The good news is that if you're looking for an affordable product to fix hairline cracks in concrete retaining walls, elastomeric paint is a far better solution than standard exterior paint. Originally introduced in the 1950s, elastomeric paint was first used as a roof coating. The long molecule chains in this coating allow it to expand and contract, making it perfect for bridging the hairline cracks in retaining walls and other masonry surfaces. Retaining walls are one of the top uses for elastomeric paint, since they're subject to forces like hydrostatic pressure and moisture on one side and wind and weather on the other. Behr's 1-gallon Elastomeric Masonry, Stucco and Brick Exterior Paint can withstand up to 98 mph wind-driven rain, lasting about 10 to 15 years when applied correctly.