues.
### Pros of Installing New Shingles Over an Old Roof
#### 1. **Lower Initial Costs**
One of the biggest advantages of installing shingles over an existing roof is cost savings. Removing the old roof requires time, labor, and disposal fees, all of which can add up. When shingles are simply layered over the old roof, you avoid the costs associated with tear-off and disposal, leading to a lower overall cost for the project. This can be especially appealing for homeowners on a tight budget or those who are looking for a temporary solution to prolong the lifespan of their roof.
#### 2. **Faster Installation**
Reroofing is typically a faster process compared to a full roof replacement. The old shingles don’t need to be removed, which means workers can spend more time installing the new shingles. In many cases, reroofing can be completed in just one or two days, whereas a complete tear-off may take longer due to the need for disposal and the additional labor involved. For homeowners who need their roof replaced quickly, reroofing may seem like an attractive option.
#### 3. **Less Disruption**
A reroofing project can be less disruptive than a full roof replacement. During a tear-off, there can be a significant amount of noise, debris, and dust. The process of removing old shingles may also expose the roof deck to the elements, increasing the risk of water damage if the project is delayed. By installing new shingles over the old roof, the work is generally quieter and less invasive, with minimal exposure to the underlying structure.
#### 4. **No Need for Disposal**
Removing old shingles involves a significant amount of waste, which must be carefully managed and disposed of, often at an additional cost. Installing shingles over the old ones eliminates the need for hauling away the old roofing materials, reducing both labor and environmental costs.
### Cons of Installing New Shingles Over an Old Roof
#### 1. **Potential for Hidden Problems**
One of the primary downsides to installing new shingles over an old roof is that you may be masking underlying issues. For example, if the existing roof has problems such as water damage, mold, rotting, or structural issues, these will remain concealed beneath the new shingles. While new shingles may temporarily cover up these issues, they won’t address the root cause. Over time, hidden problems could worsen and lead to costly repairs down the road, often when it’s too late to remedy the damage.
#### 2. **Reduced Lifespan of the New Roof**
While reroofing might save money in the short term, it can reduce the overall lifespan of your new roof. A typical asphalt shingle roof lasts between 20 and 30 years when installed properly. However, a second layer of shingles can cause added weight and stress on the underlying roof structure, especially if the roof deck is already weakened by the old shingles. This added weight could potentially shorten the life of the new shingles and cause premature wear. Additionally, because the roof’s ventilation may be compromised by adding another layer, heat and moisture could become trapped, causing the new shingles to degrade faster.
#### 3. **Increased Roof Weight**
The added weight of a second layer of shingles can put extra stress on the underlying structure of the roof. If your home has an older or weaker roof deck, adding another layer of shingles could exacerbate the problem, potentially leading to sagging or even structural failure in extreme cases. This is particularly important to consider if your home is in a region with heavy snow or frequent storms, where the roof may be subject to additional stress from precipitation.
#### 4. **Decreased Home Value**
A reroofed home may not command as high a resale value as a home with a completely new roof. Potential buyers may be wary of the fact that the roof has been layered, as it could signal that the previous homeowner was trying to cut costs or avoid a necessary repair. In some cases, buyers may be concerned about the hidden problems that could exist beneath the surface layer, even if the roof appears fine on the outside. This could affect the home’s marketability, especially in a competitive real estate market.
#### 5. **Warranty and Insurance Issues**
Some roofing manufacturers and insurance companies may have specific guidelines that prohibit reroofing. A manufacturer’s warranty for new shingles may not cover damage if the new shingles are installed over an old roof, leaving the homeowner responsible for any repairs. Additionally, certain insurance policies may not cover damages caused by improperly installed roofs, which could be a concern if the reroofing was not done according to industry standards.
### Why It Is Better to Remove the Old Roof
Despite the apparent advantages of reroofing, there are several compelling reasons why it is generally better to remove the old roof before installing a new one.
#### 1. **Addressing Structural Issues**
When you remove the old shingles, you have the opportunity to inspect the roof deck for any signs of damage, rot, mold, or other issues that could compromise the integrity of the roof. If the roof deck is compromised, replacing the old roof entirely allows for repairs to be made before new shingles are installed. This proactive approach ensures that your new roof will be as durable and reliable as possible, reducing the risk of problems later on.
#### 2. **Improved Ventilation**
Proper ventilation is critical to the longevity of a roof. Adding a second layer of shingles can impede airflow, leading to trapped heat and moisture beneath the surface. This can cause shingles to degrade more quickly, increase the likelihood of mold or mildew growth, and potentially damage the roof deck. When you remove the old shingles, you can inspect and improve the ventilation system, ensuring the new roof is well-ventilated and protected from these issues.
#### 3. **Long-Term Cost Savings**
While removing the old roof requires a larger initial investment, it often leads to better long-term savings. Without the underlying issues, the new roof will last longer and perform more effectively. Furthermore, addressing ventilation and structural problems early on can prevent more costly repairs in the future. Ultimately, replacing the old roof is a more reliable investment in the durability and longevity of your home.
#### 4. **Compliance with Building Codes**
In many areas, local building codes have specific regulations regarding how many layers of shingles can be installed on a roof. In some regions, reroofing may be limited to just two layers, and beyond that, homeowners must remove the old shingles. If you choose to reroof instead of removing the old shingles, you risk violating local codes, which could lead to fines or difficulty selling your home in the future.
### Conclusion
Deciding whether to install new shingles over an old roof or to remove the existing roof before installing a new one depends on various factors, including cost, the condition of the current roof, and long-term goals for your home. While reroofing offers several immediate benefits, such as lower costs and faster installation, it also comes with significant risks, including hidden damage, reduced roof lifespan, and potential structural problems. In many cases, removing the old roof is the better choice. It allows you to address underlying issues, ensure proper ventilation, and ensure a longer-lasting, more reliable roof. While it may be more expensive upfront, the long-term benefits of removing the old roof far outweigh the convenience of reroofing, making it a safer and more durable investment for your home.