Construction variations: what changed, by how much, and what remains undecided
Construction variations start with a practical question: what changed from the project baseline? A drawing may have changed, a quantity may have been remeasured, or the drawings, specification and bill of quantities may disagree. Before discussing a price, separate the physical change, the quantity calculation and the contractual decision. This guide explains how to assemble a record that can be checked, without treating every change as an automatic entitlement to extra payment.
Identify the difference before calling it a variation
A single commercial request may contain several issues. Keeping them separate helps the client, designer and contractor check each part against the relevant information.
| What was found | What to compare | What still needs a decision |
|---|---|---|
| A different quantity under the same item | The baseline and revised calculations using the same unit and measurement basis | Which measurement and payment mechanism applies under the appointment or contract |
| A change in material, detail or scope | The original drawings and specification against the revised versions | Who instructed the change and how its effects are reviewed under the contract |
| A conflict or omission in the documents | The BOQ item, drawing, specification and clarification request | The agreed basis for the next calculation or work stage |
The labels variation, addition and quantity adjustment do not replace a review of the project documents. For both lump-sum and remeasurement arrangements, check the defined scope, instructions, measurement basis and change procedure for that project.
Keep a baseline that another reviewer can trace
- Baseline drawing: sheet number, revision and date, alongside the drawing showing the change.
- BOQ item: item reference, description, unit and the quantity used as the comparison baseline.
- Specification and instruction: the relevant detail or specification clause and the instruction or clarification request.
- Calculation boundaries: level, area, element and work stage; state whether the quantity is designed or measured from completed work.
Retain the original version alongside the revision. Renaming a file is insufficient if the reviewed sheet and revision cannot be identified. See the quantity calculation workbook guide for a traceable calculation structure.
An example of a quantity difference, without deciding its price
Illustrative example only: the baseline drawing gives 120 square metres of partition and the revised drawing gives 150, using the same opening and deduction rules. The arithmetic difference is 30 square metres. Record both drawing revisions and the calculation, showing additions and omissions separately where the partition layout has changed.
The figure 30 does not, by itself, establish payment entitlement, a unit rate or a programme effect. A review may also need to address a different partition type, removal of completed work or an interface with services. Mark unquantified issues as open questions rather than absorbing them into the quantity without explanation.
What to record when reviewing construction variations
- A stable change reference, date and the person raising the request.
- A short description with references to the baseline and revised documents.
- Original and revised quantities, additions and omissions, with units and calculation workings.
- Assumptions, missing information and questions raised for clarification.
- The rate source and review status, where pricing forms part of the appointment.
- The reviewer and decision status: awaiting information, under review, accepted or rejected, with a dated supporting reference.
A useful distinction: a checked quantity, a proposed price and a recorded approval are different states. Track them separately so that a populated value is not mistaken for authority to proceed or pay.
Make the BOQ clear before work begins
Item descriptions, units, specification references and trade boundaries give a more focused basis for discussing differences. If a detail is missing, record a specific question instead of silently filling the gap with an assumption. See reading the technical specification and preparing a professional bill of quantities.
An early review cannot eliminate construction changes. It provides a documented baseline when the design or work changes. This page concerns identifying and quantifying the change; see submitting variations for organising the supporting document pack.
Preparing an enquiry for a quantity review
Yaakov Avital is a registered building technician and quantity surveyor. For a quantity takeoff enquiry about construction variations, provide the relevant revisions, BOQ and specification, and explain what needs comparing. Deliverables and scope are agreed in a written quotation. Variation pricing, account checking, change administration and other additional services are considered separately; a quantity calculation is not contractual approval of a change.
Frequently asked questions
Is every quantity difference a payable variation?
The figure alone does not decide that. First identify whether quantity, scope or the measurement basis changed, then review the applicable contractual procedure and recorded decisions.
What if work appears on a drawing but not in the BOQ?
Identify the drawing and the item or omission, then raise a clarification with the authorised project role. Do not assume document precedence or additional payment without reviewing the contract.
Does a quotation prove the quantity?
A quotation states a proposed price and scope. Checking the quantity also requires measurement workings and references to the drawing, detail or measured work supporting them.
What should I send first?
The question, baseline and revised drawings, BOQ and relevant specification. Identify missing documents explicitly so that the scope of the review is clear.
* Created with AI for marketing, for illustration only. Not reviewed by Yaakov Avital and not professional advice. Every project must be checked on its own by a professional quantity surveyor and an engineer.