Metal roofs are designed to be a low-maintenance protection from inclement weather. While some metal roofs may last for decades without maintenance, the screws that anchor the metal roof material to the building may work loose. There are several reasons why the screws on a metal roof may come loose; understanding what causes loose screws can help minimize how often a roof requires repair.
Metal roofs are prone to expansion and contraction based upon the temperature outside a home. As a metal roof heats up, the entire roof expands. Likewise, cold temperatures outside a home cause the roof to contract. These expansion and contraction cycles will cause strain on the screws that hold the roof material to the building, causing those screws to loosen.
Compression Due to Loading
Homes in climates subject to heavy snow or ice loads may experience material compression. If the snow or ice compresses the roof material enough, it will sink lower than the screws, exposing those screws. When the snow or ice melts or slides off the roof, the roof material will spring back into shape. These compression and release cycles can cause strain on the screws, causing them to loosen.
Roof screws are installed with a rubber gasket between the screw head and the roof material. This gasket prevents water from seeping into the hole in the roof material where the roof screw is installed. Over time, these gaskets can deteriorate. A gasket that has deteriorated completely will loosen the screw somewhat.
Water Damage to Underlying Material
If water has seeped under the roof material, the underlying material may become damaged. Screws may not be able to grip the underlying material enough to properly hold the metal roof down. If the underlying material has rotted or corroded sufficiently, the screws holding the metal roof will become loose.