How do you prove a construction variation?

You prove a variation by showing four things with documents: the original scope, the change, who caused it, and what it cost. Records made at the time carry far more weight than notes written later.

The four proofs

Original scope: the contract, the drawings, the specification and the tender allowances.
The change: the new drawing, instruction, email or site meeting note.
The cause: the person or document that ordered it, with a date.
The cost: timesheets, plant logs, supplier invoices and subcontractor quotes.

Records that win disputes

Dated site diaries that name the work and the people.
Photos with time stamps.
Emails that confirm a verbal instruction the same day.
A change register that links each change to its cost.

Records that cause trouble

Notes written weeks later. Costs rounded without a source. Messages in private chats. Missing drawing revisions. A gap in the story gives the other side a reason to refuse.

Questions

What is the single best habit?

Write down each change on the day it happens, with the source and a first cost.

Do text messages count as evidence?

They can. Save them with the date and sender, and confirm key points by email.

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