If you manage a building, a leak is the last thing you want to see. It is stressful, it interrupts tenants, and it can get expensive fast. In this guide we explain the common causes of commercial roof leaks in plain language and show you how to prevent them. At Weather Shield Roofing Systems, we have helped businesses protect their buildings for over 40 years, so we know where leaks start and how to stop them early. 

What parts of a commercial roof usually leak?

Most flat or low-slope roofs fall into one of these membrane systems: TPO, EPDM rubber, PVC, modified bitumen, or built-up. Whether your roof is new or older, leaks almost always trace back to five areas: 

1. The field of the roof, the wide open membrane in the middle 
2. Seams, where two sheets or panels meet 
3. The perimeter and edges, including coping, gutters, and parapet details 
4. Drainage, such as internal drains, scuppers, and gutters 
5. Penetrations and flashings, like HVAC curbs, vent stacks, and skylights 

Let’s walk each one, including simple prevention tips you can put in place right away. 

How does the “field” of the roof get holes or weak spots?

The field is the main roof surface. It can leak when it is punctured or when it wears thin with age. 

Typical causes:

• Windblown debris like screws, nails, or sharp trash 

• Tree branches or tools dropped during service work 

• Heavy foot traffic without walkway pads 

• Long-term wear that thins the membrane 

• Ponding water that speeds up aging 

Quick fixes and prevention:

• Keep the roof clean. A quarterly walk-through to remove debris is cheap roof damage prevention. 

• Add walkway pads to high-traffic paths to mechanical units. 

• After storms, schedule a quick roof inspection to catch new punctures. 

• If your membrane is older and shows bare or thin spots, plan targeted repairs or a life-extension coating as part of your roof maintenance program. 

Why do seams open up on flat roofs and metal roofs?

Seams are where materials join, so they are naturally vulnerable. On TPO and PVC roofs, seams are heat welded. On EPDM rubber, seams are glued or taped. Over time, sun and weather can weaken these bonds. 

What usually goes wrong:

• UV exposure dries out adhesives on EPDM seams 

• Poor welds on TPO or PVC that were never bonded well from the start 

• Thermal movement and building movement that stress the joint 

Metal roofs have seam risks too–overlapped panels rely on sealants and fasteners. Hot and cold cycles cause expansion and contraction. Fasteners can back out, and seals can crack, letting water travel under the laps. 

Prevention you can use:

• Have a roofer probe-test seams during every roof inspection. Re-weld or re-tape weak spots before water finds them. 

• On metal, tighten or replace loose fasteners and renew seam sealant as part of routine roof care. 

• Limit foot traffic across seams and set rules for service contractors so tools do not damage joint lines. 

What edge and perimeter issues lead to leaks?

Perimeters take a beating from wind, ice, and temperature swings. On EPDM roofs, the membrane can shrink over time, pulling at the edges. On many systems, coping metal and edge terminations can loosen or open small gaps. 

Common problems: 

• EPDM shrinkage that tears or pulls the membrane back from the edge 

• Loose or missing termination bars and coping joints 

• Ice buildup and icicles that stress edges or pry materials apart 

• Clogged gutters that fill and backflow into the building 

Prevention tips that work: 

• Inspect edge metal and term bars each spring and fall. Tighten, re-seal, and replace as needed. 

• Keep gutters and scuppers clean. Schedule seasonal cleaning to prevent backups. 

• Watch for ice. If you have chronic ice at the eaves, consider heat cable or insulation improvements to reduce freeze-thaw stress. 

How do drainage problems turn into interior leaks?

A roof is a giant rain collector. If water cannot reach the drains, it will find another path, often through your building. 

What to watch:

• Drains, rings, and strainers broken or missing 

• Debris like leaves, dirt, or roofing granules blocking flow 

• Internal drain piping that freezes, expands, and cracks 

• Low spots that cause ponding water for more than 48 hours 

Smart steps: 

• Clean drains and gutters at least twice a year, and after heavy leaf drop. 

• Make sure every drain has a basket or strainer. Replace brittle parts on older systems. 

• Water test suspect drains during an inspection so you know they flow freely. 

• If the deck is settling and creating ponds, ask about adding tapered insulation during your next capital project to improve drainage and protect roof lifespan. 

Why are rooftop units and penetrations the number one leak source? 

Every penetration is a hole through the roof. HVAC curbs, vent stacks, skylights, satellite mounts, and pitch pans add corners and seams. Flashings around these details age faster than the flat field. 

Typical flashing failures:

• Dried-out sealant and cracked corners 

• Flashing boots that split or slip 

• Loose counterflashing at walls or curbs 

• Damage from service contractors pulling wires or moving equipment 

How to stay ahead: 

• Reinforce corners with extra membrane plies at installation or during repairs. 

• Use pre-molded boots where possible. They last longer than field-fabricated details. 

• Coordinate with HVAC and other trades. Require them to call your roofer before cutting or removing flashings. 

• During routine roof inspections, spend extra time at every curb and pipe. These spots deliver the biggest leak reduction for the least cost. 

What simple maintenance plan prevents most leaks?

Proactive roof maintenance is the best way to protect your roof investment and lower emergency roof repair costs. 

A practical schedule: 

• Inspect in spring and fall, and after severe storms. 

• Clean drains, gutters, and rooftops during each visit. 

• Probe seams, check edges, and re-seal flashing corners. 

• Document with photos and a prioritized action list so you can budget repairs. 

At Weather Shield, our Max Life Roof Care program is built around these steps. It turns small fixes into big roof cost savings by catching issues early and extending roof lifespan. 

How do I decide between repair, restoration, or replacement?

It depends on the roof’s condition and your goals. 

• Repair if leaks are isolated, the membrane is still thick and flexible, and the insulation is dry. 

• Restoration if the roof is mostly sound but aging. Coatings or targeted re-surfacing can add years and improve energy performance. 

• Replacement if seams and flashings are failing everywhere, the membrane is brittle, or moisture has spread through the insulation. In some cases, a recover system can control cost while delivering long-term performance. 

A clear roof inspection with moisture readings, photos, and a repair budget will point you in the right direction. 

What can my team do right now to reduce leaks?

• Control access. Keep a roof log for anyone going up. 

• Use walkway pads to protect high-traffic routes. 

• Keep trees trimmed away from the roof edge. 

• After wind or hail, schedule a roof inspection even if you do not see leaks yet. 

• Add a recurring reminder to clear drains in spring and fall. 

Quick recap, where do leaks start most often?

• The field, from punctures and wear 

• Seams, where materials meet 

• Perimeters and edges, from movement and ice 

• Drainage, when water backs up 

• Penetrations and flashings, around equipment and pipes 

Finding and fixing issues in these five areas is the fastest path to roof leak prevention and better roof investment protection. 

Weather Shield Roofing Systems is committed to transparent, cost-efficient solutions that keep your business dry and running. If you want help building a simple maintenance plan or need an honest roof inspection, we are here to help. Contact us today. 

Kyle Bruinsma

Account Executive

Since 2019, Kyle Bruinsma has delivered high-quality, cost-effective commercial roofing solutions at Weather Shield Roofing Systems. As both a roofing professional and commercial property investor, he brings a unique perspective to each project—treating every building like his own. Kyle values the strong team culture at Weather Shield, where everyone works together to keep customers dry.