Common Mistakes Observed During Construction of a Building

It has been observed that a lot of mistakes/errors are made during construction of any structure/building. Construction mistakes can be identified as errors or inadequacies that can damage the building partly or wholly in one form or the other. One of the main reason of mistakes during construction is appointment of non-technical / incompetent contractor having little or no technical knowledge. These contractors during construction instead of consulting engineers, consult masons or owner of the house in case of any problem. If owner of house is an engineer or a person having some technical knowledge, he can guide or make appropriate suggestions, while a mason may suggest a solution which gives him more profit. Some engineers also give solutions which increases cost, and which indirectly increase the fee of the consulting engineer.

Drawing of plan, section, elevation, schedule of openings, bar bending schedule, structural drawings, drawings of electrification, plumbing, coloring schemes, etc. are necessary for proper construction. However, a few of the above, like electrification and plumbing are rarely drawn. Working drawings are not drawn and specifications are not given in detail, and even if they are given, incompetent contractors do not understand them and construction is carried out as per the masons understanding of the drawings and assumed specifications. This creates confusion and the quality of construction suffers.

Common mistakes observed

Foundation: In case of low-rise structures having less load, it is not a big problem, but in case of multi-storey buildings or tall structures, it is essential to have sufficient knowledge of soil underneath the structure. Bearing capacity of soil, its nature etc. are essential properties of the soil, hence, soil exploration is required to be carried out, though it is mostly neglected. Engineers presume less bearing power of soil and design foundation with larger factor of safety. As no borehole data is available, insufficient foundation depth is made. In rural areas, it is a common mistake in load bearing structures to construct stone masonry foundation in mud mortar.

In case of under-reamed pile foundation, the bulbs are not properly checked for its diameter at reamed portion. During construction of plinth beam in such cases, no air gap is provided below plinth beam to accommodate soil swelling pressure due to swelling soils, particularly in rainy season.

Reinforced concrete construction: In case of reinforced concrete construction, many mistakes are made due to insufficient and improper cover to steel bars, absence of stirrups, plain bars provided without hooks, lack of development length, sinking of negative steel during concreting of slab, not using vibrator to compact concrete, etc. In case of heavily reinforced concrete structures, the space between steel bars is so less that concrete does not flow properly in the gaps, which makes compaction of concrete difficult (as shown in Figure 1 and Figure 2). It causes segregation and no bond develops, it causes cracks to develop, which may cause collapsing of the structure.

Instead of using appropriate size of aggregate, either oversized or uniform sized aggregate is used. In case of uniform size, to make concrete consistent, excess sand is mixed which makes concrete weak. Cold joints are provided, but further concrete is carried out after a long gap without taking proper precautions. Working drawings and structural details are not drawn, which creates confusion in the site engineers. Poor communication between site supervisor/engineer and design engineer creates confusion, as site supervisor/engineers take decision as per their understanding and makes mistakes. These decisions are sometimes wrong, and the concreting carried out can lead to poor construction. Reinforcement is not checked as per drawings and are presumed correctly placed. Aggregates are not stacked properly, particularly fine aggregate i.e. sand. Sand is never washed before concreting as sand contains more quantity of silt and dust, affecting the quality of concrete. Many a times, bulky sand is used, which decreases quantity of sand and increases quantity of water, making concrete weak.

Masonry Construction: Quality of bricks used in masonry construction is hardly given any consideration. Now-a-days, instead of bricks, concrete blocks are used. Before using concrete blocks, it is essential that these blocks be tested for their compressive strength and used only if found to be good. But this is rarely done. Use of stale cement mortar and excess water in mortar in case of masonry construction and plastering/rendering is another mistake. Mortar is prepared once or twice a day and used by adding water throughout the day to maintain mortar’s consistency. Cement loses its strength and makes masonry weak. Bricks are rarely immersed/soaked in water; only some water is sprinkled on them and assumed that they are wet and will not absorb any more moisture; however, they do absorb moisture from mortar and make the masonry weak.

Construction of framed structure over load bearing structures is a common mistake made by owner as well contractor. Ground and first floor are load bearing and concrete columns are constructed at the junction of the walls for higher floors to use increased FAR. Even engineers and architects sometimes make this mistake. Long walls are constructed without cross connections. Doors/Windows frames are supported by half brick thick walls. In case of framed structure, infilled masonry is not constructed properly; this causes separation of masonry from frame as shown in Figure 3 and gives an ugly appearance.


Plastering/Rendering: In case of plastering, its thickness is very important. Thicker the plaster, more are the chances of its falling. In this case also mortar is prepared once in the morning and then used throughout the day by adding water to maintain its consistency. The cement starts its setting and loses its strength, making plaster/rendering weak. In case of infilled masonry, there are methods to plaster particularly at the top of masonry i.e. at the joint between masonry and beam soffit; however, since it is hardly given attention, it causes separation of wall with beam, giving an ugly appearance. Later on, it becomes costly to repair it. Ceiling plastering is another part where mistakes are made. Due to faulty construction of RC slab, the thickness of ceiling plaster varies from one part to another; and can become very thick in a few parts. This thick plaster in due course of time starts spalling, giving an ugly appearance and difficult to repair.

