9.15.4.9. Crack Control Joints

 9.15.4.9. Crack Control Joints

This Article sets minimum distances for the location of joints in foundation walls designed to reduce #cracks so that the entry of soil drainage #water and #moisture can be minimized.

Both cast-in-place #concrete and concrete block shrink over time as a result of curing and drying. To control #shrinkage cracking, concrete block masonry units are either steam cured or autoclaved by the producer, and are required to satisfy permissible limits on linear drying shrinkage. Even so, some shrinkage may be expected for both cast-in-place concrete and concrete masonry #foundation walls.

Crack control joints may be necessary to accommodate this shrinkage. These joints are designed to move apart slightly as the wall shrinks, while maintaining a watertight surface. These are required to be installed not more than 15 m (45 ft.) apart when the foundation walls are longer than 25 m (75 ft.). Figure 9.15.-17 illustrates the requirements for crack control joints in foundations and two approaches for sealing the joints.

Where possible, crack control joints should be placed adjacent to a #window opening, where the concentration of tensile stresses encourages shrinkage cracks to occur.

Quoted from Illustrated Users' Guide - NBC2015

#crackcontroljoints #foundationwall #castinplaceconcrete #tensilestress