How bad was the damage to the new $20 million, 130-unit multifamily property in Jacksonville, Fla.?

“The worst I’ve seen. Moisture penetrated the exterior wall system and rotted structural lumber in less than a year,” says 13-year industry veteran Darrin Sparks, a regional sales executive for Tamlyn, a building products manufacturer.

Sparks says the culprit was stucco, one of several cladding materials used in the design, along with lap siding and brick. “The other cladding materials presented no water problems,” he reports.

The stucco was made with Portland cement, augmented with polymers to mitigate brittleness. Unfortunately, the combination has very low water vapor permeability which is an essential mechanism for drying. Traditional lime-based stucco is more vapor-open, allowing trapped moisture to escape. Vapor-closed stucco was applied directly on the house wrap, a layering technique that proved disastrous in Jacksonville’s semi-tropical climate.

Countdown to Failure

“The sun comes out after an early afternoon shower and water vapor is transmitted into the wall system. Water vapor and water leakage through capillary action infiltrates the system. Without sufficient separation between the stucco and wrap, moisture has no easy escape path and access to drying air,” Sparks explains. Space between the layers, such as built-in spacers in the wrap would allow moisture to escape and air to dry. As it is, water eventually finds its way through the wrap, sheathing, and eventually to the building frame. “The damage you see in the pictures occurred in less than 12 months,” Sparks warns.

The toll was immense.

The owner was forced to rip out all stucco-clad areas down to the rotting structural timbers. Meanwhile, costly litigation commenced. The replacement cladding was a panel-and-channel fiber cement system using Nichiha 5/16ths panels. The trim channel is 3/8ths of an inch, a fit purposely spaced to let water in … and out. As an extra precaution, a high-performance house wrap was installed, ensuring sufficient air- and water-flow circulation within the wall system. The patented wrap, called TamlynWrap Drainable Housewrap, has non-compressible spacers that act as a capillary break in a pattern that channels moisture more effectively and promotes drying.

Lessons learned? At least three, Sparks says:

  1. Follow Code. “Building to code is the bare minimum and nothing to brag about,” Sparks says. Installers are expected at minimum to wrap the structure with a two-layer water-resistant barrier system, per IBC 2510.6, and complying with ASTM E2556, Type 1. “The funny thing is the Jacksonville crew thought they were doing it right,” notes Sparks. The wall assembly concealed the problem until it was far too late to correct.
  2. The Cheapest Cladding and Housewrap are the Most Expensive. Trying to shave dollars on the exterior wall assembly cost a fortune in remediation and lost business income. Why not do it right the first time?
  3. Tuck the Shower Curtain Inside the Tub. The Physics must be respected, Sparks says. The science of condensation, dew points, and relative humidity can seem complicated. Keep it simple: Manage water by providing drainage and ventilating the cladding so moisture escape can be certain.

The best ideas are the simplest, especially when it comes to water management. For example, a rain screen allows the free flow of air behind the cladding, allowing moisture to harmlessly escape and dry. Installing the right drainable house wrap manages water simply and effectively. It’s a level of cladding separation that could have saved all involved a world of grief.

And the Jacksonville apartment today? Sparks says the ordeal is over. “It’s dry, occupied, and the owner is in happily-ever-after mode.”

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