For most property managers, “peak leak season” doesn’t actually hit with the first cold snap — it arrives later in winter and early spring, after months of freeze-thaw cycles have stressed every weak point in the roof.
If your commercial or industrial buildings have low-slope or flat roofs, winter is one of the most critical times to stay ahead of leaks. A small seam flaw or clogged drain in November or December can turn into a major interior water issue by February or March.
How Winter Really Damages Commercial Roofs Winter damage isn’t just about more rain or heavier snow. It’s about how water behaves as temperatures swing above and below freezing.
The Freeze-Thaw Effect on Commercial Roof Systems
Here’s what happens on a typical low-slope roof in winter:
Moisture gets into small gaps Tiny openings at seams, flashings, fasteners, or around penetrations let in small amounts of water Temperatures drop, water freezes Water expands as it freezes — roughly 9–10%. That expansion acts like a wedge, forcing seams and cracks wider Daytime warmth equals thaw The ice melts, water sinks deeper into the system, and may reach insulation, fasteners, or deck level The cycle repeats. Over days and weeks, this repeated expansion and contraction can:
Open seams in membranes Loosen fasteners Crack or separate flashings Create soft, wet areas in the roof system By the time peak leak season hits, you’re not seeing new problems — you’re seeing months of accumulated damage finally showing up inside the building.Other Winter-Specific Roof Risks
In addition to freeze-thaw cycles, commercial roofs face:
Ponding water that freezes into heavy ice, adding structural load and stressing membranes and seams Clogged drains and gutters that back up water, cause ice dams, and force moisture under flashings Snow and ice movement on metal roofs Wind-driven rain and snow that finds its way into any weakness in the building envelope Many property managers wonder what are scuppers on a roof and why they matter so much in winter. Simply put, what is a scupper is an opening designed to allow water to drain through parapet walls or roof edges. When roof drain scuppers are blocked or undersized, water has nowhere to go, increasing the risk of ponding water on roof surfaces and accelerating damage that leads to leaks.
The good news is that most of the worst winter leaks are preventable with proactive planning.
The 5 Essential Steps Before Peak Leak Season Step 1: Schedule a Pre-Winter Commercial Roof Inspection Your first line of defense against winter leaks is a professional commercial roof inspection
What a Good Winter-Readiness Inspection Should Include
Ask your commercial roofing contractor to:
Inspect the entire roof surface for punctures, blisters, open seams, and worn membrane Identify previous repair areas and check their condition Check flashings Evaluate drainage systems such as roof drains, scuppers gutters Look for ponding water areas and dark spots on the roof Review rooftop equipment supports for sharp edges, shifting supports, or conduit that could wear through the membrane Why Timing Matters
You want this inspection completed before:
Sealants stop curing properly due to low temperatures Snow, ice, and constant moisture make access and repairs more difficult Your maintenance budget is consumed by emergency calls instead of planned work Pro Tip for Property Managers
One of the most common causes of winter leaks on flat and low-slope roofs is poor drainage — and it’s completely preventable.
Why Drainage Is Critical in Winter
When drains and gutters are clogged with leaves, branches, or debris:
Water ponds around drains and low areas That water freezes into heavy ice, stressing the roof system Ice expansion can pry up seams and damage flashings Backed-up water can find its way under membranes and into the building Poor drainage is one of the most common contributors to leaking commercial roofs, especially during repeated freeze-thaw cycles.
Action Items Before Peak Leak Season
Have a qualified team safely:
Remove leaves, branches, packaging, and trash from the roof Clean around all drains, scuppers, and gutters Confirm drain domes or strainers are present, secure, and unclogged Check that downspouts and interior drain lines are flowing properly Verify overflow drains or scuppers are clear Safety Reminder
An issue that feels minor in early fall can become a major leak by late winter or early spring.
Common Vulnerabilities to Address
Open or loose seams in the roof membrane Cracks or gaps in flashings and sealants Blisters, fishmouths, or splits Damaged pitch pans or penetration seals Exposed or backed-out fasteners Soft or low areas that indicate wet insulation Why Temporary Fixes Fail in Winter
Quick patches using incorrect materials or techniques often fail under freeze-thaw stress. Whenever possible:
Use manufacturer-approved materials Follow cold-weather application guidelines Document repairs for warranty purposes Budget Tip
Some roof areas will always be higher risk, especially during winter.
High-Risk Areas to Reinforce
Around drains and scuppers where water concentrates Seams and transitions in ponding areas Walk paths and service routes using walkway pads Metal roof snow and ice management with retention systems When Roof Coatings Make Sense
For some aging low-slope roofs, a professionally installed silicone roof coating system
Step 5: Create a Winter Roof Response & Maintenance Plan Winter-proofing isn’t just about the roof, it’s about how you respond when weather hits Your plan should include emergency contacts, priority buildings, post-storm inspection triggers, interior monitoring procedures, and clear roof access rules Pro Tip
Bonus: Don’t Ignore What’s Happening Inside the Building Winter leaks don’t always appear as obvious drips. Early warning signs include ceiling discoloration, peeling paint near exterior walls, and musty odors. Treat these as early alerts, not cosmetic issues.
Putting It All Together: A Winter-Ready Commercial Roof Checklist Before peak leak season:
A documented pre-winter roof inspection Drains, scuppers, gutters, and roof surfaces cleared Critical repairs completed properly High-risk areas reinforced A winter roof response plan shared with staff
When should I schedule a winter commercial roof inspection?
How often should my commercial roof be inspected?
Are all roof leaks preventable?
What’s the biggest mistake property managers make before winter?
Winter roof leaks are rarely sudden. They’re usually the result of small issues made worse by months of freeze-thaw cycles. Taking a proactive approach now can help property managers avoid costly repairs and disruptions during peak leak season.
WNC Roofing works with property managers and building owners to identify risks early and prepare commercial roofs for winter. Contact us
