TL;DR:
Flat roofs are more vulnerable to snow buildup, ice dams, and drainage issues during Ontario winters. Prevent winter flat roof damage with regular inspections, clear drainage systems, controlled snow removal, and proactive maintenance across the GTA and Hamilton Area.
Winter can be tough on commercial flat roofing systems. Unlike sloped roofs that naturally shed snow, flat roofs tend to hold snow and ice for longer periods. In regions like Toronto, Mississauga, Hamilton, and surrounding areas, heavy snowfall combined with freeze-thaw cycles can quickly turn small issues into costly structural problems.
The good news? Most winter flat roof damage is preventable with proper planning and maintenance.
Below are practical steps to protect your commercial flat roof during winter in the Greater Toronto and Hamilton Area (GTA & GTHA).
1. Schedule Pre-Winter & Mid-Season Roof Inspections
Routine inspections are one of the most important parts of winter roofing maintenance.
Before winter arrives, a professional flat roof inspection should check for:
- Membrane cracks or punctures
- Open seams or flashing gaps
- Drainage blockages
- Soft spots in insulation
- Previous repair areas
During the winter months, additional inspections help identify issues caused by snow loads, ice expansion, or temperature shifts.
In cities like Toronto, Vaughan, Oakville, Burlington, and Hamilton, fluctuating temperatures can accelerate membrane stress. Identifying minor vulnerabilities early prevents major water infiltration later.
2. Keep Drainage Systems Clear
Proper drainage is critical for flat roof performance — especially in winter.
Blocked drains and downspouts allow melted snow to refreeze and create ponding water. Over time, that standing water adds significant weight and weakens the roofing system.
To maintain effective drainage:
- Remove leaves and debris before snowfall
- Ensure internal drains are unobstructed
- Check scuppers and downspouts regularly
- Monitor areas where water typically pools
Commercial buildings across Mississauga, Richmond Hill, Markham, and Milton often experience drainage issues due to rooftop debris accumulation in the fall. Preventative cleaning before winter can dramatically reduce risk.
3. Manage Snow Accumulation Safely
Flat roofs are engineered to handle substantial loads — but excessive snow buildup can still pose risks.
Heavy snowbanks increase structural pressure and can lead to:
- Membrane stress
- Leaks at seams
- Flashing separation
- Sagging sections
- Structural strain
If snow accumulation becomes excessive, professional snow removal may be required. Avoid using sharp tools that can puncture the membrane. Snow-melt systems or heated drainage components may also help reduce buildup on larger commercial properties.
Buildings in Hamilton, Ancaster, Dundas, Stoney Creek, Cambridge, and Kitchener are particularly exposed to heavy lake-effect snowfall and should monitor roof loads carefully.
4. Monitor Freeze-Thaw Cycles
Ontario winters bring repeated freezing and thawing. When daytime melting is followed by overnight freezing, trapped water expands and stresses roofing materials.
Freeze-thaw damage can cause:
- Small membrane cracks
- Seam separation
- Flashing movement
- Surface blistering
Proactive maintenance reduces the likelihood of long-term membrane failure.
5. Check Roof Access Points & Flashing
Mechanical curbs, skylights, vents, and parapet walls are common leak points in winter.
Ensure:
- Flashing is secure
- Sealants are intact
- Rooftop HVAC units are properly sealed
- Expansion joints are flexible
In commercial buildings throughout Vaughan, Woodbridge, Kleinburg, King City, and Guelph, rooftop mechanical systems are often installed on flat membranes. Winter stress can impact these connection points.
6. Protect Your Flat Roof Investment
Flat roofs are built for durability — but winter adds stress.
Proactive winter roofing maintenance:
- Extends roof lifespan
- Reduces emergency repair costs
- Protects insulation and interior assets
- Prevents unexpected operational disruptions
- Improves energy efficiency
For commercial property owners in Toronto, Mississauga, Oakville, Burlington, Hamilton, Milton, Cambridge, Kitchener, Niagara-on-the-Lake, Muskoka, Kawartha and surrounding areas, seasonal roof planning is a critical part of facility management.
Commercial Flat Roof Maintenance in the GTA & Hamilton Area
At The Cedar Cleaners, we provide professional flat roof inspections, maintenance, and winter preparation services across the Greater Toronto and Hamilton Area.
We work with commercial and industrial property owners throughout:
Toronto, Mississauga, Richmond Hill, Markham, Vaughan, Woodbridge, Kleinburg, North York, Oakville, Burlington, Milton, Hamilton, Ancaster, Dundas, Stoney Creek, Cambridge, Kitchener, Guelph, Niagara-on-the-Lake, Muskoka, Kawartha and surrounding communities.
If you want to reduce the risk of winter roof damage and protect your commercial property, proactive maintenance is the smartest investment you can make.