There is an increased risk of cracking at changes in thickness loading and height.
Movement joints in concrete block walls.
Change in wall height or thickness see figure 1 figure 2 change of loading see figure 3 abutments of walls and columns see figure 4 junctions of dissimiliar materials see figure 5.
Greater distances between movement joints 9 m and sometimes longer are possible in aggregate concrete blockwork walls depending on the location and block type.
The added resistance to movement afforded by the nearby intersecting wall at the corner causes cracking to appear in a stair step form following the mortar joints in the concrete block or brick whereas the same settlement or heaving forces might have caused more nearly vertical cracks if they had occurred closer to the center of the wall.
At corners consideration should be given to the effect of restraint and may require the first movement joint being positioned closer to the corner than the general rule of thumb suggests.
An expansion joint in brickwork and blockwork is a means of solving potential problems caused by movement.
Maximum horizontal spacing of control joints in unreinforced concrete masonry walls should be approximately 32 feet but a length spacing to height of wall ratio is a better measure.
The first movement joint should not be more than 3m.
Block manufacturers should be consulted for guidance.
This movement could be a result of thermal expansion moisture movement creep and structural loading or the effect of chemical changes.
In our concrete block wall crack photo shown below you can see both step cracks at the wall corner and a horizontal crack at the bottom of the upper 1 3 of.
Lead to a requirement for movement joints in end walls particularly with concrete block brick masonry.
In practice providing that the length of an end wall between returns is not greater than the normal spacing of movement joints for the masonry material it should perform satisfactorily even when the rst.
Ultralite insulite and dense concrete block walls should be divided into approximately 8 12m long panels for internal.
An information series from the national authority on concrete masonry technology control joints for concrete masonry walls empirical method tek 10 2c movement control 2010 introduction concrete masonry is a popular construction material because its inherent attributes satisfy the diverse needs of both exterior and interior walls.
Movement joints such as control joints are one method used to relieve horizontal tensile stresses due to shrinkage of the concrete masonry units mortar and when used grout.
They are essentially vertical planes of weakness built into the wall to reduce restraint and permit longitudinal movement due to anticipated shrinkage and are located where stress concentrations may occur.
They are placed in concrete masonry walls to prevent cracking.
Movement control aggregate concrete blocks position of movement joints consideration for the location of movement joints should be given at.
Each panel should be separated by a suitable vertical movement joint placed in an unobtrusive location note.
