A flush threshold requires careful engineering because Las Vegas gets driving sideways rain at 40 to 60 miles per hour in hillside communities, making even a three-foot overhang insufficient on its own. Without a proper overhang and threshold lip, water will intrude. The most reliable approach is pairing large slider doors with a fully covered patio. Newer drainage systems can achieve the flush look without the traditional four-inch step-down, but they require more planning and integration during design.