AppNote AN12

printable version

RE: Installation of FMCA and TC series backboxes in concrete on grade

FMCA and TC series backboxes can be relied upon to provide long-term service when installed on grade, provided certain precautions are taken in the planning and execution of the installation.

The FMCA and TC series backboxes are coated with a gray ceramic/plastic urethane coating that has been tested according to ASTMB117 (Test#2167, sample B) on a steel panel subjected to 2000 hours of salt fog, and passed with no degradation of the finish. This finish provides corrosion resistance superior to that found on galvanized boxes used in similar concrete or masonry applications.

When backboxes are installed on grade, we recommend they be completely encased in concrete. This can be done by excavating the fill (gravel, dirt, etc.) below and around the backbox to a minimum of six inches .

The offset in the pour provides a uniform thickness of concrete below the backbox to prevent hydrostatic flow of ground water seepage into it, and keeps the backbox from direct contact with the grade. Proper site grading is prerequisite.

The installation instructions furnished with each backbox describe an additional pitch coating that can be applied to the exterior of the backbox where further corrosion protection is warranted. Use of FMCA and TC series backboxes is generally not recommended below grade or in areas below sea level, where high risk of severe corrosion is present.

To ensure a successful installation, please consult the appropriate TechNote for each product referenced below.