Common Defects in Brick Masonry Works
Masonry has a very long tradition of being built by craftsmen, without engineering supervision applied to reinforced concrete construction. Nonetheless, errors do occur and defects show up when proper operating procedures aren’t followed. Below are some common defects in brick masonry as a result of workmanship errors:
1. Improperly Mixed Mortar
Mortar strength and the strength of the bricks are directly related to one another. Mixing mortar requires very specific mixing ratios of cement to water be adhered to otherwise, the sturdiness of the brickwork will be compromised, and it can become porous and vulnerable to water damage.
2. Bed Joints That Are Too Thick
A bed joint is a horizontal layer of mortar upon which brick is laid. If they’re too thick, the result will be reduced masonry strength because the extra thickness will generate higher lateral tensile stresses. For example, a bed joint that is 16-19 mm thick will have 30% less compressive strength than one that is only 10 mm. A joint that is too thick even has the potential to collapse during the working process.
3. Bed Joints That Are Filled Improperly
Making sure that the bed joints are completely filled is vital for brickwork. Incompletely filled joints can reduce the strength of the brickwork by as much as 33% according to test results.
4. Exposing Freshly Laid Bricks to Bad Weather
When brickwork has been freshly laid it should be protected from exposure to either extreme heat or old until the mortar has completely cured. When new brickwork is exposed to exceptionally hot weather the resulting loss of moisture due to evaporation may prevent complete hydration of the cement and as a result, the mortar will not be full strength. In the case of cold weather, it can cause a displacement of the wall from the vertical, which will also mean a loss of strength. Proper curing of mortar can be carried out by covering everything with polythene sheets. In cold weather, it may also be necessary to heat the materials if bricklaying has to be carried out in freezing conditions.
5. Not Adjusting the Suction of the Bricks
If water has been removed from the mortar by the suction of the bricks, it may have become too dry for it to recover its originally flat shape. If dry bricks are used then it will absorb water from mortar and mortar will become dry and cannot attain any strength. The resulting wall will be both weaker and less stable than it should be.
Bricks should be soaked in water long enough to allow for the water to penetrate the whole depth of the brick. However, you need to make sure that they are not soaked excessively otherwise the brick will not attach to the mortar properly. Bricks should be soaked for 8-12 hours and removed from the water 1 hour prior to being laid.
Other types of brickwork defects include:
- Efflorescence
Efflorescence is the term used to describe a common defect that results from the crystallization of excessive salts from the brick. When there are too many soluble salts present in brick and it comes into contact with water, those salts dissolve and appear on the brick’s surface in the form of a whitish powder, leaving a dullish look that can only be remedied by repeatedly brushing and washing the wall surface. First scrub off the white powder with a stiff scrub brush and water, then clean the brick surface with a biodegradable detergent.
- Shrinkage
Because brick is a porous material that absorbs water causing it to swell and then shrink when the water evaporates. This type of shrinkage then causes cracks in brick masonry joints. While this does not affect structural strength, it does compromise the overall look of the brick.
- Frost Damage
This is an issue most common with older brick or those that were under burnt during the firing process. When it comes to newer construction, frost damage tends to be confined to areas of severe exposure, or due to incorrectly specified brickwork frost resistance. It occurs through a combination of excessively wet brickwork and freezing temperatures.
- Bricks Containing Dirt, Dust, or Mold
Over time bricks will get dirty or have moss or mould growing on them. This is usually the result of exposure to pollution and other airborne particles that attach themselves to the bricks and mortar. This is not typically damaging to the bricks and can even be considered protective, but if you feel that the moss or mould or discoloration on your bricks is excessive or abnormal, then clean the surface as gently as possible.
The above list is by no means exhaustive. Defects in brick masonry are often the result of either less than exact workmanship, failure to follow specifications (or specifications that were incorrect in the first place) or use of inferior materials. However, age and prolonged exposure to the elements can and will do their work on even the most well-done masonry work.
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