Laying Shingles Over Existing Ones

When laying shingles over existing ones, there are several potential problems that can arise:

• Excessive Weight: Each layer of shingles adds extra weight to your roof. If your roof structure is not designed to support the additional weight, it can lead to structural damage and compromise the integrity of your roof.
• Reduced Lifespan: The new layer of shingles is not able to properly bond with the roof deck when installed over existing ones. This can result in premature wear and tear, reducing the lifespan of the shingles and can potentially cause leaks.
• Decreased Energy Efficiency: Layering shingles can create an additional barrier that prevents proper ventilation in your attic. This can lead to increased heat buildup, reduced energy efficiency, and potential moisture issues.
• Concealed Damage: Installing new shingles over existing ones can make it more challenging to identify and address underlying issues – such as damaged decking or flashing. It’s important to address these issues before installing a new roof to ensure the long-term integrity of your roofing system.
• Warranty Voidance: Manufacturers’ warranties may become void if shingles are installed over existing ones. It’s important to review the warranty guidelines and consult with a professional roofer to ensure compliance.
• Aesthetics and Resale Value: Layering shingles can result in an uneven appearance, particularly if the existing shingles are not in good condition. This can negatively impact the curb appeal of your home and potentially affect its resale value.

It's important to note that while some jurisdictions allow for shingle layering, it’s generally not recommended due to the potential problems mentioned above. It’s always best to consult with a professional roofing contractor to assess your roof’s condition and determine the most suitable approach for your specific situation.