CONSTRUCTION

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Introduction : As the ultimate owner of the property that you are building, you have a great role to play in ensuring that you are getting value for your money. That means you are getting a building that is durable and long lasting. Durability means that the building lives the life for which it is designed, which is normally 100 years.
The house that is being constructed should have following characteristics.

  • It should be completed within a specified time within the budget.
  • It should be aesthetic and beautiful to look at
  • The interiors are comfortable to live in
  • It should be durable and lives the designed life (say, 100 years).

This site offers some tips to you in this regard. The purpose is not to make you an engineer or architect. It is only to make you aware of certain important aspects of building construction for ensuring the durability of the structure and to help you to communicate better with your engineer or contractor. You are advised to engage qualified and experienced professionals such as engineers, contractors and the field level technicians for executing your project.

The System in India : The system through which an individual build homes in our country needs some discussion. There are three systems largely followed.

Self Management : Procuring all the material by the owner and hiring out the technicians on a daily wages basis and completing construction by self supervision. Suitable for small homes and extension works.

Self Management with only Labour Contract : Procuring all the material by the owner and hiring out the technicians on a labour supply contract basis. This will relive the owner from scouting for construction labour and so many hassles.

Turnkey Contract : Engage a building contractor on a per Sq.foot rate and turnkey basis and leave the rest to him. For example, you may appoint a civil contractor for Rs 500 per Sq.foot after some negotiations. He may also charge some Lump sum amounts for compound wall, drainage etc. A time limit is also the part of the contract.
With turnkey contract system, the advantage is that it is easier for you to build your home at a reasonable cost and you can avoid the cumbersome procurement of material from multi sources, storing, engaging and supervising labour etc.

Problems with Turnkey Contract System ( Sq.Ft Rate) : The problems in this system arises due to the lack of minimum awareness of the owner regarding the basic aspects involved in construction and lack of specifications of material and methods while awarding the contract. Even assuming that the contractor is genuine, qualified and experienced, the flat per Sq.Ft rate system has some flaws, in the absence of clear specifications.
Once a flat rate is finalized, how can the owner ensure that the contractor use the best methods and material to construct the home? The problem is compounded by the fact the bulk of material used in the country for construction is not standardized, except for cement and Steel. There is normally no quality control specified for Aggregates(Stones) and Sand. One has to simply trust the contractor in the quality aspects. If the contractor is greedy, he may use sub standard material, poor workmanship and methods that may save cost but weaken the structure. He may try to save cost to increase his profits.
In western countries, the practice is to engage a consultant who will liaise with the contractor and ensure the quality aspects. He will specify the material, methods and the quality procedures. He will take field samples and test in independent laboratories and certify the works. He acts as a bridge between the owner and the contractor and ensure the professional construction. The system may be slightly costly, but ensures quality.

What is the Remedy? : Engaging an independent consultant is obviously the ideal system to ensure quality construction. He will guide through the initial planning, specifications, contracting and supervision. The role of such consultant is to protect the owners interests in obtaining the expected quality.
But due to additional costs involved, one may hesitate to engage a consultant. In that case, what best can be done?
Following are some of the tips.

  • Understand what affects the quality and durability of the construction. Discuss with qualified persons, engineers and your friends who have constructed earlier.
  • While awarding the contract, give a specification of materials to be used. Alternatively, ask the contractor to supply the specification including the brands / quality of material he is going to use and vet the same with an independent civil consultant.
  • To the extent possible, insist using only standardized material (say, BIS) and well known brands.
  • Consider using independent testing agencies to test important specimens ( like compressive strength of Concrete). Include this as part of contract.
  • Ask the contractor how he is going to ensure the quality. Ensure that he follows what he commits.
  • Ensure that the material used is as specified.
  • Ensure that the proportions of the materials used are as agreed mutually.
  • Be sure about what to expect at each stage of construction.
  • Keep a measuring tape handy when you visit the site, and keep your eyes open.
  • When the work is going on visit and walk through the site. Ensure that the supervision is done by the contractor as promised.
  • You should not hesitate to ask questions about the process or progress of your home. If you see something that looks wrong, or out of place - ask about it without accusing your builder of missing something - chances are they know about it and are in the process of correcting or completing it.

