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OPERATING MANUAL CONSTRUCTION ACTIVITY SARVA SHIKSHA ABHIYAN SCHOOL EDUCATION DEPARTMENT GOVERNMENT OF WEST BENGAL. SIMPLE GUIDELINE AND SUGGESTIONS FOR PEOPLE CONSTRUCTING SCHOOL BUILDINGS. Dr. B.B. Niyogi Chief Engineering Advisor School Education Department Government of West Bengal.
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OPERATING MANUAL CONSTRUCTION ACTIVITY SARVA SHIKSHA ABHIYANSCHOOL EDUCATION DEPARTMENTGOVERNMENT OF WEST BENGAL
SIMPLE GUIDELINE AND SUGGESTIONS FOR PEOPLE CONSTRUCTING SCHOOL BUILDINGS Dr. B.B. Niyogi Chief Engineering Advisor School Education Department Government of West Bengal
1. a. First Consideration Budget One should start construction with a budget for instance, you could a budget based on an area that you have available for construction say @ Rs. 500/- per sqft poor planning needs to major over run tropically to major expenses cost of land and cost of construction. Selection of a Plot The critical decision before starting construction is to decide the location and size of plot. Size of the Plot Size of the plot should be depending on size of the building and the length-breadth ration of the plot should not exceed 1:2.
Legal Aspect • Utmost care should be taken with respect to all transactions involving land. After having ascertaining the bonafides of the land, it would be advisable to appoint a good lawyer to ensure clear title of the land.
b. Assistance that to be taken A Check List • Check List 1. Architect/Engineer 2. Contractor 3. Painter 4. Electrician 5. Carpenter 6. Mason 7. Plumber 8. Supplier of Building Materials 9. Neighbours 10. Guardian and VEC Member
1. Architecture/Engineer: Please make sure that choose a reputed Architect/Engineer from near by area where school is being constructed 2. Contractor: The contractor is responsible for arranging and supervising the workmen for different activities of construction. Contractors are generally paid either on per square foot basis or in terms of labour employed. It goes without saying that the reliability of your contractor defines the quality and durability of the construction.
3. Carpenter: The carpenter handles any woodwork – the making of doors and windows, frames for grills and related fittings and furniture for the house. 4. Painter: After completing the construction process, the painter can correct any minor detects and paint the house to achieve the desired look. Information on painters is available at paint stores or you could get a recommendation from an acquaintance who has recently painted their building. 5. Electrician: All of the electrical layout and wiring is designed and completed by the electrician. Please ensure that only licensed electricians are employed for this activity. Electricians can normally be contacted at electrical equipment shops in the area.
6. Mason: Laying concrete and bricks, maintaining proper even levels and surface layouts – implementation issues like these are the responsibility of the mason. 7. Plumber: Water supply, sanitation and waste disposal are important elements for any house. The plumber will help you design the best location and layouts for these. He will also help you install sanitary ware and pipes. For references, ask at sanitary ware and hardware stores.
8. Building Material Suppliers: Purchasing all building materials from authorized dealers of reputed companies is one way of ensuring a durable, long-lasting home. It is advisable to check specifications prior to purchase. Looking for low-cost options may lead to substandard results in construction. 9. Neighbours: Some useful tips can be picked up from people who have recently completed constructing their own homes. These tips could help in avoiding pitfalls, and lead to major savings in time and cost.
There are two types of rate contracts for construction: • A turnkey rate contract, which includes cost of construction, labour and cost of building materials. • Labour contract rate, which excludes cost of materials. • In practice, people who are able to devote time to the construction process opt for option 2. If, however, option 1 is chosen, please ensure that both the quality and quantity of materials to be used is discussed beforehand.
Some Tips for saving Time and Money • Understand the present and future needs of your school. • Ensure that the construction plan, working drawing and the estimated costs are in place before starting construction. • Ensure maximum natural light in all the rooms by providing adequate number of windows and ventilators. • Avoid non-standard size doors and windows or eliminate them altogether, if not necessary. • Use materials available locally. Contd.
