Specification

A specification is a written description of the quality of materials, standard of workmanship, method of construction and mode of measurement and payment for each item of work in a project. Together with drawings and the bill of quantities, it forms the contract document.

Purpose

1. To describe the quality and quantity of materials, such as grade of cement, size of aggregate, mix ratio.
2. To define the method and standard of workmanship for each work item.
3. To guide the contractor on how the work must be done, and the engineer on how to inspect it.
4. To serve as the basis of the rate analysis, estimate and tender.
5. To fix the method of measurement and payment.
6. To control quality by giving tests and tolerances.

Importance in construction contracts

• Basis of the contract: it makes clear what the contractor has to supply, so tenders are comparable and fair.
• Quality assurance: work and materials below the specification can be rejected.
• Avoids disputes: the written standard settles disagreements between owner, engineer and contractor.
• Cost estimating: the contractor can price the work correctly; the owner can check the estimate.
• Supervision tool: the engineer inspects and approves against the specification.
• Uniformity: the same standard is followed by different contractors and work items.
• Legal document: it is used in claims, variations and arbitration.
• Safety and durability: it ensures the structure performs as designed.
• Basis for measurement and payment, which prevents overpayment.

Specification

A specification is a document that states the quality, quantity, workmanship, methods, tests and measurement and payment of each item of construction work so that the contractor can price and execute it, and the engineer can check it.

Types

1. General (brief) specification: a short statement of the nature, class and quality of the work and materials in the form of a general outline for a project.
2. Detailed specification: a full description of each item of work: materials, proportions, workmanship, testing, curing, finishing, measurement and rates. It is used in the contract.
3. Standard specification: published by an authority (DUDBC, Department of Roads, IS, BS) and used by reference.
4. Special / particular specification: extra or modified conditions for a particular project.
5. Performance specification: fixes the performance result required (strength, flow) and leaves the method to the contractor.
6. Proprietary / brand specification: names a specific product or manufacturer.
7. Method (prescriptive) specification: gives the exact materials and methods to be used.

General vs detailed specification

Specifications should be written so that they are clear, complete and enforceable. The main techniques and points to consider are:

1. Know the project: study the drawings, BOQ, site conditions and the type of contract before writing.
2. Use standard references: refer to Nepal Standards, IS, BS and DUDBC specifications, instead of repeating long details.
3. Be clear, precise and concise: use simple words, short sentences; avoid ambiguous words like "good" or "best" (quote measurable limits).
4. Be complete: cover materials, workmanship, testing, tolerances, protection, cleaning, measurement and payment.
5. Use a standard sequence for every item: scope, materials, workmanship, tests, finishing, measurement, rate.
6. Use correct technical terms and units (SI), and give grades, sizes and proportions.
7. Avoid contradiction and duplication with drawings, BOQ and general conditions of contract; say which prevails.
8. Be realistic and practical: the specified quality should be achievable with local materials and skills and should be economical.
9. Describe what is required (performance or method), not how the contractor should manage his business.
10. Allow for testing and inspection: state sampling frequency, tests and acceptance criteria.
11. Provide for rejection or correction of faulty work.
12. Use the proper tense and command form: "The contractor shall..."
13. Arrange by trade or work section, easy to find; use headings and numbering.
14. Review and update: check by another person and revise for changes in codes.

Detailed specification: brick work in cement sand mortar 1:4

1. Scope: Providing and constructing brick masonry in superstructure/foundation in cement sand mortar 1:4 (1 part cement : 4 parts sand by volume), complete as per drawings and instructions of the engineer.

2. Materials

• Bricks: first-class, well burnt, uniform in colour, shape and size (typically 240 × 115 × 57 mm in Nepal), with sharp edges, producing a metallic ring on striking. Compressive strength not less than 3.5 N/mm² (as per Nepal standard); water absorption not more than 20% after 24 hours; free from cracks, lime lumps and salts. Bricks are soaked in clean water for at least 2 hours (until bubbles stop) before laying.
• Cement: OPC 43 grade or PPC conforming to NS/IS, fresh and free from lumps; stored in a dry store on a raised platform.
• Sand: clean, hard, coarse, river sand, free from clay, silt, mica, organic matter and salt; fineness modulus 1.5–2.5 (zone II/III); silt content < 4%.
• Water: clean, potable, free from oil, acid, alkali and organic matter.

3. Mortar: Cement and sand are measured in boxes by volume (1 : 4), dry-mixed to a uniform colour, then mixed with the minimum water to a workable consistency. Mixing is done on a clean watertight platform or by a mixer. Only the quantity that can be used within 30 minutes is mixed; mortar that has begun to set is not retempered or used.

