A structural defect in a building is an actual physical damage to the designated load-bearing elements of the building. Caused by their failure which affects their load bearing functions to the extent that the home becomes unsafe, unsanitary or otherwise unlivable. Causing damage to persons, property and usually resulting in financial harm.

Building elements are either structural or non structural.

Defects to the non structural aren't that life threatening but could lead to some level of discomfort and the include: defects in brickwork,
Dampness in building,
Defects in plaster and tilework, etc

On the other hand, structural defects include cracks in foundation,
Cracks in floors and slabs,
Cracks in walls.
These are all serious signs that load bearing elements of the building have failed and if not checked could lead to total or partial collapse

All efforts are essential to prevent structural failure

There are several causes of this failure and there is a requirement for a proper analysis of all these factors before construction

Reasons why structures fail

One reason: defective construction !!!
Factors that lead to defective construction:

1) Defective design:
Where proposed loads have not been properly calculated and thus ACTUAL loading conditions of the structural elements have not been determined

Proper geotechnical analyses not done to ascertain soil bearing capacity and appropriate foundation
2) inferior construction materials:
Because loads are calculated for materials of specific characteristics, even a properly designed structure may fail if the materials are unable to withstand the load.

3) poor workmanship:
Even with satisfactory design, quality materials; actions and inactions of the building team ( skilled and unskilled) can result in failure

We have seen that improper design, inferior materials and bad workmanship are the factors that lead to defective construction.

It is therefore key that owners, designers and builders be adequately knowledgeable about these factors and undertake all preventive measures to avert them.

And here is a way:
Design:
Correct structural design, even a mistake or error is not acceptable!
Structural engineers are therefore required to be exceptionally careful and methodical when calculating for loads in all load bearing members of the structure.
All failure modes need to be examined using modern software on the subject

Proper soil investigation must be carried out and a detailed report presented to be relied on in designing the type of foundation

Finally, since the designer cannot be wholly confident about the design, an appropriate factor of safety is incorporated into the design calculations.

Thankfully our engineers apart from being overly playful in such forum as ours, are pretty good with what they do and are doing greatly with designs of structure and usually, building collapses recorded in this country are rarely their fault.

Inferior materials:
Materials for structural elements in buildings include steel reinforcement bars, sand, cement chippings, and water.
They are rarely inferior

This pushes the blame for structural defects in building construction to poor workmanship!

Poor workmanship:
Workmanship here spans everybody that is a part of the building team. From the consultant structural engineer to the artisan and the site help

The engineer who interprets the drawings on the site must be adequately trained and upto date with realities on the site.

Steel reinforcement bars of appropriate sizes must be properly tied and placed to achieve the desired strength in concrete members (all lappings must be to specified lengths)

Concrete being the chief material for structural members must be properly batched (according to specified ratio),
Properly mixed wether manually or mechanically with mixers (it is advised to mix large amounts of concrete mechanically to achieve uniform mix) with adequate water for specified slump.

Concrete must be properly placed and vibrated wether manually or mechanically with poker vibrators to expel trapped air from the mix and avoid "honeycombs"

Shutters must be properly fabricated, positioned and braced to receive concrete

Adequate concrete cover must be given for the reinforcement bars to avoid exposure to air and consequent corrosion.

Proper time must be given for concrete to cure before shutters are removed.

Gravity will help keep your building stable if all its vertical members are "vertical" else same gravity will pull the same building down if vertical members are not truly vertical.
So walls and columns must be made 100%vertical using spirit levels. Same with horizontal members except where slopes are required like in bathroom floors.

All these and other activities in the building site are made possible by good workmanship.
Here in Nigeria a mason with 10-15yrs experience automatically qualifies as an engineer!
A helper who sees the difference in pay between himself and his master resumes tomorrow with tools and parades himself as a skilled personel

It is therefore advised that building construction activities be left for professionals

Hand over your building project to a professional, pay his fees and leave him/her in charge...
And we can have a society devoid of the hazards of structural defects in buildings.

A collapsed building is an avoidable disaster!

A good read