Panel laps (end and side laps)
All metal roof systems are composed of a series of mostly rectangular placed panels, of a particular profile, gauge and finish that must be interlocked or lapped at the perimeter end & side laps. These overlaying end & side laps have a butyl elastomeric tape mastic sandwiched between them to form a watertight seal. Industrial metal roof fasteners, with fitted EPDM washers, are installed to ensure a secure and integral nesting of the perimeters.
The majority of commercial, industrial, manufacturing and warehousing metal roof systems are typically composed of 26 or 24 gauge Galvalume metal panels, cold roll formed in 12” up to 36” widths in lengths up to 60’. The panel profiles are usually of the standing seam (trapezoidal rib or “L”) or conventional “R” type.
Smaller buildings with short eave to ridge lengths may not require panel end laps and only panel side laps are required for sealing, nesting and fastening.
Vertical or horizontal: transition and expansion joints and step flashing
Transition and expansion joints come in many sizes, configurations and different materials. They are placed either horizontally or vertically (parallel to the roof pitch) to accommodate building additions, building modifications or the sheer size of a roof. In the case of very large roofs architects & engineers will call out expansion joints or step flashing to break the continuity of thermally induced stress that can elevate beyond design limits without such flexible connections. The expansion and contraction of metal roof panels as propagated through normal environmental thermal cycling is controlled to acceptable levels with such devices.
The constant movement of metal roof systems, even when fitted with flexible joints and flashings, require vigilance via routine inspections and associated preventive maintenance that will serve to extend roof system longevity.
Pipe, stack, vent and equipment curb flashing
Most all metal roof systems have pipe, stack or vent penetrations through their metal panels and many roofs have equipment mounted curb installations. Because these components penetrate the roof panels their flashing and curb flanges must be extremely well sealed to obtain a watertight system. Any fasteners installed at the perimeters must have integral EPDM washers and be installed perpendicular to the flange surface.
Ridge caps
Ridge caps connect together opposing roof slope panels at the apex. They can be of the formed or flat style. Because ridge caps consist of extensive panel to component overlapping proper sealing with or sithout closures is paramount for a watertight seal. Ridge caps installed on SSR (floating type standing seam) metal roof systems incur thermally induced forces driven by panel growth and shrinkage during these cycles. Constant vigilance via routine inspections and associated preventive maintenance are important aspects to roof system longevity.
Rake flashing & wall flashing (including high eave)
Where building end walls and metal roof systems terminate along a line of intersection rake flashing is used to connect the perpendicular planes together to obtain a watertight interface. Because the two planes at fastened to unrelated sub-structures and the fact that the roof and wall expand and contract independent of one another during thermal cycling the rake flashing usually incurs higher stress levels. Therefore it is prudent to schedule routine inspection and preventive maintenance to ensure that the line of interface remain whole and integral for a watertight connection.
The same scenario can be applied for roof to wall flashing where relative movement between planes is normal under thermal cycling conditions. The integrally coupled roof to wall via a metal flashing, closures and sealant incur thermally induced forces that can loosen fasteners. Routine inspections and associated preventive maintenance enhance the integrity of these components and ensure roof system longevity.
Eave, valley and internal gutters
Gutters, by the very nature of their location, situated at the lowest point, where all water collects and subsequently evacuates the roof system, is a place where moisture infiltration potential is maximized. Panel closure systems with appropriately installed sealant and fasteners at the gutter flanges must be homogeneous and exhibit high degree of continuity for an integral and watertight connection. Routine inspection and preventive maintenance performed on: eave, valley and internal gutter system connections, to roof panels, are vitally important to maintaining a watertight roof.