The good news is that, generally, concrete, stone, brick and masonry walls and concrete or screeded floors that have cracks less than 1 mm wide (the thickness of a credit card) are common and usually do not warrant any corrective action. Most of these small tight cracks are caused by normal shrinkage as the moisture in the walls and floors evaporates over time or settlement of the structure which usually occurs within the first few years after construction.
Be warned, however, that changes in condition around the structure may also cause settlement many years later! Examples are planting a new garden or tree or removing a garden or tree that is against or close to the house.
Moreover, if a horizontal, vertical, or diagonal masonry crack is filled with hard masonry patching compound, any substantial future movement is likely to show up as a new crack in the patched area or nearby. Therefore, always use a non-shrinking grout to prevent stressing yourself!
Cracks that continue to move are a reason for concern! Continued movement in cracks should be evaluated as there may be a need for corrective action. Therefore, if you notice a crack has re-cracked or the crack has opened or gotten larger it should be monitored! However, first, make sure there is no shrinkage of the filler product. All cracks that are 5 mm and greater should be carefully monitored to ensure there is no continued movement.
Moisture absorbed into brickwork and plasterwork causes them to expand slightly. When the brickwork and plasterwork dry they contract slightly. The water absorbed by the bricks and plasterwork usually causes a slight vertical crack at the edges of the internal window sills. The paint then starts to bubble along the vertical crack. This crack may continue around the length of the window sill before you notice it. What started out as a small vertical crack then becomes a horizontal crack along the bottom of the window sill on the interior face of the sill wall.
The cracks are usually not significant unless allowed to continue unabated.
Sometimes the moisture intrusion at sills are mistaken for rising damp! Water leaking in at the window sill may bypass the damp proof course (DPC) built in under the window sill as a water-resistant barrier. The moisture may then appear as bubbling paint or crazing cracking of plasterwork, or both, below the window, extending down to floor level.
On external face-brick walls, this may appear as efflorescence (a white powder).
Internally, this may appear as bubbling paint above the skirting or discolouration of the skirting itself.
How do you prevent the moisture intrusion into window sills?
Trees can cause major damage to your home, garden and boundary walls. This is especially true on the Witwatersrand where most areas and soils have some clay content. Without care and control, they may cost you a lot of money and no small amount of effort to fix.
Furthermore, shrubs should not be planted too close to the masonry walls either. The building regulations specify a minimum distance of 1,2 m for normal soils and 1,5 m if you have clayey soil.
Roots can also grow beneath your foundation and lift the house or they can leach water from the ground during dry spells and sink or settle the house unevenly.
They will cause the soil to dry out and, in the case of clay soils, to shrink.
Any subsequent watering or extended rain periods will cause the clay to swell. In this way, trees and large shrubs can cause movement on clay soils resulting in damage to your home and walls.
The amount of movement depends on the percentage of clay content, the depth and extent of the root system and the efficiency of the tree to extract moisture from the soil.
When underground sewer and water pipes develop small leaks, roots will quickly take advantage of those leaks. Before you realise it you have a blocked sewer line and pools of water and sewage in your yard.
What not to plant
All trees should be regarded as a potential source of damage. The following varieties are, however, particularly prone to causing damage:
Most homes develop cracks. Old and new homes can develop cracks as well depending on climatic and physical factors.
However, it is worth getting to the bottom of what is causing the cracking. A crack is actually the visible symptom of a possible problem and not the problem in itself.
What causes cracks?
In new homes, settlement may cause minor cracks. Normal foundation settlement occurs when the underlying soil compacts as a result of construction on previously undisturbed soil, changes in soil conditions and moisture. Typically small, hairline-sized cracking may be the result of a minor settlement, expansion and contraction, or changes in a season or cycle.
Usually, these defects, though often unsightly, are not structurally significant.
Thermal movements between different materials
Different materials such as timber, bricks, steel, concrete etc. have different coefficients of linear expansion. In other words, the differing materials contract and expand differently. This causes stresses in structures where they are combined and may cause cracks to form. The best way to combat these defects in plasterwork is to provide a joint between the different materials.
In older homes, changes in climatic conditions can affect the structure. Houses move with the climate. Heat and moisture will make them expand, and cold and dryness will make them contract slightly. This movement is normal and in most cases will not cause cracking. Unusually hot or cold spells can result in increased expansion or contraction of the structure which may cause cracks.
The rise or fall of the water table in very dry or very wet conditions can also affect the house’s foundations.