Commercial metal roofs in Calgary are built to last—but constant temperature swings, wind, snow, and hail eventually take their toll. Over time, seams open up, fasteners back out, sealants dry and crack, and suddenly a “lifetime” roof is creating leaks over offices, inventory, and production areas.

The good news: many leaking metal roofs don’t need a full tear-off and replacement. With a smart repair and retrofit strategy, you can stop leaks, improve performance, and extend service life—often at a fraction of replacement cost.

This guide explains why metal roofs leak in Calgary, what repair and retrofit options exist, and how CMP Roofing helps you decide between repair, retrofit, coatings, or full replacement when necessary. For a broader overview of our capabilities, see our Commercial Roofing Services at:

Why Commercial Metal Roofs Start Leaking in Calgary

Metal roof leaks rarely come from one single defect. They tend to develop slowly from a combination of age, movement, and weather.

Calgary-Specific Stress Factors

  • Freeze–thaw cycles and Chinooks
    Rapid temperature swings cause metal panels to expand and contract. Over time, this movement stresses seams, fasteners, and flashings.
  • Snow and ice
    Snow loads, ice dams, and sliding snow can damage panels, displace sealants, and stress seams and flashings.
  • Hail and wind
    Hail can dent panels and damage protective coatings. Wind can work fasteners loose and push water into vulnerable areas.

Common Metal Roof Leak Sources

  • Backed-out or missing fasteners
  • Failed gaskets on exposed fasteners
  • Open panel seams and laps
  • Deteriorated sealant at end laps and penetrations
  • Poorly detailed or aged flashings at walls, skylights, and equipment
  • Rusted-through panels or gutters

A thorough commercial roof inspection is the first step to understanding which of these are at play on your building. For a detailed checklist of what inspectors look for, see:

When Repair & Retrofit Makes Sense vs Full Replacement

Not every leaking metal roof needs a brand-new system. Repair and retrofit options are often ideal when:

  • The metal panels are structurally sound
  • Leaks are mostly at seams, fasteners, or details
  • Rust is localized, not widespread
  • The building owner wants to extend life another 10–20 years before full replacement

Full replacement becomes more likely when:

  • Panels are heavily rusted or structurally compromised
  • The roof has been repeatedly patched without lasting success
  • Insulation and underlayment are saturated
  • The overall system is at end-of-life

For guidance on when it’s time to move to replacement instead of repair, pair this article with:

Targeted Metal Roof Repairs: Tackling the Common Leak Points

CMP Roofing starts with targeted repairs to address obvious and high-risk defects.

Fastener & Gasket Repairs

On many metal roofs, exposed fasteners are a major leak source:

  • Fasteners can loosen over time from movement and wind uplift
  • Gaskets dry, crack, or compress and stop sealing against the panel

Typical repairs include:

  • Re-torquing or replacing loose fasteners
  • Upgrading to oversized fasteners where holes have elongated
  • Installing fasteners with high-quality, UV-resistant gaskets

Seam and Lap Sealing

Panel seams and end laps are critical leak points:

  • Over time, movement and weather break down original sealants
  • Water starts wicking into panel overlaps and under panels

We may:

  • Clean and prep laps and seams
  • Install new high-performance sealants and reinforcement where needed
  • In some cases, add cover plates or retrofit details over chronic problem seams

Flashing and Penetration Repairs

Most persistent leaks occur at:

  • Wall-to-roof transitions
  • Skylights, vents, and pipe penetrations
  • Curbs for HVAC and mechanical equipment

Repairs often include:

  • Reworking or replacing metal flashings
  • Installing new boots and penetration flashings
  • Adding or replacing sealant and reinforcement where movement is expected

For step-by-step guidance when you first notice leaks, see:

Retrofit Option 1: Metal Roof Coatings for Waterproofing & Life Extension

When the metal roof is still structurally sound but showing widespread minor defects, a coating system can be an excellent retrofit.

How Coatings Work on Metal Roofs

After localized repairs and prep, a coating system:

  • Bridges small gaps and fastener heads
  • Provides a monolithic, waterproof surface over panels and seams
  • Protects against UV and weathering

For metal roofs, the most common coating chemistries are:

  • Silicone
    Excellent for UV resistance and ponding tolerance; strong choice where standing water can occur at low-slope metal transitions.
  • Acrylic
    Cost-effective, reflective, good where drainage is strong and ponding is limited.
  • Polyurethane
    Very tough and abrasion-resistant; often used in high-traffic or industrial environments, sometimes in combination with silicone or acrylic topcoats.

A detailed comparison of these options is covered in:

When Coatings Are a Good Fit for Metal Roofs

Coatings often make sense when:

  • Panels are not structurally rusted through
  • The roof is mostly dry below the metal skin
  • The owner wants a 10–20 year extension rather than a full replacement
  • Tenants and operations can’t easily tolerate a full tear-off

Coatings are usually bundled into a maintenance plan so that small issues are caught early. See:

Retrofit Option 2: Metal Roof Overlays & Conversions

In some cases, the best retrofit is to convert the metal roof into a new low-slope membrane system without tearing everything back to structure.

