Installing metal roofing over shingles is generally not a good idea for several reasons:
- Extra Weight: Adding a layer of metal roofing on top of existing shingles adds significant weight to the roof structure. Most roofs are designed to support the weight of just one layer of roofing material. Adding another layer, especially a heavier material like metal, can exceed the roof’s load-bearing capacity, potentially leading to structural issues and even collapse.
- Trapped Moisture: Shingles can trap moisture between the two layers of roofing materials. This trapped moisture can lead to rot, mold, and deterioration of the underlying shingles and roof deck. Over time, this moisture can cause damage to the roof and compromise its integrity.
- Uneven Surface: Shingles can have an uneven surface due to wear and tear, making it challenging for the metal roofing to lie flat and be properly secured. This can create gaps and vulnerabilities where water can infiltrate and cause leaks.
- Voided Warranties: Manufacturers of metal roofing systems often require installation on a clean, smooth surface to honor their warranties. Installing metal roofing over shingles may void the warranty, leaving you unprotected in case of any issues with the roofing system.
- Poor Aesthetics: Installing metal roofing over shingles may result in an unattractive appearance due to the unevenness of the shingle layer underneath. This can decrease the curb appeal and value of your property.
- Code Compliance: Building codes and regulations may prohibit installing metal roofing over shingles. It’s essential to comply with local building codes to ensure the safety and legality of your roofing project.
Instead of installing metal roofing over shingles, it’s best to remove the existing shingles before installing the metal roofing. Removing the shingles allows for proper preparation of the roof deck, identification and repair of any underlying issues, and a clean surface for the metal roofing to be installed correctly and effectively. If you are considering metal roofing, it’s advisable to consult a professional roofing contractor who can assess your specific situation and provide appropriate recommendations for your roofing needs.
