If you’re dealing with an intermittent roof leak on your commercial building, you’re not alone, and you’re not imagining it. Many property owners are surprised when a roof leaks only under specific weather conditions or seems to fix itself between storms. It’s frustrating, confusing, and often difficult to diagnose without a thorough inspection.
So, what causes a roof to leak sometimes but not all the time? The answer often lies in environmental conditions, roof design, and hidden weaknesses that only show up under certain stressors. In this blog, we’ll break down the common causes of roof storm damage that may result in occasional leaks, what to watch for, and how to address them before they turn into serious damage.
The Nature of Intermittent Roof Leaks
Unlike constant leaks, intermittent leaks usually don’t follow a predictable pattern, making them harder to catch and even harder to fix. They may only show up:
- During heavy rain or snowmelt
- When winds blow from a certain direction
- After freeze-thaw cycles
- Under pooled water or clogged drainage systems
This kind of leak might not leave an immediate stain or puddle. Instead, you might notice damp insulation, a musty odor, or a slight discoloration on ceiling tiles. By the time it’s visible, damage may already be underway.
Common Causes of Occasional Leaks in Commercial Roofs
1. Wind-Driven Rain
If your building only leaks when the wind picks up, it’s likely due to wind-driven rain infiltrating vulnerable spots. High winds can force ponding water under flashing, behind wall panels, or beneath membranes where water wouldn’t normally reach.
On flat and low-slope roofs, this is especially common around:
- Rooftop HVAC units
- Skylights and drain
- Parapet walls and perimeter flashings
- Seams between roof sections
Even if your roofing membrane is intact, water can sneak in through the smallest openings when pushed horizontally by strong gusts.
2. Freeze and Thaw Cycles
Colorado’s wide temperature swings are notorious for causing roofing headaches. During winter, water can seep into small cracks or seams, freeze overnight, and expand, widening the opening. When it thaws, it may start leaking inside.
These leaks often appear in:
- Cracked flashing
- Gaps around penetrations
- Split seams in aging membranes
- Ponding areas where water doesn’t fully drain
If you only notice leaks after a warm-up following a cold snap, freeze-thaw movement is likely to blame.
3. Clogged or Inadequate Drainage
Flat roofs depend heavily on well-designed and properly functioning drainage systems. If your drains are clogged with debris, leaves, or snowmelt, water can pool and find its way into weak spots, even if your roof appears watertight.
These types of leaks typically show up:
- After steady, prolonged rain
- When snowmelt overwhelms drain capacity
- In low spots near clogged scuppers or drains
If your leak disappears after water finally drains off the roof, drainage should be one of the first things you inspect.
4. Hidden Roof Damage
Not all damage is visible at first glance. Your roof could have:
- Blisters or bubbles beneath the membrane
- Delaminated insulation
- Loose fasteners under metal panels
- Hairline cracks near flashing
These problems might not leak under light rain but can allow water infiltration when pressure builds, such as during storms or snowmelt.
Routine inspections help detect these hard-to-spot issues before they develop into larger structural problems.
5. Roof Penetrations and Equipment
Commercial roofs often have multiple penetrations: HVAC systems, vents, plumbing stacks, and electrical conduit mounts. Any of these can be a weak point, especially if the flashing around them has degraded.
If the leak is coming from a specific area inside your building, like near a conference room or storage space, it may correspond with a poorly sealed roof penetration directly above.
Seasonal expansion and contraction can also loosen flashing or sealants, causing leaks to appear sporadically.
Why Timing and Weather Matter
Many building owners call for help during a dry spell, only to find that no active leak is present when the roof is inspected. This delay in symptoms can make pinpointing the cause more challenging.
That’s why at Integrity Pro Roofing, we often recommend:
- Documenting when and where leaks occur
- Noting weather conditions at the time (rain, snow, wind direction)
- Taking photos of interior damage for reference
- Scheduling inspections shortly after the leak occurs
The more details you can provide, the easier for professionals to trace the problem and provide a long-lasting fix.
The Risks of Ignoring Occasional Leaks
Even small, irregular leaks can have big consequences over time. Water that enters and dries repeatedly may never trigger visible damage until it has compromised:
- Interior drywall or ceiling tiles
- Insulation, reducing energy efficiency
- Steel beams or trusses (rust)
- Electrical systems hidden in ceiling spaces
- Roof decking or underlayment
In commercial buildings, even a slow leak can increase liability, disrupt operations, or damage valuable equipment and inventory.
Prevention Is the Best Strategy
The best way to manage leaks is to prevent them before they start. Our commercial clients benefit from ongoing maintenance plans that include:
- Biannual inspections
- Drain clearing and debris removal
- Flashing and sealant touch-ups
- Thermal scans to detect hidden moisture
- Detailed condition reports with photos
Routine maintenance is especially critical for flat roofs, where water has nowhere to go if your system isn’t functioning perfectly.
When to Call a Professional
If you’ve noticed a leak that only happens “sometimes,” don’t wait for it to become a regular issue. The sooner you have it evaluated, the more likely you’ll avoid:
- Disruption to your business
- Extensive structural damage
- Costly emergency repairs
Whether you need a full roof assessment, targeted repair, or guidance on replacement, our team is here to help.
Talk to Integrity Pro Roofing Today
At Integrity Pro Roofing, we understand that even “minor” leaks can lead to major problems. That’s why we provide clear answers, professional inspections, and commercial roofing solutions built to last in Colorado’s extreme climate.
We serve commercial property owners, facility managers, and business leaders across the Denver metro area with a focus on flat and flat metal roofing systems.Need help with a leak that just won’t behave? Let’s get to the bottom of it on your schedule, with zero pressure. Contact us today to request your complimentary digital roof analysis and expert consultation.
