FMA/AAMA 200-09 Addresses Proper Installation of Windows in Masonry WallsMarch 31, 2010
The second installation standard practice published by AAMA in collaboration with the Fenestration Manufacturers Association (FMA), FMA/AAMA 200-09, Standard Practice for the Installation of Windows with Frontal Flanges for Surface Barrier Masonry Construction for Extreme Wind/Water Conditions, now joins FMA/AAMA 100-07, Standard Practice for the Installation of Windows with Mounting Flanges for Extreme Wind/Water Conditions. These standard practices provide industry best-practices for preventing liquid water from entering through a window – wall interface under extreme wind/water conditions. The focus is on the installation of frontal-flanged windows into low-rise masonry or concrete buildings (no more than three stories in height). The standard practice does not address mulled window assemblies or replacement systems. Installation into wood-frame construction, such as often used on second and third stories of a masonry building, are covered in FMA/AAMA 100-07.
The FMA/AAMA 200-09 standard practice is the first ever publish standard to address the unique surface barrier masonry wall construction, commonly found in the southeastern U.S. A key feature of this standard practice is the specification of a water resistant coating, or “Liquid Applied Flashing”, applied around the rough opening return and entire sill area. This treatment is designed to prevent water that either collects or is absorbed into the wall from entering the building interior through the window opening, making the erroneous ‘appearance’ of a leak at the window or window/wall interface. This water will be directed away from the window/wall interface to exit at the bottom of the CMU wall or other flashing termination.
The standard provides details for both a “barrier installation,” in which there is a full perimeter seal at the exterior interface between the window and the wall cavity (under the flange), and a “drainage installation,” in which a discontinuous seal at the exterior sill interface allows drainage from sill pan flashing systems allows liquid water to escape.
In general, barrier construction establishes an air/water seal around the exterior perimeter of the window. It is often inadequate to maintain a continuous water barrier over the entire building envelope in climates with frequent and/or heavy rainfall. In addition, once water breaches the barrier and is absorbed by the construction material, the barrier inhibits the ability for the wall to dry out rapidly.
A water-managed/drainage plane approach allows water to get past the exterior cladding, where it encounters a secondary water resistant barrier that drains down the cavity where it is flashed to the exterior. This approach is better suited for areas that experience heavy rain. Such drainage installations must establish a robust air/water seal around the interior perimeter of the window/wall cavity interface.
The installation procedure outlined in the FMA/AAMA 200-09 standard covers four phases:
- Pre-Installation Inspection and Preparation (which includes treating the masonry adjacent to the opening with a water resistant coating)
- Installation of Buck, Receptor or Similar Mounting Device, including illustrations of proper anchorage and sealing techniques
- Installation Procedures, including details of proper interior and exterior sealing for both the surface barrier and drainage installation methods
- Post-Installation Procedures, consisting of final inspections and testing for proper operation of movable sash, hardware and weep holes
The standard practice features 26 illustrations of the installation steps, providing a “user friendly” format to provide guidance for field installations. Appendices illustrate recommended head, jamb and sill details, and list the typical responsibilities of the general contractor/design professional, the installation contractor and the window manufacturer.
The new installation standard is available in AAMA's Online Publication Store.