Overlap Method

Overlapping is the fundamental principle by which all non-membrane roofing systems achieve their weatherproofing. Whether using tiles, corrugated sheets, or standing-seam panels, each element is positioned so that its lower edge overlaps the upper edge of the element below, and its side edge overlaps the adjacent element. This creates a series of channels that direct water downward and outward, preventing it from being driven back under the covering by wind or capillary action. For metal roofing, the end lap (vertical overlap between sheet lengths) is typically 150-200mm, though this increases on lower pitches. The side lap on corrugated profiles is one full corrugation (76mm), while on trapezoidal profiles it is one full rib. The direction of side laps should be oriented away from the prevailing weather — in Gippsland, this generally means lapping away from the north-west, as the majority of severe weather arrives from that direction. For tile roofs, the overlap is built into the tile profile — the head lap (vertical overlap) is typically 75mm for standard profiles at standard pitches. Reducing the overlap below the manufacturer's minimum specification compromises the waterproofing integrity of the roof and may void the warranty. Town & Country Roofing ensures all overlaps comply with Australian Standards and manufacturer specifications on every installation.