Art and science of writing specifications

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.