The #1 Cause of Commercial Roof Failure (And How to Prevent It)

Flashings Fail First: Why 90% of Commercial Roof Leaks Start at the Details

When commercial roofs fail, most people immediately think of storms, age, or surface damage.
But the truth is far more subtle, and far more important for property managers and building owners to understand.

Over 90% of commercial roof leaks originate at the flashings, not in the middle (or “field”) of the roof.
Flashings are the transition points: where the roof meets walls, parapets, HVAC curbs, pipes, vents, and edges.
They’re also the first areas to break down—and the first indicators of future system failure.

If you own or manage a building, knowing why these areas fail can save you tens of thousands of dollars in long-term repairs and early replacements.

What Exactly Are Flashings—and Why Are They So Vulnerable?

Flashings are designed to seal and protect the most complicated parts of your roof.
They cover:

• Parapet walls

• Roof edges

• HVAC curbs and mechanical units

• Pipes and penetrations

• Pitch pans

• Skylights and transitions

• Termination points

While the field membrane lies mostly flat and stable, flashings experience:

• Daily expansion and contraction

• Structural movement

• Thermal stress

• Uplift pressure

• Foot traffic from maintenance crews

• UV exposure and material fatigue

This combination makes flashings the most stressed components of any commercial roofing system.

The Daily Stress Cycle That Leads to Failure

In South Florida, temperature swings can be extreme—cool mornings followed by intense midday heat.
This causes the roofing system to expand and contract constantly.

Here’s what happens:

1. Heat causes flashings to stretch

Fasteners pull upward, seams are strained, and adhesives weaken.

2. Cooling snaps everything back

That “snap-back” effect repeats thousands of times per year.

3. Movement fatigues the materials

Eventually:

• Sealants crack

• Adhesion breaks down

• Membranes separate

• Fasteners back out

• Micro-gaps form long before leaks appear inside

This damage is slow, silent, and invisible from the ground—making it easy for property managers to miss.

Why PMs and Building Owners Rarely Catch Flashing Failure Early

Because flashing failures start internally, many systems look perfectly fine on the surface—right up until the leak hits the interior.

By the time water enters the building:

• The flashing has usually been failing for months (or years)

• Insulation may already be saturated

• Mold or structural damage could be developing

• Extensive repairs are often needed

That’s why early detection is everything.

What Causes Flashing Failure Most Often?

Here are the most common culprits:

1. Thermal Movement

The #1 cause—especially in South Florida’s climate.

2. Poor Installation Practices

Incorrect adhesion, improper fastening, or insufficient termination bars.

3. Aging Sealants

Sealants dry out and lose their elasticity.

4. Foot Traffic

HVAC and maintenance crews often step on flashings without realizing the damage.

5. Water Ponding at Transitions

Standing water accelerates weakening.

6. Incompatible Materials

Different membranes may expand at different rates, causing separation.

How to Prevent Flashing Failure Before It Becomes a Leak

Prevention is the most cost-effective roofing strategy for commercial properties.
Here’s what every property manager should implement:

✔ Annual flashing inspections

(Not just general roof inspections—these must specifically evaluate transition points.)

✔ Resealing penetrations and strengthening transitions

A small fix today prevents major failures tomorrow.

✔ Reinforcement in high-movement areas

Especially at parapets, curbs, and corners.

✔ Fastener checks and re-securement

One backed-out fastener = a future leak.

✔ Proper termination and edge metal integrity checks

✔ Post-storm evaluations

Even if the roof appears fine.

Why Partnering With the Right Roofing Contractor Matters

Not every roofing contractor understands the complexity of flashing systems.
And not every contractor takes the time to evaluate them thoroughly.

At Encore Roofing Services, we focus on the details that protect the asset:

• Flashing-by-flashing evaluations

• Thermal movement analysis

• Integrity checks on curbs, walls, and penetrations

• Fastener and seam reinforcement

• Detailed reporting for property managers

• Preventative strategies that extend the life of the system

Because roofing isn’t just installation—it’s engineering, foresight, and protection.

The Bottom Line

Commercial roof leaks rarely start in storms.
They rarely start in the field of the roof.
They almost always start at the flashings—long before water enters the building.

Understanding where failures truly originate empowers property managers and owners to:

✔ budget smarter
✔ prevent leaks
✔ extend roof life
✔ reduce emergency repairs
✔ protect the building long-term

Strong roofs start at the details.
And flashings—more than anything else—are the details that matter.

Encore Roofing Services

Serving South Florida | CCC1336301
Every roof deserves an Encore.