·Plan for regular supply of materials beforehand. This avoids delays in construction. · Maintain minimal stocks of construction materials at the site. ·Stock all the raw materials properly so that they are safe. · Fixtures and fittings should be chosen for durability rather than just appearance. ·Electrical points need to be minimized. · If air-conditioning is to be used, plan the location in advance.
Table showing Material required to Construct 1 cum of Concrete Work
Table showing Material required to Construct 1 cum of Brick Mortar
Table showing Material required to Construct 12 mm Plaster for 100 sqm
Sand Procedures for Identifying Good Quality Sand: • Good quality sand can be identified easily by taking a handful and closing your fist around it. Any form of contamination like mud will stick to your palm. The presence of clay, grit, pebbles or dirt could be harmful in construction. They need to be screened or sieved from the sand before use. • A slightly more scientific method could be to fill half a glass tumbler with sand, add water into the tumbler and stir. Any form of contamination could result in the water turning muddy. As a rule, if the content of mud or dust exceeds 4% of the total quantity of sand, the sand would be washed clean before use. In short, sand should not contain clay, dirt, mica or sea shells.
Wet Sand and Associated Problems Sand should not contain water. Generally, if the sand contains about 5% of water, then use 25% additional quantity of sand for construction. Sometimes construction labourers add too much water which is detrimental to durable construction.
Bricks and their Selection Bricks can be tested just by observation. Visually they should be in the correct shape with sharp corners. A uniform colour also ensures good quality. One test is to break a brick, it should not scatter into small pieces. Another process of testing is to strike two bricks against each other. Good quality bricks produce a ringing sound when struck with each other. Also, a good brick when dropped from a height of about a meter should not break. Another practical test is to soak a brick in water for about 24 hours. The weight of the brick before and after soaking should be checked. If the brick shows an additional weight of more than 15% after soaking, it should be rejected. For example, a dry brick weighing 2 kg should not weigh more than 2.3 kg after being soaked in water for 24 hours.
Steel Rods (Reinforcement Bars) Concrete has good compressive strength. However, it does not withstand tensile or bending stresses. To overcome this, reinforcement bars (steel rods) are placed inside the concrete to provide the necessary strength. Hence, the term Reinforced Concrete Cement. We suggest that only BIS certified steel bars should be used for RCC construction. It is essential to ensure when purchasing them that no rust is visible on the bars. The steel bars are normally fixed in pre-designed formats. So, be careful that all design requirements are strictly adhered to. • Cover Block Use of cover blocks are highly recommended to ensure that adequate concrete covers the steel bars. Cover blocks are normally made using mortar and should be of a thickness of 2 inch for footing, 1.5 inch for columns and ½ to ¾ inch for slab and beam structures.
Stone Gravel/Coarse Aggregates Coarse aggregates are normally small pieces of stone which give concrete its strength. The two most commonly used sizes are ¾ inch or 20 mm and ½ inch or 12 mm. At times both are used together in the ratio of 60:40 or even up to 70:30. While selecting the coarse aggregate, the following points should be kept in mind: • Coarse aggregate should be solid, in the shape of a cube and free from dirt. • Any form of contamination should be immediately removed. • The right proportion of large and small size pieces should be selected. This is to ensure that the space between the large stonechips is filled in by the smaller pieces.
Water Water should be free of all contamination when used in construction. Salty water or sea water should never be used for making RCC. It is advisable to use potable/drinkable water, as far as possible. Addition of excess water is detrimental to concrete. A low water to cement ratio makes the construction strong and durable. It is always useful to have containers of five or ten liters of water handy while carrying out construction. One bag of cement normally requires 25 liters of water.
Test of Quantity of Water As a general rule, after mixing the water with cement and other ingredients, a ball of concrete mix should be made. If this ball is thrown up in the air to a height of a meter, it should not break or crumble as this is an indication of excess water content. It would then be advisable to reduce water content in the mix immediately.
