05 - Structural Conditions
Visible damage to the building exterior is sometimes a good indication of the quality of construction. Even when a building is designed according to the latest version of the design codes, it will not perform as prescribed in the code if it is not detailed and built to certain requirements. One of the easiest means of determining the quality of construction is a visual inspection of the structure to determine any evidence of cracking, discoloration or distress, eg. spalling.
Cracking in reinforced concrete structures is the most obvious indication of potential problems. The reasons for cracking can be grouped into different categories and are identifiable by the location and geometry (width, depth and shape) of the cracks.
Poor concrete mix design, eg. too high water/cement ratio, structural settlement, reinforcement corrosion, improper curing (hardening), inadequate or lack of joints (crack control, expansion, construction, etc.), insufficient or lack of shrinkage reinforcement are just some of the reasons for concrete cracking.
So-called “hairline cracks”, a network of long, small-width cracks are to be expected during concrete curing and are not harmful.
Large-diameter cracks are to be treated immediately and the cause of the cracking identified as early as possible. These are harmful to the integrity of the structural elements as cracking results in the penetration of water into the concrete resulting in reinforcement corrosion, which weakens the structure with time.
A maintenance program that includes identification and monitoring of cracks, identifying discolored surfaces on concrete and steel structures, etc. is an important early warning tool.
If large cracks are identified a structural engineer is to be consulted to determine the cause of the cracking and propose mitigation measures. As a general rule of thumb cracks larger than 1 mm width are of concern.