4. Workmanship

• The foundation bed is cleaned, levelled and wetted.
• The work is laid in English bond (or the bond shown in the drawing), with full headers and stretchers, and the vertical joints of alternate courses in line to maintain plumb.
• Bricks are laid with frogs up, pressed into a full bed of mortar, and all joints are completely filled.
• Mortar joints are 10 mm thick (not more than 12 mm), the face joints are raked 12–15 mm deep while the mortar is green for plastering, or finished flush/struck if pointing is specified.
• The walls are raised uniformly; the maximum height in one day is limited to 1 m; the work is kept plumb and level by plumb bob, spirit level and line; the surface is checked with a straight-edge.
• Toothing is left for joining new work, not raking back.
• The openings, lintels, sill and bearing of beams are as per the drawing; holes for services are provided.

5. Curing and protection: The brickwork is kept wet for at least 7 days by sprinkling, and protected from sun, rain and damage.

6. Tolerance and testing: Deviation from plumb should not exceed 5 mm per 3 m height; the thickness of the wall up to ±5 mm. Samples of bricks (compressive strength, absorption) and the mortar cubes may be tested as the engineer instructs.

7. Measurement and payment: The work is measured in cubic metres of finished masonry, in the net dimensions as built, deducting openings and other voids larger than 0.1 m²; no separate payment for scaffolding, curing and cleaning. Payment is at the contract rate per m³, which includes all materials, labour, tools, scaffolding, curing and wastage.

Detailed specification: brick work in cement sand mortar 1:6

Scope: Providing and constructing brick masonry in cement sand mortar 1:6 (1 cement : 6 sand by volume) for walls above plinth, including scaffolding, curing and cleaning, as per drawings and the engineer's instructions.

Materials

• Bricks: first-class, well burnt, regular in shape (240 × 115 × 57 mm), uniform in colour, ringing sound when struck, compressive strength not less than 3.5 N/mm², water absorption not more than 20%, no cracks or lime. Soaked in water for at least 2 hours before laying.
• Cement: OPC 43 or PPC, fresh, free of lumps, kept in a dry store.
• Sand: clean, coarse, river or pit sand free from clay, silt (< 4%), organic and salt, FM 1.5–2.5.
• Water: clean and potable.

Mortar: cement and sand in 1:6 by volume (gauge boxes), dry-mixed till uniform in colour then mixed with just enough water. Mortar must be used within 30 minutes of mixing; it must not be re-tempered.

Workmanship

• Brickwork in the bond shown (English or Flemish); full bed of mortar, all joints filled.
• Joint thickness 10 mm (max. 12 mm); face joints raked 12–15 mm deep for plastering.
• Courses level and plumb, checked by line, plumb bob and spirit level; vertical joints staggered.
• Raising limited to 1 m per day; toothing left for the next work.
• Leave openings, put in lintels and sleeves as per drawing; bearing for slab/beam finished flat.

Curing: keep wet for at least 7 days; protect fresh work from rain and sun.

Tolerance: plumb within 5 mm per 3 m height.

Measurement and payment: measured in cubic metres of finished work; openings over 0.1 m² deducted. The rate includes all materials, labour, scaffolding, curing and wastage.

The principles to follow in writing specifications are:

1. Clarity: the language must be simple, direct and have only one meaning; avoid vague words such as "good quality", "as required", "etc."
2. Completeness: all matters about the quality of material, workmanship, tests, measurement and payment must be covered so no important point is left to guesswork.
3. Accuracy: correct technical data, grades, proportions, sizes and references to codes.
4. Brevity (conciseness): no unnecessary words or repetition; use references to standards for long details.
5. Consistency: no conflict with drawings, BOQ and conditions of contract, and the same terms and units throughout.
6. Practicality: the requirements should be achievable with the available materials, skills and equipment, and be cost-effective.
7. Use of standards: follow national and international standards (NS, IS, BS, ASTM) and the norms of DUDBC or the Department of Roads.
8. Enforceability: the specified quality should be testable, with defined tests and tolerances so that it can be checked and rejected.
9. Logical order: arrange by work section, with the same sequence for each item (scope, material, workmanship, tests, measurement).
10. Flexibility and fairness: do not name a brand without allowing "or equivalent"; give an equal chance to all bidders.
11. Command form: say what the contractor shall do ("The contractor shall...").
12. Keep updated: revise the specifications when standards and methods change.

Detailed specification: cement sand mortar 1:4

Scope: Preparation of cement sand mortar in the proportion of 1 part cement to 4 parts sand by volume, for use in brickwork, plastering and other work.

Materials

• Cement: OPC 43 grade/PPC conforming to the relevant Nepal Standard/IS; fresh, free from lumps, stored in a dry shed on a raised platform and used in order of delivery.
• Sand: clean, hard, well-graded river or pit sand, free from clay, silt (< 4%), mica, salts and organic matter; fineness modulus 1.5–2.5 (for plastering finer sand, FM about 1.0–1.5, passing a 2.36 mm sieve).
• Water: clean, potable, free from oil, acid, alkali and organic matter.

Proportion: 1 : 4 by volume. One bag of 50 kg cement is taken as 0.035 m³, and a gauge box is used for measuring sand; for about 1 m³ of mortar around 8–9 bags of cement and 1.15–1.2 m³ of sand are required (indicative).

Mixing

• By mixer: dry mix until uniform, then add water for the required consistency, and mix for at least 2 minutes.
• By hand: on a clean watertight platform; mix dry sand and cement until the colour is uniform, then add water gradually and turn over at least three times.
• Water is minimum necessary for a workable mix.

Use: Mortar must be used within 30 minutes of adding water; if it starts setting it must be discarded; no re-tempering.

Testing: Compressive strength of 70.6 mm cubes about 7–10 N/mm² at 28 days may be checked as per the engineer's instruction.

Measurement and payment: Measured by volume (m³) when paid separately, otherwise included in the rate of the item in which it is used.

Detailed specification: cement sand mortar 1:6

Scope: Preparation of cement sand mortar of 1 part cement to 6 parts sand by volume, for general brick masonry, stone masonry and similar work where moderate strength is needed.

Materials

• Cement: fresh OPC 43 grade/PPC conforming to the Nepal Standard/IS, free from lumps and moisture, stored on a raised platform in a dry shed.
• Sand: clean, hard, well-graded river sand, free from clay, silt (< 4%), mica, organic matter and salts; fineness modulus 1.5–2.5.
• Water: potable, free from oil, acid, alkali and organic matter.

Proportion: 1 : 6 by volume; cement measured as 0.035 m³ per 50 kg bag; sand in gauge boxes with allowance for bulking of damp sand. Approximate material for 1 m³ mortar: about 5.5–6 bags cement and 1.2 m³ sand (indicative).

Mixing

• Dry mixing of sand and cement until the colour is uniform, then add water slowly and mix to a workable, non-segregated paste, either in a mixer or on a watertight platform by hand (turned at least three times).
• The least water that gives workability should be used.

Use: Used within 30 minutes of mixing; stale mortar is rejected and re-tempering is not allowed.

Strength: 28-day compressive strength of standard mortar cubes about 3–5 N/mm², tested if asked by the engineer.

Measurement and payment: By volume (m³) when separate; otherwise included in the item rate.

Writing specifications is both an art (clear expression and judgement) and a science (technical accuracy based on standards, tests and experience).

(i) Necessity of specification

• Defines the quality of materials and workmanship expected by the owner.
• Basis for estimating, tendering and rate analysis, so bids are comparable.
• Guide for the contractor and for the engineer's inspection and testing.
• Forms part of the contract and settles disputes, claims and variations.
• Ensures uniform standard, safety and durability.
• Fixes the method of measurement and payment.

(ii) Procedure of drafting

1. Study the drawings, BOQ, site, local materials and the contract type.
2. List the items of work and group them by trade.
3. Collect the standards (NS, IS, DUDBC, NBC) and previous specifications.
4. Write each item in a set order: scope, materials, workmanship, tests, tolerance, measurement and payment.
5. Use clear command language and exact numbers (proportions, thickness, strength).
6. Check for conflicts with the drawings, BOQ and general conditions.
7. Review by another engineer; revise and finalise; keep a master copy for updating.

(iii) What to write and what to avoid

What to write: the quality and grade of materials, tests and sampling, method of work and sequence, tolerance, protection and curing, measurement and rate; references to codes; special conditions and what is included in the rate.

What to avoid:

• Vague words ("good", "approved", "suitable", "etc.") without a standard.
• Contradictions with drawings and conditions of contract.
• Repeating the content of other contract documents or the general conditions.
• Over-specifying beyond what is practical or economical.
• Brand names without "or equal".
• Items that cannot be tested or measured.
• Unneeded long sentences, jargon and duplication.

Specification is very important in a road project because the road is built from many materials and operations (earthwork, sub-base, base, bituminous or concrete surfacing, drainage and structures), and the quality of each controls the service life.

• Quality of materials: it fixes the grading, CBR, abrasion value, bitumen grade and cement for the sub-base, base and surfacing.
• Method and standard of work: compaction level, layer thickness, temperatures for laying asphalt, curing and tolerances for levels, camber and smoothness.
• Quality control: the test types and frequency (field density, Marshall test, cube tests) so the engineer can accept or reject the work.
• Basis for tender and payment: each pay item (m³ of earthwork, m² of surfacing) has a clear scope, measurement and rate, as in the Department of Roads (DoR) Standard Specifications.
• Uniform standard for different contractors and sections of the road.
• Dispute settlement and extension of time or variation claims.
• Durability and safety: reduces early failure, pothole and rutting, saving maintenance cost.

Detailed specification: RCC M20 concrete in columns

Scope: Providing and casting reinforced cement concrete of grade M20 (nominal mix 1 : 1.5 : 3, characteristic strength 20 N/mm² at 28 days) in columns, including formwork, reinforcement, curing and finishing, as per IS 456:2000 and the drawings.

Materials

• Cement: OPC 43 grade/PPC, fresh and in good condition; minimum cement content 300 kg/m³ (IS 456 Table 5).
• Fine aggregate: clean river sand, zone II, free of silt and organic matter.
• Coarse aggregate: crushed stone, hard and angular, graded 20 mm down; flaky particles within limits.
• Water: potable; water-cement ratio not more than 0.50 (max 0.55 for mild exposure).
• Steel: Fe 415/Fe 500 deformed bars as per drawing, free from rust and oil.

Formwork: rigid, tight, plumb steel or timber/plywood shuttering with proper bracing, oiled with release agent. Cleaned and checked before concreting.

Reinforcement: cut, bent and placed as per bar bending schedule, tied with binding wire; clear cover 40 mm for columns (IS 456 clause 26.4.2.1) using cover blocks; lap lengths and stirrup spacing as per drawing.

Concreting

• Batching by weight preferably, or by volume using gauge boxes in a mechanical mixer; mixing for at least 2 minutes.
• Slump 50–75 mm for columns.
• Concrete is placed within 30 minutes of mixing, in layers of 300–450 mm, from a height less than 1.5 m to avoid segregation, and compacted by a needle vibrator to remove air voids.
• Place columns in a continuous pour; the construction joint at 25–50 mm below the beam soffit when needed.

Stripping of forms: vertical column forms may be removed after 24–48 hours (IS 456 clause 11.3).

Curing: wet curing (gunny bags or ponding) for at least 7 days.

Testing: cube samples (150 mm) at least one set per 5 m³ per day, tested at 7 and 28 days; slump tests; average strength not less than 20 N/mm² and no individual result below 16 N/mm² per IS 456 acceptance criteria.

Tolerance: column plumb within 5 mm per 3 m; size ±5 mm.

Measurement and payment: concrete in m³ (net, no deduction for steel), reinforcement in kg (as per bar bending schedule), formwork in m². Rates include all materials, labour, vibration, curing and scaffolding.

Detailed specification: 12 mm cement plaster 1:4 on brick wall

Scope: Providing and applying cement sand plaster 1:4 (1 cement : 4 sand) of 12 mm average thickness on brick walls (internal/external), complete with curing, as per drawings.

Materials

• Cement: OPC 43 grade/PPC, fresh.
• Sand: clean river sand, free from silt, clay, organic matter and salts; passing 2.36 mm sieve, FM about 1.5–2.0.
• Water: clean, potable.

Mortar: 1 : 4 by volume, mixed to a uniform consistency and used within 30 minutes; no re-tempering.

Surface preparation

• Brick joints are raked to a depth of 12–15 mm and the surface cleaned of dust, efflorescence and loose mortar.
• The wall is wetted thoroughly (not saturated) for a few hours before plastering.
• Masonry should have settled; pipes and electrical conduits are fixed first.

Application

• Level guide strips (screeds) of mortar, 15 cm wide, are fixed at 2 m intervals, truly plumb and in the same plane.
• Mortar is thrown firmly and pressed into the joints, filled between the screeds, and levelled with a straightedge (a flat wooden rule).
• The surface is finished with a wooden float to a uniform, even surface; for a smooth finish a neeru (cement slurry) coat may be applied with a steel trowel.
• Plaster is applied from the top downward, and junctions are cut clean and straight at the end of the day. Edges and corners are finished plumb and square.
• External plaster in one panel is done without joints; in case of joints, they should be at a corner or a groove.

Curing: Kept moist for at least 7 days, protected from sun, wind and rain.

Tolerance: thickness not less than 10 mm at any point; the surface should not deviate more than 3 mm under a 2 m straightedge.

Measurement and payment: measured in square metres of finished surface; openings up to 0.5 m² not deducted, larger ones deducted at one face; the rate includes materials, scaffolding, curing and labour.

Detailed specification: stone masonry in cement sand mortar 1:6

Scope: Constructing random rubble/coursed rubble stone masonry in cement sand mortar 1:6 in foundations and walls as per drawings.

Materials

• Stone: hard, sound, durable, free from cracks, weathering, soft veins and dirt; locally available (e.g. granite, limestone, or river boulders), compressive strength not less than 5 N/mm² and water absorption below 5%; stone size generally not less than 150 mm in thickness, and of length not more than three times the height. Face stones dressed to the line; stones are cleaned and wetted before use.
• Mortar: cement sand 1:6 by volume, with clean coarse sand, fresh OPC/PPC and potable water, mixed uniformly and used within 30 minutes.

Workmanship

• Foundation bed cleaned and levelled; the first course laid with the largest stones.
• Stones are laid on their natural bed in a full bed of mortar; joints are fully filled, and spalls (chips) are used to fill the gaps without voids. The hearting is packed with smaller stones and mortar.
• The stones are laid with good bond; vertical joints are staggered; a bond (through) stone is provided at 1.5 m intervals horizontally, and at least one for each 0.5 m² of the wall face for walls over 600 mm thick; for thinner walls, through stones extend through the whole thickness.
• The thickness of joints is not more than 20 mm for rubble; the corners and jambs are of selected, dressed stones.
• The work is raised evenly to a maximum of 1 m per day, and levelled at about 600 mm height by a leveling course.
• The face is kept plumb, checked by plumb bob and line.
• The faces to be plastered or pointed are raked 15–20 mm in the green mortar.

Curing: Wet curing for at least 7 days; protection from rain and sun.

Measurement and payment: in cubic metres of finished masonry. No deduction for openings below 0.1 m². The rate includes materials, scaffolding, curing and all labour.

Detailed specification: earthwork in excavation in sandy soil for isolated footings

Scope: Excavation in sandy soil for isolated footings of a multi-storey building to the lines, levels, and dimensions shown in the drawing, including shoring, dewatering, disposal, backfilling and compaction.

1. Site preparation and setting out

• The site is cleared of vegetation, debris and obstructions. The centre lines and the excavation limits are set out with pillars/pegs and lines by a surveyor, and approved by the engineer before work begins.
• Excavation size = footing size + working space of 300 mm on each side (or as directed).

2. Excavation

• Excavation is done by hand or by a backhoe excavator, to the depth in the drawing (not less than the depth recommended in the soil report; sandy soil generally has a bearing capacity to be confirmed by tests).
• Since sandy soil is loose, side slopes should be kept stable (typically 1:1 or flatter; vertical sides are allowed only up to 1.5 m with shoring) and timbering/shoring provided for depths over 1.5 m or if there is a collapse risk; neighbouring structures are protected.
• Excavated soil is stacked at least 1.5 m from the edge, or removed from the site to the place directed, and not on the building area. Usable soil is stacked for backfilling.
• The bottom is levelled, trimmed and cleaned. It is not disturbed or over-excavated; any over-excavation is filled with lean concrete at the contractor's cost.
• Water is removed by pumping and the trench is kept dry; ground water is drained away from the foundation.
• The bottom is compacted (e.g. by rammer) before PCC; the soil is verified by the engineer as per the design bearing capacity.

3. Safety: barricades, warning lights, safe access (ladders), no workers under the unsupported sides, and a safe distance for vehicles.

4. Backfilling: after the footing and plinth work, selected, clean and moist sandy soil is placed in layers of 150–200 mm and compacted by rammer or plate compactor to at least 95% of the maximum dry density.

5. Tolerances: ±25 mm in level, ±50 mm in lateral dimensions.

6. Measurement and payment: the work is measured in cubic metres of the net volume to the specified lines (footing size plus the working space allowed), at the contract rate per m³. The rate includes excavation, shoring up to the specified level, dewatering, disposal within a lead of 50 m and a lift of 1.5 m, trimming and backfilling.