What to Look for when you buy Cement It is advisable to purchase only well known brands of cement from reliable sources. A few rupees extra is money well spent as an inferior quality cement could lead to significantly higher cost later. Remember that cement once used cannot be replaced or improved in the same way as you can do with tiles and other such work. Besides, the cost of cement is only a small percentage compared to the total cost of construction. As a rule, cement should constitute only 10%-14% of the total construction cost. For example, if the total expenditure is about Rs.5 lakh, the cost of cement is likely to be 10 to 14 percent, which is around 500 bags. At a premium of five rupees per bag for good quality cement, the cost of cement will increase by about Rs.2500/-, which is quite insignificant when compared to the total budget of Rs.5 lakh.
Proper usage of Cement • An optimum quantity of cement must be used for any construction. It is a myth that high grade cements can be used in lower quantities. If lower quantities of cements are used, then an additional quantity of water is required. This would mean a distorted water to cement ratio, and the result would reduce the strength and durability of the concrete. • A common misunderstanding is that high grade cements result in better results. The grade of cement only indicates its compressive strength after a period of 28 days. However, blended cement continues to increase in strength beyond that period. Therefore, with the long term objective of a lasting home, blended or composite cements are usually preferred. Yet another misconception is that quick seeking cement should be used. It is advisable to allow all concrete structures the requisite time for setting.
·Ask the mason or contractor to be patient if they complain about the time it takes to set. Slower setting cement does not necessarily mean that it will not provide long-term strength. ·Some people believe that the colour of cement determines its quality. This is totally untrue. The colour of the cement is determined by the quantity of the raw materials used in its manufacture.
Some Additional Tips • If you have doubts about the quality of cement, the first step would be to consult the manufacturer. However, this simple test will also suffice. Make a paste of a cement with one-fourth the quantity of water and make cubes or blocks of 50x50x20 mm size. Leave aside the cubes/blocks for a day. Test them to see how easily they break. If the cement is of good quality, the blocks will not crumble if you try to crush it with your fingers. • Cement is known to react with water and, therefore, protection from moisture is of paramount importance. It would be best to store the cement bags in an enclosed godown. Ideally, the bags should also be placed on a platform at least 6 inches above floor level, leaving a gap away from the walls. Normally, each stack should not have more than 15 bags. A ‘first in first out’ process should be followed. Cement should always be used within 2–3 months of its manufacture.
Formwork (Shuttering) This is the temporary formwork meant to support your construction while the concrete work is in progress. It comprises of wood props, plywood and steel plates. A good formwork should be strong, solid and without any gaps so that water leakage through through the joint or any gap is almost minimum. 24 gauge micron polythene sheet should be used to prevent any water leakage. Apply a layer of releasing agent (like diesel or grease mix) to the formwork where the concrete is to be poured. This enables it to be removed with ease and ensures a smooth finish.
Concrete Work For RCC work, the ingredients of concrete should be in the ratio of 1:1.5:3 (cement one part, sand 1.5 parts and coarse aggregates 3 parts). All of these items are measured by volume and are best measured using a container of wood or steel. Traditionally, the size of this container would be 350x250x400 mm, which holds 35 litres. While preparing the mixture, 25 litres of water must be added per bag of cement. If the mix is prepared in a machine, it should be mixed for at least 2 minutes so that the mixture blends well with the water. If you are mixing by hand, then it is advisable to prepare a dry mix of cement and sand in a tray. After blending, when the colour appears uniform, the coarse aggregate may be added and then finally add the water.
The concrete mix should be cast before it begins to set. Normally, concreting should be completed within 30 minutes to an hour. In case of any delay, do not add any more water just to improve its flowing consistency. The casting of concrete should be done continuously, i.e., layer over layer. The mixture should be poured from a maximum height of 1.5 metres. This avoids the ingredients separating. The mixture must then be properly compacted. It is best to complete this task with a needle vibrator. If this is unavailable, an iron rod could be substituted. This is done to ensure that there are no air bubbles in the concrete, as this would weaken it.
Brickwork • The following mortars are suggested: - for a 4 inch wall (divider walls in the middle of the house) cement:sand = 1:4 for a 9 inch wall (outer walls) cement:sand =1:6
Before beginning work, ensure that the bricks have been soaked in water for 8 hours. Do not use completely wet bricks as the cement mixture will not stick properly. • After joining the bricks, the correct cutting or raking of the mortar is essential. This helps the adhesion of the plaster. The thickness of the brick joints should not be more than 1 cm. The vertical joints should never be continuous. It is best not to lay bricks higher than 5 feet at a time, as the mortar should given adequate time to set. The task of joining should begin from 2 corners (3-4 layers). The parts in between should be filled within the leftover frames. The line level and plumb need to be continuously checked. Curing must be done for at least 10 days. In this context, please read the section on the quality of bricks carefully.
Plastering Plaster is the skin of your house. Just as our skin gives shape and texture to our body, and protects your house from damage caused by salts, acid and rain. It also makes your house look beautiful. Therefore, it is important to pay close attention to it. ·Ensure that the wall is slightly wet before starting the plastering. Dry walls adsorb water from the plaster and this will cause the plaster, in time, to fall off. ·Check that the mason has not prepared the mix for the whole day. The mix must be prepared only in small quantities; as much as will be used in an hour. Your mason can, however, keep a large quantity of dry mix ready.
· The usual mix proportion is: 1:5 to 1:6 for internal plaster 1:4 to 1:5 for external plaster 1:3 to 1:4 for the ceiling However, if the sand particles are very fine, 1:4 ratio mix is suitable for all three areas. · Use wooden float for finishing as steel floats can sometimes cause small cracks. · Curing should be done for 10–14 days.
Curing The process of maintaining moisture in the concrete is called curing. Concrete begins to dry after casting. So, the parts exposed to the environment should be cured to ensure that the concrete surface is never dry. This needs to be done continuously, till the mandated period of curing. Usually, 10-14 days of curing is considered optimal. It is best to make small curing ponds or bunds on flat or horizontal surfaces. For vertical surfaces, you may wrap jute or hessian cloth on the surface and then pour water onto it. This helps keep the surface wet for longer periods.
Electrical Works Select electrical goods for your house carefully (these must be ISI marked). ·Make provisions for switch boards at the beginning of construction, or it will clash with the décor of your house later on. ·Make proper arrangements for earthing in your house and have it checked regularly. ·Do not make several temporary connections from one point.
Avoid using too many joints in the electrical wiring. Use good quality wires and insulation material. ·To protect your electric equipment, use a fuse on every power board. ·Do not use extension boards for permanent connections. ·Keep the power supply cord safe from water, heat and oil. ·Keep electrical materials away from children. Note: Use electricity with restraint. Have your connections, wiring etc. checked regularly. Get your electric work done only from a registered or license-holding electrical contractor.
Plumbing ·Use good quality ISI marked GI pipes and fittings for the water supply. ·PVC pipes for sewage discharge are both durable and convenient. The joints of pipes and fittings must be leak-proof. They should be double checked before laying the tiles.
Painting Painting provides protection to the walls of your house as well as so much more. It is said that the colours of your house reflect your personality. The painting work is broken up into three parts: 1.Pre-painting Work 2.Surface Preparation 3.Painting Painting your Interiors step by step: · Clean the surface thoroughly with sand-paper. · Then apply a coat of good quality primer. If required, apply a second coat. ·Once the primer has dried, apply one or two coats of acrylic-based putty. ·Apply a further coat, or two or three coats. Thinner should be used as per requirement.
Here are some Suggestions to make the Painting Work Easy: ·If there is any dampness or cracks or other damages on your walls, have these repaired first. ·Select in advance the shades and colour schemes you wish to have on your walls. You can get help choosing the colours from catalogues, displays and show-rooms of well-known companies. ·Find out the entire product range of the company so you can select the colour that suits your needs. ·Choose light colours for outer walls. This will keep interior temperatures low. ·Also use light colours on internal walls where a lot of natural light is reflected.
