The answer to 'shingle replacement sagging' is that shingle sagging is usually caused by inadequate roof support, improper installation, or aging roofing materials. Symptoms include visible dips or depressions in the roof line, cracks or splits in the shingles, and water leaks. Solutions may involve reinforcing the roof structure, replacing damaged shingles, or a full roof replacement.
In many cases, shingle sagging is a complex issue that requires the expertise of a professional roofing contractor. DIY repairs are generally not recommended, as improper work can lead to further damage and safety hazards. Homeowners should consider calling a local roofing expert to inspect the roof and provide the best course of action.