Go through the other chapters of this section and develop minimum awareness of construction and where you have to concentrate. Don’t simply award the contract on a sq.ft rate basis and take the other things for granted. After all, your dream home should not only be beautiful but also durable ! Good Luck

Concept of Durability : The durability of concrete structures can be defined as their ability to sustain the serviceability or the life for which they were designed. Basic to the concept of durability is a commitment to quality and its assurance.
With respect to concrete, quality assurance is a matter of testing and inspecting to ensure the proper selection, proportioning, mixing, handling, placing, and curing of the materials, as well as the appropriate design of the structure itself.
Concrete Structures may face problems during their service such as :

  • Structural Failures
    • Cracking
    • Rusting of Bars
    • Sulfate / Chloride Attack
  • Surface Cracks
  • Segregation
  • Undulations
  • Surface Problems- Lime Leaching
  • Surface Problems- Lime Leaching

These problems reduce the life of the structure. Unfortunately, these problems may not manifest in the initial years. They may manifest themselves at a later date and by the time and the effects may become visible. Then we can not do much, except doing some repairs which may not cure the underlying problems fully.
Thus for civil structures, Quality Assurance is important than the Quality Control. Quality Assurance is preventing the problems in the first place by carefully choosing the materials, men and methods and ensuring output quality. Quality Control, on the other hand, checks the output quality with respect to the planned one and decides if the construction is alright or not. Obviously, if we find that the quality control detects failures in a constructed building, we can not break the structure and build again. Probably we may repair, but the underlying problems may not be corrected fully. Hence, it is wise to focus on Quality Assurance rather than quality control. Following are some of the means of assuring quality and prevent problems:

  • Prepare the building design, plan and specifications through a qualified and experienced engineer.
  • Ensure that the design is done after the soil test at the site where you are going to build the house.
  • Before engaging the building contractor, check his credentials and past projects executed by him.
  • Award contract in writing clearly stating the rates and specifications and mutually agree on the quality control and inspection procedures.
  • Ensure even in contracting stage that the contractor agree to use standardized and high quality materials only in the construction. If you know the good brands, discuss with the contractor and mutually agree.
  • Buy materials only from reputed companies, preferably with ISO-9001 certification for their manufacturing facilities.
  • Consider using Blended Cement variety for the construction. Some contractors may try to persuade you using High Grade Cements for his own benefits such as faster form removal.
  • Consider using Ready Mix Concrete instead of the conventional site mix concrete wherever possible to ensure quality and right mix design.
  • Visit the site when the works are going on and ensure that the contractor provides good supervision.
  • Ensure that the contractor stores the material such as cement in good conditions.
  • Ensure that the Reinforcement Bars are not corroded before placing in the form work.
  • Ensure that the materials of specified brands are used in actual construction.
  • Ask for the test results of cube specimens and note for any significant variations.
  • You should not hesitate to ask questions about the process or progress of your home. If you see something that looks wrong, or out of place - ask about it without accusing your builder.

Four Legs Concept : Any construction activity can be compared to a Table. Just like a Table has four legs, a construction project has four important components. Even if one leg fails, the table becomes unstable, and probably becomes unusable.
So is the case with the construction. Even if one of these four critical components fails, the total construction will be affected, irrespective of the fact that others are perfectly alright. Following are these components of construction :

  • Structural Design
  • Mix Design
  • Materials
  • Workmanship

Structural Design : Right Structural Design means that the members of the structure such as concrete columns, slabs, foundation, walls etc are designed to with stand the forces that will come on them. It deals with the sizes of these members and their placing in relation to each other within the structure. The Structural engineer analyzes forces affecting structural members in trusses, frames, beams, and columns, and calculates the resulting stresses and designs their sizes accordingly. If the structural design itself is faulty, irrespective of what materials you use, the structure will fail.

Mix Design : Mix design refers to design of concrete mix that involves specification of the proportion of materials like Cement, Aggregates, Sand, water and Admixtures that will give a specific grade and workability.
If the proportions are not correct or not maintained during preparation of concrete, the concrete may not develop necessary strength or durability. In conventional site mix concrete, the mixing is done manually and on volumetric basis. There is no quality control while making the concrete and there is a probability of excess water in concrete. All these tend to weaken the concrete. Hence it is advisable to use Ready Mix Concrete which is made in a batching under controlled conditions and through tight quality control through modern equipment. Quality, Grade and workability is assured . Click here to know more on Ready Mix Concrete.

Materials : The materials used for construction forms the third leg of construction. It is obvious that when substandard material is used, the construction quality suffers. To the extent possible, we must use only standardized material ( Like materials having an ISI Code) and reputed brands. The type and the brand of the material to be used must be clearly spelt out in the contract document.

