expansion cleat
A cleat designed to accommodate thermal movement of metal roof panels.
expansion cleat: lets metal roofs move without tearing
An expansion cleat is a fastening bracket that allows metal roof panels to slide slightly without splitting or buckling as temperature changes cause the metal to grow and shrink. Metal expands when heated and contracts when cooled, sometimes by fractions of an inch across a large roof. A standard rigid fastener locks the panel in place, making movement impossible and creating stress that eventually cracks or tears the metal. An expansion cleat solves this by holding the panel securely while permitting controlled lateral movement along its length.
The cleat works by using a slot or elongated hole in the bracket instead of a fixed bolt hole. The fastener passes through this slot loosely enough that the panel can slide back and forth by typically one quarter to one half inch in each direction. Some designs use a factory-formed slot; others use a spring-loaded clip that grips the panel while allowing it to shift. The cleat itself is anchored to the roof deck or purlin with fixed bolts, staying put while the panel flexes beneath it.
Materials and placement
Expansion cleats are most common on standing seam metal roofs and through fastened panel systems. They are usually made from galvanized or stainless steel to match the roof panels and resist corrosion. The cleat is positioned at one end of each panel run, typically toward the eave or ridge, at intervals determined by the panel manufacturer and the expected temperature range of the climate. Roofs in regions with large seasonal swings, such as northern climates, require more cleats spaced closer together than roofs in milder zones.
Failure to use expansion cleats, or using them incorrectly, results in fastener pull-through, punctures in the panel, and panel buckling that can advance to leaks. Oversized panels or those installed in high-temperature environments like industrial buildings or dark-colored residential roofs run the greatest risk if not given adequate room to move. The cleat is a small detail but one that extends the functional life of the roof system by years.