Specification [6 Hours]

12.1 Purpose of Specifications 20792072

Specification is the document where the level of intended quality is specified. They are clear concise descriptions of materials and workmanship including the methods of construction and precautions to be taken.

Purpose of Specification 2079 2072

• Helps avoid lengthy descriptions in bills of quantities and big captions on drawings. It supplements the information given in the drawings
• Serves the bidders to guide about the client's intended quality requirements and to arrive at a fair price for the work involved
• Part of contract documents between owner and contractor, limiting and describing their risks and responsibilities
• Serves as a guide for supervisors, engineers, and fabricators regarding methods of construction, fabrication, installation of equipment and materials

12.2 Types of Specifications 20782077207420712070

Depending on the purpose served, specifications can be grouped as follows:

a. Contract Specification 2078 2074

Contract specification is developed for a construction or project to accompany the work. Divided into two types:

i. General Specification

• Describes the nature of the proposed work, qualities of materials and workmanship in general
• Gives the general description of equipment

ii. Particular/Detailed Specification

• Detailed written descriptions with schedule of quantities, specifying material to be used, its quality, workmanship, and the method of execution
• Usually written in the same sequence as items in the BOQ
• Part of contract document regarding materials, workmanship, and equipment

b. Standard Specification

Generally prepared and published by organizations which cover specific materials used by a specific trade or segment of the construction industry. Examples: Indian Standard (IS), Nepal Standard (NS).

c. Overall Performance Specification

Details in comprehensive but general terms what the client is looking for.

d. Manufacturer's Specification

Specification prepared by manufacturers for their products.

12.3 Importance of Specifications 20792078207520742073207120702069

Specification is an important document in contract management. Without specification, the tender/contract document is incomplete, baseless, and invalid.

• The cost of a unit quality of work is governed by specification
• Helps to verify and check the strength of materials involved in a project
• Helps to specify the equipment, tools, and plants to be used — enables procurement or hire in advance
• Helps to procure the materials required for a project — controls the quality of materials
• Serves as a guide for the site engineer
• Serves as evidence in case of dispute
• Changes in specification change the contract cost

12.4 Specification Writing: Technique & Standards 207920782075207220702069

Principles/Techniques of Specification Writing 2079 2078 2075 2072 2070 2069

1. Specification language: Simple and clear. Same tense; use of a noun is preferable
2. Brief as possible: Standard articles specified by references and code numbers
3. Fairness: Fair to all parties. Proper sharing of risks
4. Express: Requirement of each and every item
5. Avoid repetition: Repetition of information is avoided to avoid the possibility of contradiction
6. Inclusion of proper paragraphs:
   • Specification of materials
   • Combinations of materials
   • Preliminary works prior to construction
   • Installation of materials
   • Test, if any
   • Clearing on completion
   • Mode of measurements
7. Standard size and patterns: Commercial sizes should be specified; unusual dimensions should be avoided
8. Cross-references: Should be minimum as possible
9. Quality: Quality of materials and workmanship should be specified
10. Nothing impossible: Nothing impossible to achieve or not intended to be enforced should be specified
11. Brand options: While specifying brand of materials, options and choices should be given

12.5 Typical Examples of Specifications 208120802079207720732072207120702069

A0) Specification for Earthwork in Excavation 2079

Scope

This specification covers all earthwork in excavation for isolated footings in sandy soil, including pit excavation, trimming, levelling, and disposal of excavated material as directed by the Engineer.

Site Preparation

• The area to be excavated shall be cleared of all vegetation, debris, rubble, and organic matter before commencing excavation.
• Centre lines and dimensions of the footing pits shall be marked using lime, pegs, and strings as per the approved drawings.

Excavation

• Excavation shall be carried out to the exact dimensions and depths shown in the drawings or as directed by the Engineer.
• In sandy soil, proper shoring and strutting shall be provided to prevent collapse of the sides of the excavation pit.
• The bottom of the excavation shall be levelled and compacted. Any loose or disturbed soil at the bottom shall be removed and replaced with approved material and compacted.
• No overbreaking shall be permitted. If any excavation is done beyond the required dimensions, it shall be refilled with lean concrete (1:4:8) at the contractor’s expense.
• Excavation shall not be carried out during heavy rainfall. Any water accumulated in pits shall be pumped out before proceeding with foundation work.

Dewatering

In sandy soil, groundwater is likely to seep into excavation pits. Adequate dewatering arrangements (sump pumping, well-point system) shall be made by the contractor at his own cost to keep the excavation dry during construction.

Disposal of Excavated Earth

• Suitable excavated material shall be stacked separately for backfilling.
• Unsuitable material (organic soil, soft clay) shall be disposed of to designated areas as directed by the Engineer.
• Excavated earth shall be deposited at least 1 meter away from the edge of the pit to avoid surcharge loading on the pit walls.

Backfilling

After completion of foundation work, the sides of the pit shall be backfilled with approved material in layers not exceeding 150 mm, each layer watered and compacted to achieve required density.

Measurement

Earthwork shall be measured in cubic meters based on the actual dimensions of the excavation as per drawings. No extra payment for shoring, dewatering, or removal of surplus earth unless specified in the BOQ.

A1) Specification for Cement Sand Mortar 2073

Materials

• Cement: Ordinary Portland Cement (OPC) of 43 grade or 53 grade conforming to IS 8112 or IS 12269 respectively, or NS 049-2041. Cement shall be fresh, free from lumps. Partially set cement shall be rejected.
• Sand: Clean, sharp, well-graded natural river sand or manufactured sand conforming to IS 383 or NS 051-2041. Sand shall be free from clay, silt, organic impurities, and salts. Silt content shall not exceed 8% by volume for natural sand. Sand shall pass through IS Sieve 4.75 mm.
• Water: Clean, potable water free from oils, acids, alkalis, organic matter, and other deleterious substances. pH between 6 and 8.

Proportioning

Cement and sand shall be proportioned by volume using proper gauge boxes. For 1:6 mortar, one part of cement to six parts of sand by volume. For 1:4 mortar, one part cement to four parts sand.

Mixing

• Sand and cement shall be mixed dry on a clean, hard, impervious platform until a uniform colour is obtained.
• Water shall then be added gradually and the mixture turned over at least three times until a uniform, plastic, workable mortar of the required consistency is obtained.
• Only the quantity of mortar that can be used within 30 minutes of adding water shall be mixed at a time.
• Mortar that has begun to set shall not be remixed or reused — it shall be discarded.

Use

• 1:4 mortar — Used for brickwork, plastering of external walls, below DPC, waterproofing work, and structural elements.
• 1:6 mortar — Used for general brickwork above DPC, internal plastering, stone masonry, pointing work.

Measurement

Mortar is not measured separately; it is included in the measurement of the item for which it is used (brickwork, plastering, masonry, etc.).

A) Specification for Brick Work in Cement Mortar 2080 2079 2072 2071 2070 2069

Bricks

Shall be chimney burnt hand-cast bricks of first-class quality, approved by the Engineer, free from all impurities such as lime, iron, and other deleterious salts. These shall be well-burnt, sound, and shall give a ringing sound when struck with a mallet. The bricks shall conform to IS 3626 with IS 1077 or NS 01-2035.

Brick samples shall be randomly selected for testing — not less than 5 bricks per one thousand for each lot of construction work.

Cement Mortar

Cement mortar shall be mixed in the specified proportion. Portland Cement shall be used, conforming to IS 1958 or NS 049-2041.

Sand

Sand shall be natural river sand or pit sand conforming to IS 383-1952 or NS 051-2041. Sand shall be clear, sharp-grained, and free from organic matters. It shall be well washed if containing more than 5% clay, dust.

Water

Potable water shall be used for mixing mortar and curing.

Mixing

Cement and sand shall be mixed in the required proportion (e.g., 1 part cement : 4 parts sand) by weight. Mix in a clean, dry platform till bubbles cease to come up.

Laying

Bricks shall be laid in cement mortar with frog upward. Bricks shall be laid flush in cement mortar. The courses shall be truly horizontal. Joints shall be uniform in thickness. All joints shall be well filled with mortar.

Scaffolding

Scaffolding shall be sufficiently strong for all construction and must be approved by the engineer.

Curing

The brickwork shall be continuously kept well watered for at least 14 days after laying. At no time during the curing period shall the mortar be allowed to dry.

Measurements

The measurement shall be computed on the basis of length, height, and thickness. It is measured on the finished work. No deductions shall be made for openings of areas less than 0.1 sq.m and for bearings of lintels, beams, girders, and holdfast blocks.

B) Specification for RCC Works 2069

Materials

Materials shall be of the qualities specified and delivered to works at least 7 days before required for use. Water used in mixing shall be free from injurious acids, alkalis, organic material, or other deleterious substances — as clean as drinking water.

Cement

Portland cement complying with IS 1967. Delivered in packages with unbroken seal, marked with brand name and manufacturer. Stored in a dry place. Set cement removed immediately from work at contractor's expense. Tests shall be made as per IS specifications.

Aggregates (IS 383-1970)

General: Aggregates shall consist of naturally occurring sand and crushed stone. They shall be strong, dense, durable, clean, and free from veins. Flaky and elongated pieces should be avoided. Shall not contain harmful materials such as iron pyrites, coal, mica, shale, clay, alkali, glass fragments, seashells, or organic impurities.

Fine Aggregates: Natural sand or sand derived by crushing reliable gravel or stone, free from coagulated lumps. Shall contain no more than 3% silt on total weight by sedimentation test. Clay lumps, shale, soft fragments, and other deleterious substance not more than 5%.

Coarse Aggregates: Crushed stone, angular in shape. Friable, flaky, and laminate particles limited. 24-hour immersion weight gain not more than 10% for plain concrete. Los Angeles Rattler Test wear at 500 revolutions not more than 50%.

Measurement and Proportioning

Aggregate measured by weight or by volume (if approved) in a gauge box of correct and approved size. Cement measured by weight — one or more complete bags of 50 kg per batch. Normal proportions shall comply with specified quantities. Range: 1 part fine aggregate to 1.5 parts coarse aggregate up to 1 part fine to 2.5 parts coarse.

