Cordyline Aspire Limited
Consulting Civil & Structural Engineers
 
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Common Brickwork Defects 
 
 
Cracking can occur in brickwork for a number of reasons:-

Ground movement leading to foundation failure

Rapid change in load leading to disproportionate settlement

Mobile ground water undermining foundations

Thermal movement

Wall rotation due to lateral instability

Excessive lateral loads on walls

Accident

 
 
 
 
 
Brickwork Cracks
 
Diagonal Cracks
Cracks that are the result of ground movement tend to be diagonal in nature with vertical cracks showing as hairline at the point of rotation and wider further away.  Examination of the variation in crack width will reveal which part of a wall has dropped, or, conversely, risen. Similarly examination of junctions with cross walls will often reveal an opening of a vertical crack showing the direction of movement both lateral and vertical.

Similar cracking can be exhibited in older properties with basements in which a timber wall plate carrying the ground floor has rotted thus allowing localised compression below heavily loaded sections of wall.

Vertical Cracks
Vertical cracks close to external corners can be the result of excess restraint in cavity construction or the result of thermal movement.  In theory the movements causing these cracks is fully reversible such that the cracks should close during warmer weather and open once again when cooler.  In practice small pieces of debris lodge in the crack restricting the degree of closure.  The effect is that cracks widen over time and then stabilize with little visible movement taking place.

Along extensive brickwork elevations cracks will be seen at approximately 12 metre centres (particularly if exposed to full sunlight for much of the day).  This is the natural limit to which brickwork can withstand thermal movement.  In new construction joints are inserted at these locations to accommodate this movement.

Patchwork Cracks
The formation of cracks in both bed and perp joints visible in localised patches can be a sign of brick tie failure in cavity wall construction.  In less severe cases prior to the formation of cracks an increase in porosity of the joints resulting in a wetter darker look may be visible.  Examination of the surface of the wall will reveal undulation in the surface corresponding to the crack locations.

Some types of cracking are visible only on the inside of a building.  This is particularly the case a problem prevalent in buildings constructed before circa 1960 in which outward movement of the gable wall results in a bulge at the mid-height.  Cracks occur at the junctions with ceilings.  This is remedied relatively easily by providing straps that tie the wall to a strong part of the building.

Face Spalling
In older buildings the face of bricks or stonework can often be seen to have spalled off.  This is the result of alternate exposure to frost and sun.  Water droplets trapped in the surface freeze and expand thus forming tiny stress failures in the surface material.  Exposure to the sun during summer month will form expansion of the now loosened material which may now fall away from the face.  Repeated cycles of this for many years results in increasing areas of wall affected by the problem.  In creased porosity of the surface further accelerates the problem.  Care is required in repairing this defect as replacement of the worse affected units while leaving less severe cases can in fact accelerate the deterioration of those that have been left.
 
 
Brick Arch Lintels

Brick arch lintels are popular in older properties constructed in solid masonry.   Wall thickness will vary according to the number of storeys constructed above the one of interest.  This will usually be nine inch or thirteen inch construction.  The outer face of the wall is carried by a brick arch which can be flat or semi-circular.  The remaining thickness of wall is carried on a timber lintel.  Deterioration of the lintel will place increased load on the arch which will in turn begin to fail.  A common remedy for this has been to insert a steel (or cast iron) bar below the arch.  Eventually the bar corrodes giving rise to horizontal cracks at the supports.  This can give the appearance that the pier between the windows has failed but this may not be the case. 

The remedy for brick arch failure is to remove the timber lintel a replace with a new timber or precast concrete lintel.  The outer arch can be repaired insitu by drilling vertically to insert stainless steel pins fixed with resin injected into the hole.

 
 
Brick Rot

Bricks (other than engineering bricks) will absorb moisture from the ground or continual condensation such that over decades the bricks will soften and loose strength.  The bricks could be replaced by more durable bricks with similar properties to those being removed or they can be repaired insitu by injecting resin into the brickwork.  This will bind together the brickwork and protect it from further softening while at the same time increasing the compressive strength of the bricks.