Skip to main content

2021 IECC Window Detail: CMU Wall with Stucco

Image
2021 IECC Window Detail: CMU Wall with Stucco
Courtesy Of
BSC

Notes

Window Detail 2 - CMU Wall with Stucco

  • Note: Always follow the window manufacturer’s installation guidance. Not following manufacturer guidance may void the warranty.
  • This is a “mass/storage wall” where rainwater is controlled by the stucco that is directly adhered to the CMU. This is not a “drained wall”. Any water that passes through the stucco is stored, absorbed, and redistributed within the wall assembly and then dries to the exterior or interior or both.
  • The window openings are drained to the exterior of the wall.
  • The window rough opening is flashed to the face of the CMU with a fluid-applied membrane flashing. The fluid-applied membrane flashing is applied to the rough opening inwards at least past the point where the interior air seal is located around all sides of the frame. This creates water-resistant surfaces inside the cavity between the window flanges and the interior air seal, in case any water gets behind the flanges. The window flanges (head and jambs only) are flashed to this fluid-applied membrane using a mastic flashing seal or self-adhered flashing membrane. Note the tiered precast unit at the window sill opening. This provides drainage to the exterior of the wall. The window is installed using shims just like with a wood-framed sill. The secondary seat, or backdam, of the precast sill should be located far enough to the interior to allow space between it and the window so that shims can be adjusted during installation, and to allow the interior air seal backer rod and sealant to be installed. A sill can be made of treated lumber as an alternative to the tiered precast sill. The sill should still be sloped for drainage.
  • It is vital that the mastic flashing seal at the window head and jamb flanges is carefully detailed. There is no mastic flashing seal over the window flange at the sill. This is to allow any water that may get past the head or jamb flanges to drain back out.
  • Backer rod for the interior air sealant should be installed after the window is installed, leveled, and shimmed. Use correctly sized backer rod.
Window Drawing image + notes (png) (688.12 KB)
Window Drawing + notes (landscape) (574.78 KB)
Window Drawing + notes (portrait pdf) (576.81 KB)

Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.