Alternately, cap nails can be used as spacers between the water control layer and the rigid insulation. If the water control layer (drainage plane) is behind the insulation and over the exterior sheathing, the drainage space can be achieved by installing a layer of textured house wrap over a water control membrane.Provide a drainage space in front of the water control layer:.Or, if the face of the rigid insulation is to be the water control layer, tape the joints with acrylic sheathing tape or self-adhered membrane (which is recommended at the inside and outside corners for better adhesion) and flash the windows, doors, and penetrations to the face of the insulation. IRC 2018 requires the water control layer to be equivalent to two layers of Grade D paper. Install a water control layer (building wrap, self-adhered or fluid-applied membrane) over the face of the exterior sheathing and flash all windows, doors, and penetrations to that layer.Typically this will be behind the insulation and over the exterior sheathing, but the face of the rigid insulation may also serve as the wall’s water control layer/drainage plane if the joints are taped. Determine the location of the wall’s water control layer (the drainage plane).How to Install Stucco over Continuous Rigid Insulation In this case, the second layer of sheathing must be protected from decay by installing a water control membrane over it with a drainage gap. Where more than 1.5 inches of continuous exterior rigid foam insulation is installed, additional structural support such as a second layer of structural sheathing (plywood or OSB) may need to be installed over the rigid foam. The following guidance is for installations where 1.5 inches or less of continuous exterior rigid foam insulation is installed under the stucco cladding. That said, there are material (and perhaps also labor) cost savings associated with using the face of the insulation as the water control layer (a separate membrane is no longer required). When the face of the insulation becomes the water control layer, window and door flashing details must be adjusted accordingly and a different installation sequence must be followed. Indeed, keeping the water control layer at the face of the exterior sheathing means that standard window and door flashing details (and standard installation sequencing) are maintained – windows, doors, and other penetrations are flashed to the water control layer at the face of the sheathing regardless of whether continuous insulation is used or not. With respect to the location of the drainage plane, either over the face of the sheathing (behind the insulation) or at the face of the insulation, the former is far more common than the latter. Windows are flashed to the drainage plane (not seen), which is behind the insulation. Figure 1. Expanded polystyrene insulation is installed with joints taped and lath attached in preparation for the application of stucco. Coordination between the designer or builder and installing subcontractor is required. After the insulation is installed, the stucco cladding may be installed per typical manufacturer requirements. This involves determining the location of the wall’s water control layer (typically behind the insulation over the exterior sheathing), providing a drainage gap in front of the water control layer, and flashing all windows, doors, and other penetrations to the water control layer prior to installing the insulation. Installing stucco cladding over rigid foam insulation requires additional preparation to ensure proper water management as well as a sound substrate for the stucco. For this reason, it is essential that proper drainage is provided behind cladding materials such as stucco. With increased efficiency and comfort, however, also comes an increase in the risk of water-related building failures (such as mold, rot, and odors) because the exterior insulation reduces the energy flow through the wall, which also reduces its capacity to dry. (Stucco is the subject of this guide, but please note that adhered stone and tile follow the same principles). In response to more demanding energy codes, and as occupants and home owners press for more energy-efficient, thermally comfortable, and quiet houses, builders and designers are increasingly considering continuous rigid foam exterior insulation, even in warmer climates (zones 1-3), and with cladding types more common to those warmer climates.
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