Formwork: Poor or weak formwork sinks during construction. Each formwork/scaffold has its certain designed useful life. If not changed, it collapses and can cause causalities. Use of wooden planks for slab formwork is also very common; this gives poor finish at bottom and increases thickness of ceiling plaster, and it falls many a times due to its uneven and greater thickness. Thick plasters do not form a good bond with concrete surfaces. It has been observed that many a times that the wooden post below slab formwork sinks during concreting. It gives a bad appearance to the ceiling. Sometimes, the formwork is removed early, but this is a wrong practice. Contractors do it to use it at other sites.

Steel Structures: Industrial shed with columns hinged at both ends and absence of lateral bracings and purlins not resting on truss joints but elsewhere are common mistakes made in erection of steel structures. Welding of members is another mistake, if the members are not properly welded as per design or welding is badly or barely designed and as such the joints are weak.

Waterproofing at terrace: Porous lime Coba at roof terrace i.e. poor waterproofing treatment is a common mistake due to rapid completion of work. No slope at roof is maintained so the water accumulates, percolates and causes rusting of reinforcing bars. Many a times, the contractor forgets to provide drain water pipes, or provides less diameter, which causes accumulation of water on the terrace. Therefore, rainwater drainage and downpipes should be well designed, specified and be provided.

Reverse slope over sunshade is also very common. Storage of heavy water tanks are made at roof level and that too at the center of slab i.e. at mid span. Sometimes, even heavy electricity generators are installed at roof level which are not designed for them, and not above beam/column but at mid span of slab. These generators transmit vibrations to slab which is not desirable.

Ignoring safety measures: Accidents on a construction site have adverse effects on property and can affect workers and the public. Accidents are unpredictable but the better prepared contractor and trained crew members/workers are more likely to be able to avert tragedies caused by accidents during construction. Modern technologies have made it possible to ensure construction staff follows the necessary safety norms. Using construction wearables help monitor factors like heart rate and stress levels on a worker and assess whether workers are fit to be onsite at that particular moment. Construction always has risks but having suitable safety systems means that one can work safely.

Staircase: The planning and design of staircase is most important and at the same time very difficult. The design of staircase includes details of pitch, risers and treads of staircases, handrails, spacing and design of balustrading. The area available to plan and design staircase should be sufficient, else a faulty staircase is constructed, and this becomes a major cause of accidents. As a rule, winders should be avoided, but one can find it in majority of the houses; this is due to poor planning and not providing required area for the staircase. Rise of more than 160mm must be avoided but a rise of 200 mm, particularly in residential buildings, is very common.

Plinth protection: No plinth protection in the form flooring of stone slabs / tiles / blocks is provided surrounding the building to drain off water in rainy season. This causes accumulation of water near the building which percolates into the ground. It makes soil muddy and causes sinking of the foundation. Plantation of large foliage / trees near a building is also a common mistake. The tree roots exert pressure on the foundation and may lift the foundation. This has been observed in single-storey load bearing structures constructed on black cotton soils.

Air voids in soils: Many a times, buildings are constructed on filled up soils. These filled up soils have huge air voids and need sufficient time to get naturally compacted. However, when buildings are constructed on such soils without getting them compacted, in due course of time and mostly in rainy seasons and due to weight of structures, differential settlement occurs as these air voids get reduced differentially at different places and the structure sinks. Floor sinking in such cases is very common. Even in hilly regions, structures are constructed on sloping ground, not having sufficient bearing capacity of soil, or having loose soil, either behind the structure or beneath the structure. Such buildings also fail due to landslides in rainy seasons. As these buildings / structures are constructed by owners without due considerations, they can flow away during landslides.

Change in slab thickness: Due to abrupt changes in thickness of slab from one portion to another, though precautions in laying of reinforcement bars is essential, it is not given any consideration. Sometimes, even engineers have little knowledge of laying reinforcement in such cases.

Surrounding soil removal: Sometimes, the soil adjoining the building is removed without taking precautionary measures. Boundary edge foundation is excavated without taking into consideration of abutting building, its life, foundation details, and effect of removal of soil of abutting structure. And if the abutting structure is old, chances of accidents are more.

Vibrations: Buildings are constructed either near railway tracks transmitting vibrations due to running trains or near shades having big machineries transmitting vibrations to the surrounding ground. Such buildings are required to be designed for vibrations transmitted, but this is aspect is rarely given any consideration. Structures should be designed with sufficient strength and ductility to absorb the energy released. Ductility allows the structure to deform without catastrophic failure.

Shape and size of room: Rooms, theoretically, are designed as having all corners rectangular i.e. having a 90-degree angle and modular in size. But this is rarely seen. It affects the laying of flooring tiles as the tiles are assumed to be of a particular size like 600mm *600mm, 300 mm,*300mm and so on, but are never of such sizes. They are always slightly small. So, tiles have to be cut unnecessarily. Moreover, as room corners are not rectangular, the last row of tiles to be laid vary in size from one end corner of the room to another end corner of the same room as shown in Figure 4.

Effects of mistakes

When some mistakes/errors are made, they have a direct effect on construction and have the following common effects:

• They cause cracks in structures which may be structural or non-structural.
• They unnecessarily increase cost of finishing items as thereby the cost of construction.
• Ugly appearance of walls, ceiling, slabs etc.
• Make structures weak, particularly the structural system like beams and columns, and can even cause structures to collapse.
• Mistakes can cause accidents and injure old people and children in the case of improperly designed staircases.

Conclusion

If all precautionary measures are taken and if competent contractor with at least a technical degree / diploma in construction / civil engineering or its equivalent, and with some knowledge of construction, the possibilities of mistakes occurring can be avoided and the built structure can be constructed safely.