If you’ve managed a commercial property in Southern Ontario through the winter, you already know how hard snow and ice can be on a roof. Flat roofs in particular take a beating. The weight of snow, the freeze-thaw cycles, and the constant moisture put pressure on materials and structures that weren’t designed to carry that kind of abuse forever.
The tricky part? Most warning signs of winter damage don’t jump out right away. They show up quietly in ceiling tiles, drainage systems, or small shifts in the roof deck before they turn into costly repairs. Over the years, we’ve seen building managers miss early signals, only book commercial roofing services once leaks were already dripping on office equipment or tenants were complaining.
Below are the top warning signs we recommend keeping an eye out for this winter, along with what they mean, and what you can do to prevent them from getting worse.
1. Sagging or Bowing Roof Sections
When snow builds up, especially during back-to-back storms, the extra weight can cause parts of the roof to sag. It doesn’t always collapse right away, but sagging is the early red flag. We’ve seen this most often on older buildings where the support structure is already under strain.
Why it’s a problem:
A sagging roof deck means the load is too much for the structure. Left alone, it can compromise the integrity of the roof or even lead to partial collapse.
What to do about it:
- Schedule a professional inspection after major snowfalls.
- Clear snow from the roof safely – always book a professional to do this.
- Consider adding tapered insulation during your next roofing project. It not only helps with drainage but can also spread loads more evenly.
2. Ice Dams and Blocked Drainage
Flat roofs rely on clear drains and scuppers to move water off the surface. When snow melts and then refreezes, water can pool and create ice dams. We’ve seen drains frozen solid, with water backing up and sitting on the roof for days.
Why it’s a problem:
Standing water seeps into seams and small cracks. Once it freezes again, it pushes those gaps wider, making leaks inevitable.
What to do about it:
- Have drains and scuppers checked and cleared regularly.
- Make sure heat loss from the building isn’t causing uneven melting.
- Get a roofing contractor to inspect and reseal vulnerable areas before winter hits.
3. Water Stains or Leaks Inside the Building
One of the most common calls we get in winter comes after someone notices ceiling tiles sagging or water dripping inside. By that point, the problem had started weeks earlier on the roof.
Why it’s a problem:
Interior leaks don’t just damage finishes. They can take out insulation, wiring, and even compromise structural elements if left untreated.
What to do about it:
- Don’t just replace the tile and forget about it. Find the source.
- Have a professional trace leaks to their entry point on the roof.
- Schedule regular mid-winter inspections – not just in the spring.
4. Cracks in Walls or Ceilings
This is one thing people don’t always connect to roofing. We’ve walked into commercial spaces where the manager was worried about drywall cracks, not realizing they were a symptom of roof stress.
Why it’s a problem:
Shifting loads on the roof can push down on walls, causing cracks inside. It’s an early signal that something above isn’t holding up as it should.
What to do about it:
- Treat structural cracks seriously.
- Call in both your roofer and, if needed, a structural engineer.
- Keep up with snow removal and inspections to prevent overload.
5. Damaged Gutters and Eaves
Even on flat roofs, eaves and edge details take a hit in winter. Heavy icicles or expanding ice can tear gutters away from the building.
Why it’s a problem:
Once gutters pull loose, water flows where it shouldn’t – down walls, into foundations, and around entrances. That creates safety hazards and building damage.
What to do about it:
- Inspect gutters and downspouts after each major storm.
- Don’t chip away at ice – it often does more harm than good.
- Get a professional crew to handle ice safely and repair damage right away.
6. Sprinkler Heads or Ceiling Tiles Sagging
This one often surprises people. If your fire suppression system or drop ceiling tiles are sagging, it’s often because the roof above is stressed. We had a client last winter whose sprinkler pipes nearly burst because of the extra pressure from the snow load.
Why it’s a problem:
It’s both a roof issue and a safety issue. Sagging sprinkler heads can signal dangerous stress on the structure.
What to do about it:
- Never ignore changes in your ceiling system.
- Call a roofing professional to check for load issues.
- Keep up with proactive snow removal before systems are put at risk.
- Staying Ahead of Winter Roof Damage
The best prevention is planning ahead. Waiting until after a storm to act usually means waiting in line with every other business owner who’s just discovered a problem. By scheduling flat roof inspections, clearing snow and ice safely, and keeping drains clear, you can avoid the majority of winter roof failures we see each year.
At Industrial Roofing Services Limited, we’ve been working on commercial flat roofs in Toronto and across Southern Ontario for over 45 years. We know the warning signs, and we know how to address them before they turn into major disruptions. Our team is fully licensed, insured, and trained to handle everything from routine maintenance to emergency repairs – all with strict safety standards in place.
If you manage a commercial property and want to make sure your roof is ready for winter, reach out for a free consultation. We’ll walk you through what to watch for and build a plan that keeps your building safe, dry, and open for business all season long.