Understanding A Wet Roof Deck

Wet roof decks simply can’t be ignored. Recovering a wet roof deck won’t make the problem go away. That’s because recovering a roof deck will likely only cause the roof to blister, or cause other serious problems that won’t be covered by the manufacturer’s warranty.

Here’s how to tackle a wet roof deck the right way. First, identify wet areas in the roof. To do so, one of three types of moisture surveys should be completed: infrared, nuclear or capacitance. None of these actually measure moisture. Instead, they measure the effect moisture has within the roofing materials.

For the best results, match the type of moisture scan with your roof because each moisture scan works differently. Infrared surveys measure the heat retained or lost in insulation that has become damp. Ballasted roofs aren’t a good candidate for infrared surveys because the rock itself retains a lot of heat, giving potentially false readings. Nuclear moisture surveys measure hydrogen atoms in the roof, meaning that any membrane with a large hydrogen chemical component will send a positive reading. Water is a good conductor of electricity, and capacitance surveys measure electricity traveling through the roofing material. This survey won’t work on a roof with wet or ponded areas, and EPDM roofs may require modified instruments.

The amount of moisture found in the roof, if any, may dictate the choice of whether to recover or replace. The more areas of moisture found, the more expensive it will be to replace those areas. If you have 100,000 square feet of roof and four 8-by-10-foot areas are wet, replacing those sections makes sense. But if 30 percent of your roof is wet and it’s scattered throughout the roof, the labor to replace all of those sections probably equals the cost of just tearing off the entire roof.

But what if the roof is leaking just after a recent replacement? It’s not that far-fetched. Due to poor design or installation, many roofs experience water leakage soon after construction. In many instances, water leakage through a roof membrane can go unnoticed because a vapor retarder at the bottom of the roof system captures the water. The captured water absorbs into the insulation, significantly decreasing the thermal value of the insulation and causing premature deterioration of the roof system.

A properly prepared and implemented design can prevent water from migrating into the roof. Generally, the membrane in the roof’s field does not allow bulk water leakage. Most leaks through a system arise from unreliable detailing. For example, in most instances, roof terminations consist of surface-mounted conditions (exposed termination bars or metal flashing) or reglet-set flashing (a small cut in a wall system to insert the metal flashing).

The team at RAMCON is uniquely qualified to identify and address saturated roofing systems and wet roof decks. We’ll perform moisture surveys and noninvasive testing that will determine whether or not repairing or replacing a roof is the most cost efficient solution.