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IMPORTANT FACTORS TO REMEMBER ABOUT ALUMINIUM & GLASS PRODUCTS.

[ 5 minute read…]

Cracking is an indication or symptom of an underlying problem within the structure or element. It is the bond separation of elements or building sections to the extent where continuity is broken. By observing and analysing cracks, one can get a very good idea of the cause and reasons thereof.

The subject of cracking is very broad, but the three major categories to consider are:

  • Is the crack is Active, or Inactive? Are the cracks changing in length or width over time?
  • And, what is the duration of the crack development?
  • What are the 5 common types of cracks and when do you need to call a structural engineer?

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The other factors to consider are;

 

What is the element in question composed of?

  • Brick – Bricks have a tendency to ‘grow ‘over a period of years, creating internal stresses which are relieved through cracking of the structures. This is often noted as vertical cracking at the corners of older brick structures.
  • Concrete – Concrete structures will generally be steel reinforced, and any cracking noted should be further investigated.
  • Combination of Materials – As different materials have different rates of expansion, cracking is often evident along the interfaces between the two materials.

Where are the cracks located?

  • At openings – Stresses within structures concentrate around edges and corners of openings in buildings. Hence one will often see cracks emanating from the corners of windows and doors.
  • Beams, Columns & Slabs – Are the cracks located towards the ends or edges; or are they centrally located? The location of the crack assists in identifying the cause and source of the problem.
  • Position on Structure – Whether a crack emanates from the top or the bottom will generally signify the type of movement being experienced by the structure i.e., an upward or downwards movement.

Shape, Length & Width

Cracks are categorised in terms of severity. This categorisation is based on shape, length, and width. In an active crack, the categorisation will change over time. This change can be either increasing or decreasing, dependant on the cause of movement.

Crack Pattern

  • Regular Horizontal & Vertical – Regular crack patterns usually coincide with underlying separation or weak points, such as construction or expansion joints.
  • Diagonal, tapered, and parallel – These cracks are a good indication of structural movement within a building or element. These cracks will generally extend through the building or element. In brickwork, these cracks generally follow the mortar joint-lines in a stepped pattern – but sometimes do run through brick units.
  • Crazed cracking – These cracks are often noted in plaster work and new concrete, and are usually a result of shrinkage cracking. The cracks follow no particular pattern and are haphazard in appearance. [ click here to download our 5 common types of crack patterns and what to do about them ]

Discolouration and Salty deposits

  • Discolouration – A reddish brown discharge from cracks within concrete is a good indication of underlying spalling within concrete under moist conditions. Not all spalling however will exhibit this staining.
  • Stalactites – White crystallization and the forming of stalactites under slabs and beams are as a result of dissolved salts within the egressing water, through small cracks in the concrete element.

Mechanical Damage

Physical / mechanical damage to buildings and structures is attributed to accidental over-loading or impact. Cracking of the structures or elements can be caused by impact loading of vehicles, or dropping of heavy loads, which exceeds the original design capacity of the element.

 

Further Notes

The above is not an exhaustive list of crack types, and causes, but serves an as indication of what can typically be expected. In most instances, common sense and logic should prevail in making the decision as to whether an engineer should be called upon for assistance, with remedials and specifications. A qualified person should usually be able to advise – from a visual inspection – the nature and cause of the cracking encountered.

This guideline was written by Hiscutt & Dray Consulting.

For more information please contact them on (+27) 31 701 8406 or email them on admin@hiscuttdray.co.za

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