Like all structures, silos degrade over time. This natural and inevitable deterioration can lead to safety hazards such as falling debris, leaks, wall failure, roof failure, and/or structural failure.
When it comes to the silo structure, the roof and its design is a crucial component. In addition to this, proper maintenance of the silo roof is a requirement but may pose a significant challenge. Many areas that may require repair are not readily visible and often structural damage is not noticed until a significant failure has occurred, the roof has settled, or the risk of impending total failure has been reached.
Leaking roofs can lead to contamination of stored materials which impact product quality. Water penetration also leads to corrosion of metal silo components like roof beams – an issue that can lead to total roof failure if not addressed. Roof beams are a frequent area of corrosion, or concrete deterioration often due to roof leaks. Spalling of concrete roof beam pockets can further expose beams and lead to eventual roof failure or collapse.
Signs of ponding water on the silo roof (as well as signs of cracking or peeling in the roof-top coating) are indicators that your roof structure is at risk. Regular ponding on the silo roof lowers the lifespan of coating membranes and can lead to deterioration and leaks. More seriously, ponding water is usually caused by issues with the supporting roof beam, potentially indicating severe underlying structural problems. Left unaddressed these problems become costlier to correct and increase liabilities.
Problems with silo roof slabs are mostly related to critical structural conditions such as material buildup, the addition of heavy equipment to the original design or flaws with the original design. The roof beam supports should have been designed to accommodate for thermal expansion and vibration from equipment and cycling of the silo by filling and discharging. This is accomplished by allowing the roof beam base plates to freely slide in the longitudinal direction over an embedded steel plate on the wall beam pocket.
The embedded plates that support the roof beams are usually involved in the failure process. Weather and temperature changes, vibration, and movement of beams cause the concrete walls to deteriorate faster around the beam pockets than the rest of the silo walls. Such deterioration leads to spalling and loosening of the bond between the embedded steel anchors and the concrete walls. When such conditions occur, the roof supporting steel beam will eventually rest on unprotected concrete. The constant thermal expansion and contraction of the beam, combined with the dead and live loads applied to it, creates a grinding force between the beam’s base plate and the silo wall. Often times this will lead to breakage of part of the silo wall immediately under the beam. When this happens, the beam shifts downward until it rests again on a solid portion of the silo wall.
Beam pockets are a critical point on the silo as these roof beams hold up the roof slab and all the necessary equipment to operate the bulk storage system. One of our recent case histories examine a silo roof beam bearing repair.
Regular inspections of the underside of the silo roof along with all equipment are imperative to eliminate potential failures in any production system, including silos. Proper silo roof design is critical. While roofs are designed to hold equipment, they are not designed for excessive amounts of material. If a loading system fails or a silo is overfilled, creating bulk material on the roof, unseen damage can result and compromise the entire structure.
To learn more, be sure to check out our full library of silo construction videos on silo maintenance, repair and inspection on