Five primary causes: subcontractor availability gaps (scheduled trade is committed elsewhere — the most common cause in residential construction); material delivery delays for long-lead items not identified as critical path items; permit processing delays not accurately built into the pre-construction schedule; scope creep through undocumented change orders that extend phase durations without schedule adjustments; and weather delays not buffered into the schedule. RainFire Builders addresses the first cause structurally by self-performing all ten interior trades. Long-lead items are identified at the estimate stage. Permit timelines are municipality-specific. Change orders document schedule impact. Weather buffer is built into weather-sensitive phases at schedule development.