Expansion Joint

All building materials expand when heated and contract when cooled. On a roof, where surface temperatures can range from below zero on a winter night to over 80 degrees Celsius on a dark metal surface in summer, this thermal movement can be substantial. A 12-metre Colorbond roof sheet, for example, can expand by approximately 10mm between winter minimum and summer maximum temperatures. If this movement is restrained by rigid fixings at both ends, the sheet will buckle, oil-can (create visible waviness), or pull screws through the sheeting. Expansion joints in roofing take several forms. On long sheet runs, slotted holes in the fixing brackets allow the sheet to slide as it expands and contracts. On large commercial roofs, physical expansion joints — essentially a raised cap over a flexible gap — are installed at regular intervals to break the roof into manageable sections. On flashing and gutter runs, expansion joints or sliding lap joints allow adjacent lengths to move independently. In Gippsland, where temperature extremes between seasons are significant, thermal expansion management is an important consideration for all metal roofing installations. Town & Country Roofing accounts for thermal movement in every installation by using the correct fixing methods — a combination of fixed and sliding fasteners — and by incorporating expansion provisions in long gutter runs, flashings, and ridge cappings.