In general, it is not recommended to install new wood shake roofing material directly over old asphalt tiles without removing the old covering first. While it may seem like a convenient option, there are several reasons why it's best to tear off the old tiles before installing the wood shakes:
Weight: Adding another layer of roofing material increases the weight on the roof structure. If the structure was designed and built to support a single layer of roofing, adding an extra layer may exceed the weight limits and potentially compromise the structural integrity of the roof.
Uneven surface: The existing asphalt tiles may have warped or uneven areas, which can create an uneven surface for the wood shakes. This can lead to poor installation, compromising the overall performance and lifespan of the new roofing material.
Moisture issues: Moisture trapped between the layers can lead to various problems, including rot, mold, and deterioration of both the old and new materials. Removing the old tiles allows for proper inspection and repair of any underlying issues, ensuring a sound roofing system.
Warranty concerns: Many manufacturers of wood shake roofing materials require the old roofing material to be removed before installation to honor their warranty. Failing to adhere to these requirements may void the warranty, leaving you responsible for any potential issues that may arise.
It's always advisable to consult with a professional roofing contractor who can assess your specific situation and provide the best recommendations for your project. They will consider factors such as the condition of the existing roof, local building codes, and manufacturer guidelines to ensure a safe and durable roofing installation.