You've seen them. The driveways with spiderweb cracks after one winter. The foundation walls with separation gaps by year two. The garage floors that look 20 years old after 24 months. Here's what's happening: Contractors bring "flatland techniques" to 6,500+ feet elevation. They don't account for extreme temperature swings. They ignore bedrock composition. They use mix designs created for sea-level construction. And they wonder why their work fails. In Durango and Pagosa Springs, concrete doesn't just sit on soil.