The answer to 'why is my roof decking worn out' is that the roof decking, which is the structural foundation for the roofing materials, can become worn out over time due to a variety of factors. Common causes include exposure to the elements, water damage, and structural issues with the home. Symptoms of worn-out roof decking can include sagging, soft spots, or visible damage to the plywood or OSB panels.
In many cases, worn-out roof decking will need to be repaired or replaced by a professional roofing contractor. This is not typically a DIY project, as it requires specialized knowledge and tools to properly assess the extent of the damage and make the necessary repairs. Attempting to repair or replace roof decking without the proper expertise can lead to further damage or safety issues.