San Antonio sits on expansive clay soil that swells when wet and contracts during drought. This movement shifts foundations and stresses roof framing over time. When you add a second layer of shingles, you increase the dead load on trusses that may already be under stress from soil movement. The trapped heat between the two shingle layers accelerates adhesive breakdown and granule loss. Your new shingles age faster in San Antonio than they would in cooler, more stable climates. The cost savings you gain upfront disappear when you have to replace the roof in 12 years instead of 20.
Summit Roofing San Antonio works with structural engineers when we evaluate overlay projects on homes built before 1980. Older truss designs were not engineered for the added weight of a second shingle layer, especially when combined with modern impact-resistant shingles that weigh more than standard three-tab products. We also understand the permit requirements in different San Antonio jurisdictions. The city requires engineered drawings for some overlay projects depending on roof pitch and square footage. We handle that paperwork so your project stays compliant and your insurance stays valid.