Cement :

  • Cement is the binder that holds concrete and mortars together. It is used to make concrete and mortar for brickwork, plastering, flooring and other such work. Click here to know more about cement, its type and applications.
  • For the construction purpose, Blended Cements are the best. They give not only the strength but also durability better than high grade OPC Cement. Click here to know more about the benefits of Blended Cements.
  • Color of the cement does not have any effect on the quality of cement. There is a wrong impression that darker color cement gives better strength. In fact, darker color cement only gives scope for adding more sand than allowed in cement-sand mortar for plastering, which will give problems
  • Good brands of cement may cost 2 to 5% more but offer quality, consistency and reliability as well as 10 to 20% greater strength characteristics. Cement accounts for a mere 12 to 18% of the total expenditure on your home. So, using cheaper cement gives you little overall savings but a great risk!
  • Cement must be added to the concrete and mortar in a precise, consistent manner. Improper Water-Cement Ratios cause lower strengths, shorter design life and lower durability.
  • Cement must be stored dry, say by covering with tarpaulin, until final mixing into a construction material.

Sand : Proper selection of sand is critical in the durability and performance of your concrete mixture. It should be:

  • It should be a River Sand.
  • Must be clear, angular and hard free from clay, mica and soft, flaky material graded, which means it should be a mix of fine, medium and coarse sand free from contaminants like sea salt.
  • Moisture (water) content must be Consistent iwhich should not exceed 7%. When mixing concrete the moisture content must be taken into consideration.

Aggregates ( Stone Chips) :

  • They are major ingredient of concrete, giving it strength and solidity. The quality of concrete depends very much on the characteristics of aggregates used.
  • Stone chips should be angular or round, not flat or flaky.
  • They should not contain marks or layers of any other colour.
  • They should be free from mud and other impurities, which are harmful for concreting. It is advisable to wash the stone chips before mixing to make it free from dust, dirt and mud.
  • They should be well-graded. Which means these should contain sizes from 5mm to 20mm in proper proportion, so that voids are minimal.

Reinforcing steel : Reinforcing steel contributes to the tensile strength of concrete. Concrete has low tensile, but high compressive strength. The tensile deficiency is compensated by reinforcing the concrete mass through insertion of plain or twisted mild steel bars. Both branded and unbranded bars are available. It is wise to buy good brands like SAIL , the names of which are marked on the steel.

  • During construction, ensure that size and the type of steel reinforcement is provided exactly as per the engineering design specifications.
  • Steel bars/rods should be reasonably clean and free of rust.
  • Bars that cannot be easily bent manually or mechanically should be rejected.
  • Optimum length bars must be chosen to reduce wastage in cutting.
  • To avoid laps, shorter bars must not be accepted.
  • Welded lengths of bars should not be accepted.

Water :

  • You must use only potable water in quality concrete production.
  • Brackish or salty water must never be used. Contaminated water will produce concrete and mortars with lower durability, erratic set characteristics and inconsistent colour.

Bricks :

  • They should be show uniform texture and colour.
  • When broken, they must not leave lumps and grit.
  • Ensure that bricks are not made from saline clay. Look for proper and uniform burning.

Workmanship : Workmanship is the fourth pillar of Construction. The field level technicians like mason. plumbers, bar benders etc are very important components of a good construction. Also, the supervision quality matters a lot in ensuring the best.
Unfortunately, there is no educational qualification specified for most of the construction workers. In an industry, a welder has to be a qualified welding certificate holder; electrician must be ITI certificate holder etc. But in construction industry, the technicians are in the field by virtue of their experience and not by a formal qualification.
There may be some technicians who, due to lack of formal education and qualification, may hold certain view contrary to the ideal specified by the engineering principles. They may still believe that what they do is best, though the truth is on contrary.
Either due to poor awareness / skills or due to poor attitudes, workmanship fails, resulting in poor structures. Some examples of poor workmanship are :

  • Not curing the concrete structures properly.
  • Inability to select good material.
  • Not caring for proper storage of materials.
  • Not properly vibrating the concrete.
  • Adding water and diluting the concrete mix after it it is taken out of Mixture.
  • Walking on the reinforcement bars / form work before placing the concrete.
  • Not soaking the brick in water properly before laying.

Many of the problems of poor workmanship can be cured if the contractor provides adequate supervision by the trained personnel. Insist on this at the contracting stage itself.

 

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