Plan Ahead for the Hidden Sources of Moisture on Your New Commercial Roof

man working on low slope roof

Moisture generated from inside commercial buildings can greatly impact the longevity of a low-slope roofing system. And while today’s manufacturers are producing the most durable low-slope materials to date, it's still the responsibility of the building owner to make sure proper ventilation systems and maintenance protocols are in place to protect the roof.

We'll outline three environments where internally-generated moisture can occur and how to combat them.

1. Moisture generated in small commercial building settings

A certain amount of moisture is generated in every office space, retail setting, and production facility. And as we all remember from middle school science classes, warm air rises. Warm air carries moisture, and in commercial settings, the air causes condensation to build between the roof’s membrane and its insulation.

What industry experts recommend:

  • Do everything in your power to prevent condensation in the first place. When installing your roof, request two layers of insulation with staggered roof joints, as this mitigates the movement of hot, heavy air to the underside of the roof membrane. Commercial roofs are quite large, so attempting to dry them out during clear, warm days is an arduous effort.

  • If there is only a single layer of insulation, consider installing cover boards like high-density Polyiso boards. Use staggered joints.

  • Be extremely cautious about what adhesive is being used to install the roof membrane. Some are water-based and can turn back into water when exposed to high amounts of moisture. If at all possible, choose an adhesive specifically stating its tolerance for humid environments.

Keep reading about commercial roofs:

2. Moisture generated in large commercial building settings

Hidden sources of commercial roof leaks

Larger commercial buildings, such as laundries and hotels with swimming pools, generate a great deal of internal moisture.

With such cases, the building should have an adequate ventilation system outfitted to handle such large amounts of moisture. Additionally, the whole building should be constructed and designed so that excessive condensation build-up does not happen. For these cases, a consultant who specializes in large commercial spaces should be involved.

Some consultants favor the use of air and vapor barriers. In order for these barriers to function properly, they need to be applied with the utmost care and without damage to their structural integrity.

By placing an air and vapor barrier lower in the roof system, it prevents excessive moisture from reaching the roof membrane, while also preventing any leaks from above from going any further.

Learn more about roof ventilation:

3. Moisture generated through construction

Commercial roof leaks

A lot of construction practices bring added moisture into a commercial building. Small improvements, like interior painting or new drywall installation, bring a small amount of added moisture into the building. However, some construction projects bring much more moisture into the building over a longer period of time.

The biggest culprit of this is concrete slab floors. Concrete slab floors and concrete roof decks contain and release a measurable amount of water even after curing is complete. Experts disagree about the best methods for combating concrete-released water vapor, but it’s important to remember the following:

  • Little correlation exists between the time it takes concrete to cure and the amount of water remaining. Even following the recommended 30-day minimum is not effective in completely eliminating moisture release.

  • Newly poured concrete is not as dry as it appears. It takes a significant amount of time for water to diffuse from four inches of concrete. Even the old “plastic sheet test” is not as reliable as we all once thought. The test involved taping a plastic sheet to the concrete and seeing if any moisture appeared underneath it over time.

  • Concrete decks should be covered with a vapor barrier. They must be installed carefully and correctly to ensure they capture moisture. Remember: Nearly all commercial roof membranes are impermeable; once moisture gets into the roofing system, it will not have a way to escape.

  • Always, always make sure professional commercial contractors with experience mitigating moisture problems are involved in the construction and renovation process. Structural engineers and concrete suppliers are great to involve.

The majority of commercial roofing systems are installed correctly and perform adequately for a number of years. If the roof does suffer from premature problems, it could be from improper installation practices or excessive moisture. If your roof is suffering from any serious problem, contact a commercial roofing contractor immediately.

Find a commercial roofing contractor

Keep reading about how to find the right commercial contractor: