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The twelve categories

The order of precedence

Compiled by the Sitonce editorial team from the PSI Candidate Information Bulletin, NASCLA's own published material and the federal standards named belowUpdated 2 min readFacts verified 4 September 2026
The short answer

The contract states its own order of precedence. Typically the agreement prevails over the general conditions, which prevail over the specifications, which prevail over the drawings. Where the contract is silent, general principles apply.

Construction documents contradict each other constantly. The order of precedence is how that gets resolved without an argument.

The usual hierarchy

RankDocument
1The agreement itself
2Addenda, later ones over earlier
3The general and supplementary conditions
4The specifications
5The drawings

That is typical rather than universal. The contract states its own order and the contract governs.

Why specifications usually beat drawings

Because they are written in words and words are more precise about quality than a line on a drawing is.

The drawings tell you where and how much. The specifications tell you what and how good. Where they disagree about a material, the words normally win.

Later addenda beat earlier documents

An addendum issued during bidding modifies what came before it, and a later addendum modifies an earlier one. Questions describe a conflict between a drawing and an addendum, and the addendum governs because it came later.

Scale against dimension

A written dimension governs over a scaled measurement. Drawings distort in reproduction and scaling is unreliable.

This appears as a question in its own right, and the answer is always the written dimension.

What to do when you find a conflict

Ask, in writing, before proceeding. Building to your own interpretation of a conflict makes the outcome your risk.

A request for information is cheap. Rebuilding a wall is not.

Common questions

What is the order of precedence?

The hierarchy deciding which contract document governs when they conflict. Typically the agreement, then addenda, then the conditions, specifications and drawings.

Do specifications beat drawings?

Usually. The specifications describe quality in words, which is more precise than a line on a drawing.

What about a written dimension against a scaled one?

The written dimension governs. Scaling is unreliable because drawings distort in reproduction.

Where does an addendum sit?

Above the documents it modifies, with later addenda over earlier ones.

What should I do when documents conflict?

Ask in writing before proceeding. Building to your own interpretation makes the outcome your risk.