Specifications gives the nature and class of work, quantity of materials and workmanship etc.) Drawings cannot give information about materials and quality, specification are useful during execution of work to control quality of constructions.
NECESSITY OF SPECIFICATIONS
1. To avoid misinterpretation of items of work by both the contractor and the employer
2. To check the quality of materials used and workmanship
3. To find the unit cost of each item.
4. To specify machinery used for different works.
The engineer is very careful in writing specification not to give any scope for the contractor to deviate (double meaning words usage should be avoided, and it leads to court of law in certain times).
TYPES OF SPECIFICATIONS
The specifications are divided into two groups namely,
1. General Specifications
2. Detailed Specifications
1. General Specifications: It gives the nature and types of materials used in different items of work. In general specifications brief description of different items, type of material, time frame for completion, type of contract. This gives the general idea of the work. Helpful for preparing of detailed estimate.
2. Detailed Specifications: This gives detailed description of different items accurately such as quality of materials, quantities of different materials, proportions of cement mortar and cement concrete, method of mixing concrete, source of different materials, type of conveyance from source to work site. method of measurement are available in detailed specifications to get the expected quality of work while execution.
GENERAL SPECIFICATIONS OF DIFFERENT ITEMS OF WORKS
Earth Work Excavation: For all engineering works foundation trenches are to be dug after marking the structure. Earth work calculation can be done by multiplying the length× breadth× depth of excavation.
•After foundation bed and masonry is laid filling of trenches are generally neglected or lesser rate is paid.
•Earth filling for trenches= Earth work excavation – (Bed concrete + Masonry)
• Earth work should not be taken up especially during rainy season otherwise seepage water bailing out is a problem.
•If the soil is loose it needs timbering for trenches.
• Earth work excavation and filling quantities are calculated separately because the pates are different.
•While digging trenches be careful about pipe lines, communication lines electric lines, drainage lines etc.,
Concrete in Foundation: Foundation concrete is generally allow thickness of 30 cm or 300 mm with proportion 1:4:8 (or) 1:5:10 and are measured in m³ (length× breadth× depth).
•In foundation concrete coarse aggregate size used are 40 mm
• Before laying the concrete bed level, sand filling, sinking must be done and checked properly./
Brick/Stone Masonry with Cement Motor:
The quantity of masonry can be calculated easily by multiplying the length x breadth x depth and the units are in m³. Generally brick masonry constructed with cement mortor proportion (1:6).
Damp Proof Course (D.P.C)
D.P.C. is provided over basement to arrest rising of moisture to super structure usually of 25 mm thick width C.C. (1: 1 1/2:3) by adding 1 kg of water proofing compound (acco proof/Impermo) for 1 bag of cement D.P.C. is measured in m² (length x breadth)
• Breadth taken should be basement width.
Reinforced Cement Concrete Works (R.C.C.)
The R.C.C. used for footings, columns, plinth beams, lintels cum sunshades, beams and slabs etc., quantity can be calculated by multiplying length× breadth× depth. and its units are in m³
•Before mixing the concrete the following items keep ready.
(1) Steel bars are free from corrosion, scales, oil, grease etc., and are placed in position as per drawings and together with 20 SWG steel wire at intersections
(ii) Cement mortor blocks of proportion 1: 2 of 25×25 mm placed to get sufficient cover.
(iii) Materials like coarse aggregate 20 to 6 mm, Fine aggregate, cement and water ready.
(iv) Transporting concrete equipment like lifts/Chutes/Takaras/men etc., should be ready
(v) Mixing equipment should be ready with sufficient oil.
(vi) Centering and shuttering work should be complete.
Roofing : For R.C.C. roof the thickness of slab varies from 100 to 150 mm with minimum grade of concrete is M20 and is measured in m³ (length x breadth x depth).
In case roof is laid with manglore tiles/country tiles/GI sheet/A.C. sheet measured in m² (length× breadth).
Floor Finishes with Tiles and Marbles :
Basement is filled with sand, watering, ramming is to be done properly before laying bed concrete. The quantity of flooring is calculated by multiplying length x breadth and its units are in m².
For laying ceramic tiles a layer of C.M. (1: 3) is to be laid first over which these tiles are fixed with proper slope to drain water while cleaning. Joints are properly packed with different pigments. For bath rooms rough tiles are to be used.
For laying marble stones a layer of C.M. (1: 3) is to be laid and properly set the marbles well in advance are to be placed and fixed with white cement properly. While laying border can also to be added to get pleasing appearance. After laying the marble proper grindings is to be done to get required smooth finish.
Plastering and Pointing : Plastering is done to protect the masonry and to get good appearance. For brick masonry plastering is of 12 mm thickness and for stone masonry is of 20 mm.
•For stone masonry outside pointing is done with C.M (1/3)
•Plastering is measured in m² (length ×breadth).
•Plastering inside with C.M. (1:6) and outside is of C.M. (1:4) is done.
•Plastering for ceiling plastering is of C.M. (1:3)
•Deductions for doors, windows, ventilators, openings done as per the guidelines given below:
(a) For small openings upto 0.5 m² no deduction is made and no additions are made for jambs, soffits, sills etc).
(b) For openings area more than 0.5 m² and less than 3 m ^ 2 deductions are madefor one side only, other face is allowed for jambs, soffits, sills etc., (not to take separately).
(c) For openings more than 3 m² deductions are done on both faces of openingsand add the jambs, soffits, sills etc.
White Washing/Colour Washing:The quantity of white washing or colour washing is same as plastering item. l.e., breadth x height and its units are measured in m ^ 2
Painting : Payments will be made by measuring the area in m ^ 2 (length x breadth). Areas taken for doors and windows for painting or varnishing is of outer dimensions only.
• In the specifications priming coat, number of coats required and quality of paint required should be clearly mentioned.
• For painting doors and windows appropriate painting coefficient is to be selected and multiplied with area.