Reinforcement

TMT bars conforming to IS 1786-1966 or IS 1139-1966. MS bars conforming to IS 432-1966. Item includes supplying and fixing with 18 gauge MS binding wire. Reinforcement shall be free from pitting, loose rust, paint, oil, grease, or adhering concrete.

Mixing

Cement and aggregates thoroughly mixed together in proportions in a batch mixer. Mixed till uniform color. Mixing time inversely proportional to speed. Not remixed with addition of cement or water.

Cube Tests

During progress of work, 15 cm cubes made as per IS 1964 and tested per IS 516-1964.

Consistency/Workability

Determined by making trial mixes with dried aggregates. Workability checked at frequent intervals by slump test at commencement of each grade of concrete placing.

Formwork

Supply, erection, and removal of all types of formwork including props, struts, strutting, wedging, form oil, sealing. Measured in square meter.

Placing

Time between adding water and concrete placing operation shall not exceed 30 minutes. Concrete shall not be dropped from a height that may cause separation. Each layer compacted by ramming, tamping, or vibration to form dense surface free from honeycombing. Vibrators at about 450 mm centers.

Cover of Concrete

• Horizontal/vertical/inclined slabs: 15 mm or main bar diameter, whichever is greater
• Lintels: 20 mm or main bar size, whichever is greater
• Beams: 25 mm or main bar size, whichever is greater
• Columns: Main bars — 25 mm; bars exceeding 12 mm diameter — 40 mm
• Piles: 75 mm or main bar size
• Pile Caps: 50 mm or main bar size
• Raft/mat footing: 50 mm or main bar size
• General RCC footings: 50 mm or main bar size

Curing

Immediately after placing, concrete protected from loss of surface moisture for seven days minimum (Portland cement). Methods:

• Water covering
• Application of impervious paper/membrane
• Continuous spraying or water-saturated coverings (e.g., hessian cloth)

Measurement

Calculated weight in kg from sizes and lengths of bars. No allowance for cutting waste, rolling margin, or tolerances. No hooks required for ribbed steel.

C) Specification for Gabion Works

Gabions consist of steel wire mesh crates. Steel wire shall comply with IS: 280-1962. All wire galvanized with extra heavy coating by electrolytic process. Wire woven into hexagonal mesh with minimum 3 twists.

Assembly

Crates assembled by binding edges together using binding wire. Interval between laces approximately at regular spacing.

Filling

Crates placed in final position before filling. Vertical corners kept square by inserting 20 mm steel bar. Stones individually placed, bedded and bonded as in dry random rubble masonry. No stones tipped into crate. When filled, lids closed and bound with binding wire.

D) Specification for Stone Masonry Works 2073

Stone shall be clean, hard, unweathered. Length of any stone shall not exceed three times its breadth, and breadth shall not exceed 150 mm or 3/4th the wall thickness. Spalls not exceeding 2% of the wall surface area may be used for filling voids.

Bondstones: Minimum 10% by volume. Shall measure minimum 150×150 mm on exposed face and 450 mm into the wall. At least one bondstone in every 0.8 m².

Stones shall be hammer/chisel dressed. Natural bed shall be at right angles to the direction of load. Cement, sand, water as per brickwork requirements. No unbroken boulder used in masonry. Stone samples submitted to engineer for approval.

E) Specification for Plaster Work 2077

Materials

Cement and sand as specified. For example, cement mortar 1:4 (1 cement : 4 sand) or 1:3 by volume. Mixing in mechanical mixer unless hand mixing approved.

Workability

• Mortar: Specified consistency with only enough water to be readily workable and plastic for trowelling
• Grout: Pourable consistency with slump of 120 mm, tested per standard slump test

Mixing and Using Period

All mortar and grout shall be used within 2.5 hours of initial mixing. No mortar or grout used after it has begun to set. If mortar stiffens from evaporation, it may be re-tempered by adding water and remixing.

Plaster Work

• Surface to be plastered shall be brushed clean
• Mortar joints raked to 12 mm depth and scrubbed with stiff brush
• Surface thoroughly wetted, cleared of dust, loose materials, grease
• Contractor shall prepare a sample of at least 1 m² for approval before starting

Curing

By keeping plastered surface damp on all exposed faces. Curing starts during application and continues for not less than 7 days. In hot weather, all finished work shall be covered or wetted.

Measurement

Measured in square meter. No deductions made for openings up to 0.5 m².

F) Specification for Painting Work

Preparation

• All surfaces papered by sandpaper properly
• Cement plaster surface: Apply thick paste of primer and smooth after drying
• Timber with knots and nail holes: Apply stopping and knotting materials (pure shellac dissolved in methylated spirit)
• Metal surfaces: De-rust and properly clean after sandpapering

Application

After preparing the surface, priming coat shall be applied as per manufacturer's printed instructions.

Measurement

Measured in square meter (flat). Include for two or more coats inclusive of all labor and materials complete.

Important Things to Consider