The answer to 'why is my skylight sagging' is that a sagging skylight is often caused by structural issues or improper installation. Common causes include inadequate support, water damage, or settling of the roof over time. Symptoms may include cracks, leaks, or the skylight frame appearing uneven or distorted.
If your skylight is sagging, it's best to have a professional roofing technician inspect it. They can diagnose the underlying issue and recommend the appropriate repair, which may involve reinforcing the frame, replacing damaged components, or even re-installing the skylight entirely. Attempting DIY repairs on a sagging skylight could be unsafe and may lead to further damage, so it's generally advisable to call in an expert.