Common Roof Problems

Understanding common commercial roofing problems helps building owners recognize early warning signs and take prompt corrective action. Many roof issues develop gradually, and early intervention typically costs far less than repairing the consequences of advanced deterioration. Knowing what problems to watch for supports effective maintenance and helps extend roof service life.

Roofing membranes can shrink over time, particularly certain EPDM formulations and some older PVC products. Shrinkage creates stress within the membrane, pulling it away from secure attachment points and potentially tearing seams. Signs of membrane shrinkage include visible rippling or tenting of the membrane, separation at perimeter edges or penetrations, and stress concentrations at fasteners or attachment points.

Shrinkage often accelerates when roofs experience significant temperature cycling. The expansion and contraction associated with temperature changes, combined with gradual material shrinkage, creates cumulative stress. Older roofs and those manufactured before improvements in membrane formulations show higher susceptibility to shrinkage problems.

Addressing shrinkage typically involves relieving stress points through strategic cuts or by installing stress relief patches. Perimeter edges may require new termination bars installed closer to the current membrane edge. Severe shrinkage sometimes necessitates membrane replacement if stress relief measures are insufficient or if the shrinkage has caused extensive damage.

Flashing assemblies represent the most common location for roof leaks. These vulnerable areas where the roof membrane transitions to walls, penetrations, or other building components experience more stress and movement than the main roof field. Flashing failures manifest in various ways depending on the specific detail and materials involved.

Metal counter-flashing that protects wall-to-roof transitions can pull loose from wall anchorage, separate from base flashings, or develop holes from corrosion. Missing or displaced flashing provides direct pathways for water infiltration. Sealants used in flashing assemblies deteriorate over time, becoming brittle and shrinking away from substrates. Failed sealants allow water to migrate behind flashing and into building assemblies.

Pipe and equipment support penetrations concentrate stress and movement in small areas. The repeated thermal expansion and contraction of metal pipes and supports can fatigue flashing materials. HVAC equipment vibration can loosen flashing attachments over time. These penetrations require periodic inspection and maintenance to prevent failure.

Proper flashing repair requires understanding the specific assembly details and using appropriate materials and techniques. Simple sealant application rarely provides adequate long-term solutions. Effective repairs typically involve removing deteriorated materials, preparing substrates properly, and installing new flashing following manufacturer specifications.

Inadequate drainage accelerates roof deterioration and increases leak risk. Water that doesn't drain within 48 hours after precipitation constitutes ponding, which concentrates UV exposure, promotes algae growth, and stresses membrane seams. Persistent ponding shortens membrane life and increases the likelihood of leaks as the membrane deteriorates in constantly wet conditions.

Blocked drains are among the most common and preventable drainage problems. Leaves, debris, and sediment accumulate around drains, impeding water flow. Completely blocked drains force water to find alternative paths, often resulting in perimeter overflow or infiltration through vulnerable points. Regular drain cleaning as part of routine maintenance prevents this common problem.

Roof slope inadequacies sometimes emerge over time as buildings settle, decks deflect, or insulation compresses. Areas that drained properly when new may develop ponding as conditions change. Structural changes from additions or modifications can alter drainage patterns. Addressing slope-related ponding typically requires adding tapered insulation or improving drainage capacity.

Inadequate drainage system capacity can overwhelm roofs during intense rainfall. Scuppers or drains sized for typical weather may prove insufficient during extreme precipitation events. Climate patterns characterized by intense storms may require drainage system upgrades beyond original design parameters.

Commercial roofs expand and contract with temperature changes. A dark-colored roof can experience surface temperatures exceeding 160°F on summer days and drop well below freezing in winter. This thermal cycling creates movement that roofing systems must accommodate. Problems develop when systems cannot adequately handle this movement.

Membrane splitting can occur when thermal contraction exceeds material flexibility or when attachment restricts necessary movement. These stress-related splits typically appear perpendicular to the direction of restriction. Fastener pull-through develops when repeated expansion and contraction loosens fastener attachments, allowing the membrane to pull away from deck anchorage.

Adequate expansion joints in roof systems help accommodate building movement and reduce stress on roofing materials. Buildings longer than 200 feet or with complex configurations typically require expansion joints to isolate different roof sections. Missing or improperly maintained expansion joints can result in system distress as the building structure moves beneath the roofing.

Wet insulation beneath the roof membrane compromises thermal performance and accelerates system deterioration. Moisture can enter roof assemblies from leaks from above, from condensation when warm interior air contacts cold roof decks, or from construction moisture that was never properly dried. Wet insulation is difficult to detect without specialized equipment but indicates serious problems requiring attention.

Infrared thermography surveys can identify wet insulation areas by detecting temperature differences between dry and wet sections. Once moisture infiltration is confirmed, determining its source and extent guides repair strategies. Small isolated wet areas sometimes warrant localized repair, while widespread moisture infiltration typically requires more extensive remediation or replacement.

Trapped moisture can cause additional problems beyond reduced insulation value. It can rust steel decks, rot wood decks, freeze and damage materials in winter, and promote mold growth. Addressing moisture infiltration promptly limits secondary damage and prevents more expensive problems.

Algae, moss, and vegetation growth on roofs indicate excessive moisture and can accelerate deterioration. While these growths may seem primarily aesthetic concerns, they retain moisture against the roof surface, block drainage paths, and can penetrate membrane seams. Tree roots from seeds deposited by birds can cause surprising damage, even penetrating some roof membranes.

Preventing biological growth requires good drainage, adequate sunlight exposure, and regular cleaning. Removing nearby tree branches that shade the roof and deposit debris helps minimize growth conditions. Periodic roof cleaning removes accumulated organic matter before significant growth establishes.

Chemical treatments can control existing growth, but physical removal is often necessary for heavy accumulations. Preventive treatments reduce future growth but require periodic reapplication. Addressing the underlying moisture conditions that support growth provides the most effective long-term solution.

Roof traffic, falling objects, wind-blown debris, and equipment installation or maintenance activities can physically damage roof membranes. Punctures allow immediate water infiltration and should receive prompt repair. Even small punctures can expand over time as thermal cycling and wind loads stress damaged areas.

Establishing protocols for roof access helps minimize traffic-related damage. Designated walkway pads protect high-traffic routes to frequently serviced equipment. Requiring that all roof work be performed by trained personnel familiar with roof system vulnerabilities reduces accidental damage. Prompt inspection after known roof access or nearby tree work helps identify damage before leaks develop.