Why You Shouldn’t Install New Asphalt Shingles Over Old Ones: A Comprehensive Guide

When it comes to roofing, homeowners often look for ways to save time and money. One common approach is to install new asphalt shingles directly over the old ones. While this might seem like a practical and cost-effective solution, it can lead to a host of problems down the road. In this blog post, we’ll explore why it’s important to avoid this shortcut and why removing the old shingles is the best course of action.

1. Excess Weight on Your Roof Structure

One of the most significant concerns with layering new shingles over old ones is the added weight. Asphalt shingles are already heavy, and doubling up on them can put unnecessary strain on your roof structure. Most roofs are designed to support only one layer of shingles. Adding a second layer could lead to structural issues, including sagging or, in extreme cases, even collapse. This is particularly risky in areas prone to heavy snowfall, where the weight of the snow combined with multiple layers of shingles could pose a serious danger.

2. Compromised Installation Quality

When new shingles are installed over old ones, they may not lay flat, creating an uneven surface. This unevenness can lead to several issues:

• Gaps and Poor Sealing: Shingles need to be properly aligned and sealed to protect your home from water infiltration. An uneven surface can cause gaps, making it easier for wind and water to penetrate the roof.
• Increased Risk of Wind Damage: If shingles are not securely fastened due to the uneven surface, they are more likely to be lifted or torn off during high winds, leading to further damage.

In short, the quality of the installation is compromised when new shingles are placed over old ones, leading to a roof that is less effective in protecting your home.

3. Reduced Lifespan of Your New Roof

Shingles are designed to work optimally when installed on a flat, clean surface. When laid over old shingles, the new ones may not perform as intended, which can shorten their lifespan. The irregularities of the old shingles can cause the new ones to wear unevenly, leading to premature aging and the need for a roof replacement sooner than expected. Essentially, by trying to save money on the installation, you may end up spending more in the long run.

4. Hidden Problems Beneath the Surface

One of the most critical reasons to avoid layering shingles is the potential for hidden issues. Old shingles can mask underlying problems such as:

• Rotting Wood: The deck or sheathing beneath the shingles can begin to rot if it has been exposed to moisture. This rot weakens the roof structure and can spread if not addressed.
• Leaks: Existing leaks may not be visible when new shingles are placed over old ones. Over time, these leaks can cause significant damage to the interior of your home.
• Mold Growth: Moisture trapped between the layers of shingles can lead to mold growth, which poses health risks to your family and can be costly to remediate.

By removing the old shingles, you have the opportunity to inspect and repair any underlying issues, ensuring your new roof is built on a solid foundation.

5. Warranty Concerns

Most shingle manufacturers provide warranties that are contingent on proper installation. Installing new shingles over old ones can void the warranty, as it is often required that shingles be installed on a clean, flat surface. If you encounter issues with your roof later on, you may find that your warranty is invalid, leaving you responsible for the full cost of repairs.

6. Aesthetic and Curb Appeal Issues

Finally, the appearance of your roof matters. Layering shingles can create an uneven, bumpy surface that detracts from the overall look of your home. This can negatively impact your home’s curb appeal and, in turn, its resale value. A clean, single layer of shingles not only performs better but also looks better, contributing to a more attractive home.

Conclusion

While it might be tempting to save time and money by installing new asphalt shingles over old ones, the risks far outweigh the benefits. From potential structural damage to a compromised installation and reduced roof lifespan, the drawbacks are significant. By removing the old shingles and starting fresh, you ensure that your roof is properly installed, fully functional, and covered by a warranty. In the long run, this approach will save you money, protect your home, and provide peace of mind knowing that your roof is built to last.

If you’re considering a roof replacement, it’s always best to consult with a professional roofing contractor who can guide you through the process and ensure that your new roof is installed correctly. Remember, a well-installed roof is an investment in the longevity and safety of your home.