Why Is My Commercial Roof Leaking?

May 14, 2019

Leaks are the most common issue reported by facilities professionals. They are especially problematic on roofs with heavy foot traffic and numerous penetrations. While no roof system is immune to the occasional roof leak, being mindful of the most common causes can help with prevention.

1. Lack of Maintenance

Regular roof maintenance is the best way to avoid roof leaks; it catches problems before they exacerbate. For example, the life of caulking is only six to eight years. A regular roof inspection will examine the condition of caulking and sealants for counterflashings and terminations and replace or seal if necessary. Pitch pans sealant that dries out, shrinks, cracks, and pulls away from the sides is another potential leak source. Without an inspection to detect these failing sealants, you risk water infiltration.

Additionally, the root system of plants will quickly destroy a roof membrane and the insulation beneath. This not only obstructs drainage but also creates a path for water to enter the building. General preventive maintenance usually includes cleaning drains, replacing sealants and making repairs at the earliest onset of deterioration or damage.

2. Damage by Other Trades

Mechanical systems, HVAC equipment, grease vents, and process piping need regular servicing and turn the roof into a work platform. When sharp tools are dropped, HVAC panels slice through single-ply membrane, or dropped screws and nails are walked on, destruction is inevitable. If left unattended, water will infiltrate the roof system through the puncture, saturate the insulation, and possibly even corrode a metal roof deck.

3. Weather

During high winds, rooftop unit hoods, cracked skylights, tree limbs, debris, and obsolete equipment is forced from its location and pushed across the roof surface causing punctures, tears, and abrasions to the membrane. Hail can also cause similar damage.

Spring and summer storms aren’t the only destructive weather. If drainage paths freeze in winter, ice damming along the perimeter of the roof is likely and may also cause leaks. Temperature fluctuations with the seasons cause expansion and contraction. Flashings are often the first things to fail because they’re pulling so tightly. It’s not uncommon to discover leaks and wet insulation in the spring.

4. Poor Installation/Workmanship

A roofing contractor that isn’t a certified applicator or who cuts corners so he can provide a low bid will deliver poor workmanship that can result in unexpected leaks from your new roof. The manufacturer and contractor should perform in-progress installation inspections to ensure that compatible materials and correct application methods were used.

5. Roof Materials That Have Exceeded Their Service Life

An older roof with membrane at the end of (or has exceeded) its intended life cycle, is not nearly as flexible as a newer roof and cannot perform under extreme conditions and drastic temperature changes, causing large splits or tears and damage to flashings, all of which lead to leaks. As your roof (or components of it like the caulking we mentioned earlier) ages, plan for more frequent inspections and maintenance. Schedule that coating, recover, or roofing project before the leaks are so bad you’re forced into action.

Remember, the best way to investigate and determine the cause of water infiltration is always a leak evaluation. Many roofing professionals follow ASTM D7053-07 Standard Guide for Determining and Evaluating Causes of Water Leakage of Low-Sloped Roofs.

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