Is glazed brick safe to use in areas that experience freeze-thaw cycling?
Glazed brick has been used on many buildings located in freeze-thaw environments. In some buildings, glazed brick have failed, resulting in spalling of the units' faces. Failure often occurs in solid masonry walls with excessive water penetration. Manufacturers typically recommend that glazed brick be used only in cavity or veneer-wall construction where there is an air space behind the glazed brick wythe.
This solid masonry parapet failed because it did not have a drainage cavity and there was ineffective flashing underneath the cap stones.Photo by Norbert Krogstad

The glaze on the exterior face of the brick restricts moisture evaporation. A vented air cavity helps dissipate moisture. Glazed brick units should meet the requirements of ASTM C 126 "Specification for Ceramic Glazed Structural Clay Facing Tile, Facing Brick and Solid Masonry Units." For exterior use, many experts recommend that the glazed bricks' maximum moisture absorption be 7% and the saturation coefficient be no greater than 0.78.As in any masonry wall, flashings, copings and sills should be carefully designed to prevent water from penetrating the walls. It is also important to tool concave mortar joints in a glazed brick wall to provide proper compaction. Proper tooling, along with full head and bed joints, will help control water penetration through the masonry's face. If water penetration is kept to a minimum and there's a properly vented cavity behind the face of the glazed brick, the wall system should be durable in freeze-thaw environments.