Spotting Trouble Before Your Tower Topples
Friday, August 22, 2025
Understanding and Preventing Concrete Silo Deterioration
By Mary Loggan
Concrete tower silos are a defining feature of Ontario’s rural landscape, serving as crucial storage for silage and grain. However, these structures face a persistent threat from within: The gradual but relentless deterioration caused by silage acids. As silos age, the risk of failure grows – a risk that can have devastating consequences for farm operations.
Better Farming recently spoke with Tim Koch of Koch Construction in Shakespeare to understand how monitoring, detecting, and addressing deterioration is essential for safety, productivity, and the long-term value of these agricultural assets.
Importance of monitoring
Koch, who has decades of experience repairing silos across Ontario, offers a candid perspective on why monitoring is often overlooked. “Farmers don’t often check the bottom of the silos where the juices collect,” he says.
“This is a critical oversight, as the base is where the highest concentration of silage acids and moisture accumulates.”
He points out that it can also sometimes be difficult for farmers to completely inspect the inside.
“When producers don’t get their silos emptied fully or haven’t been emptied in the last 10 years, acids have prolonged contact with the concrete, compounding the damage.”
Routine monitoring is not just a best practice – it’s a necessity, he says.
A report from OMAFA highlights that most concrete tower silos deteriorate due to the attack of silage acids, especially lactic and acetic acids produced during fermentation.
It points out that these acids react with the Portland cement in concrete, weakening the structure and corroding reinforcing steel. The consequences of neglect can be catastrophic, ranging from structural collapse to loss of feed, livestock, and even lives.
Koch recalls a recent incident: “Worst-case, the silo falls over. Last year in Mitchell, that’s exactly what happened.”
Many farmers, he says, are unaware of the true condition of their silos until a major failure occurs.
“You don’t know the condition until you see it.”
For those who feed wetter silage, the risks are even greater, as higher moisture content leads to more acid production and faster deterioration.
Another challenge is the lack of thorough cleaning. “No one really cleans with a pressure washer,” Koch explains. “We have to pressure-wash to see what’s going on.”
Tim Koch photo
He emphasizes that “most often, things happen on the inside which you can’t see on the outside.” Sometimes, the only clue is when “you can see daylight through the walls” – a clear sign that the structure is dangerously compromised.
Koch stresses the importance of annual inspections, especially when the silo is empty.
“Do it once a year if you can – check the inside structure, check the cables, and check the pulleys are turning, and that everything is working smoothly.”
Signs of degradation
Recognizing the signs of concrete silo deterioration is crucial for timely intervention. According to an OMAFA report, the most common and dangerous form of damage is caused by silage acids attacking the concrete and reinforcing steel.
The damage is most severe at the bottom of the silo, where gravity brings all the juice down, concentrating the acids and moisture.
Koch describes what to look for during inspections: “You start to see rebar on the inside. Most of the time, it’s the bottom half that’s affected.”
He adds, “When you’re using the loader and it’s throwing out gravel, or you notice the walls are pitted and the door frames are getting eaten away, those are big warning signs.”
He draws a parallel to aging vehicles: “Most concrete silos were often poured in the 1970s and 1980s – it’s like an old car you’ve been driving, and you know there will be rust.”
According to OMAFA, other key signs of degradation include:
Cracking: Especially at the base or around doors, indicating stress or loss of structural integrity;
Spalling and flaking: Pieces of concrete breaking away, particularly near the base, suggest acid attack and internal weakening;
Rust stains: Indicate corrosion of reinforcing steel inside the concrete, often visible as streaks on the exterior;
Bulging or out-of-plumb walls: Any visible distortion is a serious warning sign that the structure may be failing;
Water seepage: Persistent dampness at the base suggests acids and moisture are penetrating the concrete, accelerating deterioration;
Loose or missing hardware: Corroded or missing door frames, hoops, or reinforcing bands compromise stability;
Visible rebar or daylight: In severe cases, you may see rebar exposed or even daylight through the walls.
Koch also highlights the importance of proper drainage: “Silos that don’t have a good working drain have more problems. Drains help keep moisture and liquid down, so the silo lasts longer.”
He advises farmers, “Don’t fill it too wet, and try to get it empty every couple of years to see the bottom. That’s when you need to check and inspect conditions.”
Demolition versus repair
When significant deterioration is detected, farmers face the difficult decision of whether to repair or demolish the silo.
OMAFA’s guidance suggests that repairs are possible when damage is localized and the overall structure remains sound.
Common repairs include applying acid-resistant coatings, patching cracks and spalls, replacing corroded hardware, and improving drainage. All repairs should be guided by professionals, especially for older or extensively damaged silos.
Koch agrees and explains, “When it starts to lean, it often needs to be repaired at the base.
‘When it starts to lean, it often needs to be repaired at the base.’ -Tim Koch photo
“Older condition blocked silos are usually done for, but poured silos most of the time can be fixed.” However, he cautions that “if you’ve already had it fixed several times, you need to weigh the costs.
“Most of the time, they can be fixed, but there’s a point where demolition makes more sense.”
“When cracks are wide or numerous, there is significant bulging, or reinforcing steel is extensively corroded, demolition may be the only safe option.”
However, he says that most silos he sees today have not reached that point, and repair for future use is often the best option for producers.
“With repairs, you can get many more productive years of use, which is the most beneficial for farmers. Every operation is unique, so in the end, you need to do what suits your farm the best.”
He acknowledges that “sometimes it can be complicated to know for sure what to do, so I always encourage producers to reach out.
“If there’s any uncertainty, especially when the silo is empty, it never hurts to have a professional take a look.” BF