Contents:
Classification of construction defects
Construction defects can be classified using several criteria: where they occur, how they appear and what causes them.
Some defects seriously affect a building’s subsequent use: they may shorten the service life of certain floor structures, lead to failures or create situations that endanger people’s lives. Others are simply aesthetic defects, noticeable only by appearance, such as walls that have not been levelled properly.
By their effect on safety and use, defects include:
Critical defects are damage that may threaten safety or the continued use of a structure. For example, inadequate drainage can damage the foundation, but the degree of danger is determined from the structure’s actual condition.
Significant defects are damage that noticeably impairs performance and durability. Voids in concrete and exposed reinforcement require investigation: appearance alone cannot rule out a safety risk.
Causes of construction defects
Errors can occur at any stage: design, construction or use. Following the design and applicable technical requirements helps reduce risk, but does not remove the need to monitor structural condition.
1. Design errors
Design errors lead to many defects, which often become apparent during the building’s use:
Incorrect calculations
Errors in calculations of loads, material strength and other parameters can result in insufficient structural strength or additional work at later stages.
Failure to comply with standards
Designing without reference to building codes and standards can result in an architect or designer producing unsafe and inefficient structures.
Errors in design and survey work
Errors in design and survey work can lead to unsuitable structural solutions. Their consequences depend on the nature of the error and conditions at the site.
2. Errors during construction
Errors made during construction can significantly affect the quality of the finished building:
- failure to follow material-handling requirements, such as incorrect placement;
- use of poor-quality building materials;
- failure to follow construction methods.
3. Errors in use
Errors associated with a building’s use can also cause defects. These include improper use of rooms, for example changing their purpose without considering the design, which may overload structures.
A lack of regular maintenance increases the risk of damage accumulating. Timely inspections and repairs help detect and eliminate its causes.
Methods for detecting construction defects
Damage is identified through visual inspection, document review and structural investigation. A specialist selects the methods according to the material, the building’s condition and the purpose of the assessment:
- visual inspection;
- checking documents and comparing actual work with the plan;
- laboratory test data;
- instrument-based inspection;
- as-built documentation and the construction work log;
- measurements;
- verification tests;
Foundation defects
Foundation defects can have extremely serious consequences:
Corrosion of reinforcement in basement walls
Moisture, chlorides and concrete carbonation can contribute to reinforcement corrosion. Corrosion products expand and may cause cracks and spalling of the concrete cover.
Cracks
Cracks in foundations and walls may be associated with design errors, overload, uneven settlement and other causes. Danger cannot be determined from width or depth alone: location, progression, material and structural condition matter. New or growing cracks should be assessed with a specialist; where there are signs of danger, access to the hazardous area is restricted until an investigation.
Freezing
In cold climates, ground freezing and frost heave can affect foundations. Moisture-saturated concrete can also deteriorate during repeated freeze–thaw cycles. The cause is established with reference to the soil, drainage, material and design.
Ground settlement
When the ground subsides or sinkholes appear near a foundation, the cause is established and the condition of the foundation assessed first. Whether and how to strengthen it is decided from the investigation, rather than external signs alone.
Façade defects
A building’s façade is its ‘face’, and defects in this area can negatively affect both appearance and function.
Main façade defects:
Detachment of finishes
This may be caused by an unsuitable choice of materials or failure to follow finishing methods, such as using poor-quality adhesives or unsuitable drying conditions.
Cracks
Façade cracks may be associated with settlement, thermal movement or faults in the coating’s installation. Efflorescence, staining, peeling and blistering are separate signs of damage, rather than types of cracks; the cause of each must be established.
Mechanical damage
Mechanical damage includes chipped corners, gouges and grooves. Mould and other biological contamination are considered separately: they may indicate prolonged surface dampness.
Floor-structure defects
Floor structures carry loads and transfer them to supporting structures. Depending on the structural arrangement, they also contribute to the building’s overall spatial stiffness. Damage to them requires an assessment of load-bearing capacity:
Deflection and cracks
Deflection and cracks can occur because of overload, insufficient strength, calculation or installation errors, reinforcement corrosion and movement of supports. An investigation determines the causes and whether continued use is acceptable.
Rust and corrosion
In reinforced-concrete floor structures, prolonged dampness and a loss of concrete’s protective properties can contribute to reinforcement corrosion. Rust staining and damage to the concrete cover require investigation of the cause.
Concrete separation from reinforcement
Reinforcement corrosion can cause concrete delamination and spalling. Other causes of damage are also possible, including freezing of saturated concrete; the effect on strength is assessed from an investigation.
Roof and roof-covering defects
The roof and its covering protect the building from the weather, and defects can lead to serious problems:
Leaks
Incorrect placement of roofing materials can lead to leaks and damage inside the building. This can be caused by both design errors and poor-quality materials.
Ice formation
Inadequate ventilation and insulation can lead to ice forming on the roof.
Deformation
This can occur because of an unsuitable choice of materials or insufficient structural strength.
Photographic records of concealed work help preserve information about completed stages. In the 101 App, photo reports and attached files can be used to document work. These materials help reconstruct the sequence of events, but do not by themselves confirm the absence of defects or establish responsibility. The cause of damage and necessary measures are determined using documents, an investigation and other evidence.
Technical explanations of cracking, corrosion and investigation: National Park Service, Preservation of Historic Concrete (in English). These are general damage mechanisms, without transferring US legal requirements.
