What is the loading gap

Bed joints are horizontal joints of ceramic brick blocks. The loading joint is formed by placing the bricks in a spreading mortar layer that forms a bed gap in the masonry. The thickness of the bed joint for sand-lime bricks results from the 250 mm building height used, specifically from the height of the bricks.  The adhesive or mortar must be applied to fill the entire load gap.  The ideal thickness of the joint is 12 mm. The gap must not be too thick or too thin. 

When the loading joints are different in thickness, the strength of the masonry is reduced, unevenly cracked areas are created which are consequently the cause of expansion joints.