To repair a broken exterior wall expansion joint, first clean the joint using a wire brush and high-pressure water to remove debris and old sealant. Apply a backer rod of the appropriate diameter to fill gaps larger than 1/4 inch. Then, use a polyurethane or silicone sealant specifically designed for exterior use, cutting the tube nozzle to match the joint width. Press the sealant into the joint with a caulk gun, ensuring full coverage and uniform depth. Finally, smooth the surface with a damp rag and allow the sealant to cure fully according to the manufacturer’s instructions, typically 24–48 hours. Regularly inspect and maintain the joint every 1–2 years to prevent recurrence.

Expansion joints are critical for accommodating thermal expansion and material movement, which can cause structural stress if unaddressed. According to the American Society of Civil Engineers (ASCE), 30% of building failures linked to exterior walls involve improperly maintained expansion joints. Unsealed joints allow water infiltration, which accelerates material degradation. A 2021 study by the National Institute of Building Sciences found that water damage from unsealed joints costs U.S. property owners over $12 billion annually. Additionally, the U.S. Department of Energy notes that proper joint maintenance reduces energy loss by 15–20%, as moisture and air leaks increase heating and cooling demands. Using high-quality sealants like polyurethane, which resist UV degradation and maintain elasticity, extends repair longevity by up to 10 years compared to cheaper alternatives. Neglecting repairs can lead to costly structural repairs, such as foundation cracks or interior mold, which average $5,000–$10,000 to resolve. Thus, proactive maintenance protects both structural integrity and financial investments.