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Mortar cracks that continue through blocks

Mortar cracks that continue through blocks

Mortar cracks that continue through blocks

We have an exterior wall made of three layers of bricks facing east. On the outside is a 4” face brick, in the middle is a 4” common brick, and on the inside is a 4” structural glazed tile. The building was constructed a few decades ago and they used large W-Sections for the columns. The columns are placed every 21’ and they are between the common brick and the structural glazed tile. The problem we have is that there are cracks in the mortar along the north and south sides of the columns. The interesting thing is that the cracks is down a vertical mortar line and does not jog over to the next mortar line when it hits one of the tiles. Instead it breaks the tiles in half and matches back up with the same mortar line on the other side of the tile.

The question we have is what could be causing the tiles to be cracking?  We figure if it is the wall pulling away from the column it would follow the mortar lines, but since it does not we are wondering what kind of forces could be applied to the column to shear the tiles in half. The tiles are 4”Hx4”Dx8”L and they are hollow making them about 1” thick. The beams above the columns are composite sections of concrete and W-Sections. If anyone has any suggestions of what we could look into or if any more information is needed. Please let me know.

Thank you all for your time.

RE: Mortar cracks that continue through blocks

The type of cracking you describe is not uncommon.  In my years with the Brick Institute of America I saw such cracking often.  It is likely caused by differential movement between the columns and the walls.  To avoid this, a control joint is typically used in modern construction, but that was not the case with older buildings with three-wythe masonry infill walls such as yours.  The nature of the crack propagating thru the tile units versus around them could be related to the rate at which the crack propagated, but again, it is not uncommon to see either of these two scenarios.

For remediation, provide a control joint to allow unrestricted movements of the building frame relative to the masonry wall, but make sure you provide adequate metal masonry ties between the masonry and the frame to laterally support the masonry wall.

RE: Mortar cracks that continue through blocks

I agree with hoolie that it is a differential movement problem.  When masonry cracks through the section without following the mortar joints, it is a result of overstress, not just shrinkage.  In this case, either your columns or your wall have settled slightly, one relative to the other.  This causes shear stress in the structural tile or any other masonry attached to the column.  Keep in mind that it only requires a very small amount of strain to cause these cracks over short distances in masonry.

Isolation is the solution.

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