The answer to 'why is my shingles sagging' is that shingle sagging is often caused by improper installation, old age, or moisture damage. Shingles can sag due to nails that were not properly secured, insufficient roof ventilation, or rotting of the roof deck underneath. Sagging shingles are more than just an aesthetic issue - they can lead to leaks and further damage if not addressed.
If you notice your shingles starting to sag, it's important to have a professional roofing technician inspect your roof as soon as possible. They can identify the root cause and recommend the best solution, whether that's re-securing the shingles, replacing damaged areas of the roof, or a full roof replacement.