The answer to 'difference between shingle replacement' is that shingle replacement involves completely removing and replacing all the shingles on your roof, while spot repair is fixing or replacing only the damaged or worn shingles. Shingle replacement is a more comprehensive solution that addresses the entire roof, while spot repair is a more targeted fix for specific problem areas.
Shingle replacement is typically recommended when the roof is nearing the end of its lifespan (around 15-20 years for most asphalt shingles) or if there is widespread damage across the roof. This ensures the entire roof is updated and protected from the elements. Spot repair, on the other hand, is a good option if only a few shingles are damaged or missing. It's a more cost-effective solution, but may not address underlying issues that could lead to further problems down the line.