Metal Roof with Low-Slope Membrane Retrofit

A common approach involves:

  1. Installing flute-fill or rigid insulation between and over the metal ribs
  2. Adding additional insulation to meet current R-value requirements
  3. Installing a new membrane (often TPO or SBS modified bitumen) over the new substrate

Benefits:

  • Dramically improves thermal performance
  • Creates a continuous, smooth surface for a membrane roof
  • Reduces the risk of chronic leaks at panel seams and fasteners
  • Can be done with minimal disruption to interior operations compared to full structural replacement

To compare TPO, SBS, and EPDM systems in Calgary’s climate, see:

Metal-Over-Metal Retrofits

On some sloped roofs:

  • A new metal system can be installed over the existing panels with properly designed sub-purlins and insulation
  • This approach preserves the look of metal roofing while upgrading performance and correcting details

CMP Roofing assesses which retrofit strategy best matches your building, budget, and long-term plans. All of these options tie back into our service offerings at:

Dealing with Rust, Condensation & Building Movement

Metal roofs face a few unique issues that must be addressed in any repair or retrofit plan.

Rust and Corrosion

Spot rust is common on older metal roofs, especially around fasteners and panel edges.

CMP Roofing may:

  • Mechanically clean and treat rusted areas
  • Replace severely rusted panels or details
  • Apply compatible primers before coating or retrofitting

If rust is widespread and panels are structurally compromised across large areas, it’s a strong indicator that full replacement or conversion may be the best option.

Condensation and Insulation

Metal roofs can experience interior condensation when:

  • Warm, moist air from inside the building reaches the underside of cold metal panels
  • Insulation or air/vapour control layers are missing or underperforming

Retrofits that add insulation and improve the assembly can:

  • Reduce condensation risk
  • Improve energy performance
  • Stabilize interior comfort

Expansion Joints and Movement Joints

Calgary’s temperature swings demand room for movement:

  • Where roofs change direction, elevation, or material, expansion joints may be needed
  • Poorly designed or aged joints are common leak sources

As part of repair or retrofit, CMP Roofing will evaluate whether additional movement joints or improved details are required to handle long-term expansion and contraction.

Inspections & Maintenance: Keeping Metal Roofs Leak-Free

Even after repairs or retrofits, metal roofs need ongoing inspections and maintenance.

Typical maintenance tasks include:

  • Checking and re-torquing exposed fasteners as needed
  • Inspecting and maintaining sealant at seams and penetrations
  • Clearing gutters and downspouts to protect drainage paths
  • Inspecting after major hail or wind events

These activities are built into our commercial maintenance plans. For a framework, see:

If your roof has experienced hail, it may also be worth pairing this with:

When It’s Time to Move From Retrofit to Full Replacement

Repair and retrofit can add many years to a metal roof’s life, but at some point, replacement becomes the most responsible option.

Warning signs include:

  • Extensive structural rust or panel perforation
  • Multiple prior retrofits or coatings that have failed
  • Widespread insulation or deck moisture issues
  • Significant movement-related damage at many details

At that stage, CMP Roofing will help you plan a full system replacement, often converting to a high-performance TPO, SBS, or EPDM membrane system or a new engineered metal assembly. For replacement planning, see:

How CMP Roofing Approaches Metal Roof Repair & Retrofit in Calgary

When you contact CMP Roofing about a leaking commercial metal roof, we typically:

  1. Gather history: leak locations, age, prior repairs, and building use
  2. Perform a commercial roof inspection focused on seams, fasteners, flashings, drainage, and panel condition
  3. Document findings with photos and a clear condition summary
  4. Present options, which may include:
    • Targeted repairs
    • Coating-based restoration (silicone, acrylic, polyurethane)
    • Overlays or conversions to membrane systems
    • Full replacement where necessary
  5. Develop a maintenance plan to protect your investment going forward

This integrated approach draws from everything we do across inspections, maintenance, coatings, and replacement services:

Next Steps: Get a Metal Roof Repair or Retrofit Assessment in Calgary

If your commercial metal roof is leaking—but you’re not sure whether you need a full replacement—now is the right time to get a professional assessment.

CMP Roofing can:

  • Inspect your metal roof and pinpoint leak sources
  • Determine whether repair, coating, or retrofit options are viable
  • Compare retrofit vs replacement cost and lifecycle outcomes
  • Build a plan that aligns with your operations and capital budget

To schedule a commercial metal roof assessment in Calgary or surrounding areas, visit:

For more education on leak repair, coatings, inspections, drainage, and system selection, explore our full blog at https://cmproofing.ca/blog/ and our Commercial Roofing Services overview at https://cmproofing.ca/services/.

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