A revised drawing can change a quantity, a specification or the contractor responsible for an item. Updating only the estimate total hides those differences. A useful takeoff revision records the old document basis, the new instruction and the measured change before the bid is reissued.
This is a pre-bid addendum workflow. Pricing a post-award change under a construction contract is a separate task; see the change order pricing guide for the cost-recording questions involved there.
1. Log what changed before replacing files
Retain the previous issue and list the new sheets, schedules, specifications and written instructions. Record which documents the current workbook used. Ask the project team to resolve conflicting issue information rather than treating the most recently downloaded file as automatically governing.
Your revision register can contain:
- Drawing or specification identifier and old/new issue references.
- The building, floor, system or package affected.
- The instruction being priced, with a source reference.
- Status: unchanged, removed, added, remeasured or awaiting clarification.
- The corresponding workbook line and person responsible for review.
Revision clouds can help find changes, but do not rely on them alone. Check schedules, legends, notes and specification changes that may affect repeated items throughout the project.
2. Separate quantity, product and scope changes
| Change type | Example | What the estimate should record |
|---|---|---|
| Quantity | A footing length increases. | Old quantity, new quantity, unit and measured delta. |
| Product or assembly | A finish code or wall assembly changes. | Removed and replacement descriptions, including affected layers or accessories. |
| Rate | A supplier quote changes while the measured work stays the same. | Rate source and date, with the quantity held separately. |
| Responsibility | Equipment power moves between trade packages. | One named package carrying the item and the corresponding scope adjustment. |
| Execution | The instructed work sequence changes. | Agreed installation assumptions and any separate labor or equipment effect. |
One addendum can contain several change types. A larger slab may change concrete volume without changing the specified mix; a new mix specification can change the rate while leaving the volume unchanged.
3. Show the quantity delta with its units
Consider a worked footing example: width 2 ft, depth 1 ft, and an original length of 192 ft. An assumed revision increases the length to 204 ft while keeping width and depth unchanged.
| Quantity | Calculation | Result |
|---|---|---|
| Original base volume | 2 × 1 × 192 ÷ 27 | 14.2222 CY |
| Revised base volume | 2 × 1 × 204 ÷ 27 | 15.1111 CY |
| Base change | 2 × 1 × (204 − 192) ÷ 27 | 0.8889 CY |
| Change with an assumed 10% allowance | (24 ÷ 27) × 1.10 | 0.9778 CY |
Values are rounded for display; calculate from the unrounded dimensions. The allowance is an example, not a recommended percentage for every pour. This is not an actual issued client revision.
The volume difference does not establish changes to rebar, excavation, formwork or placement cost. Check those items against their own details and units. See the concrete takeoff scope and the separate worked revision record for related checks.
4. Keep the quantity effect apart from the rate effect
For one unchanged item description, old cost is old quantity × old rate and new cost is new quantity × new rate. If both inputs change, record both instead of labeling the entire difference a quantity revision.
An exact reconciliation is:
Cost change = (new quantity − old quantity) × old rate + new quantity × (new rate − old rate).
For example, 100 units at an assumed $20 become 110 units at $22. The original amount is $2,000 and the revised amount is $2,420. The quantity effect at the old rate is $200; the rate effect on the new quantity is $220. Together they explain the $420 difference. These are arithmetic inputs, not current construction prices.
5. Review interfaces and remove superseded work
Compare affected architectural, structural and MEP sheets together where the change crosses trades. If a wall moves, the impacts may include board area, finishes, devices and piping routes. Measure only the supported changes and flag unresolved routing or design details for clarification.
Do not leave the original item in the base bid and add the replacement as a second full item. Keep a revision history, but make the current bid’s included scope unambiguous. Alternates and provisional allowances should remain identifiable rather than being silently added to the base total.
6. Reconcile and issue the revised package
Check that the previous total plus additions minus omissions, with separately explained rate or allowance changes, reconciles to the new total. Identify the document issue, pricing date and remaining exclusions on the revised summary. Confirm which workbook and drawing-markup files the contractor should use for the bid.
Request a revision scope before the deadline
Send F&K both document issues, the previous workbook if available, the addendum instructions, affected trades and bid deadline. State whether the original takeoff was prepared by F&K or another party. A separate review may be needed before another estimator’s workbook can be revised reliably.
The estimating fee guide explains that addenda are quoted separately unless included in the accepted proposal. Use the form on this page to request quantity takeoff support or a commercial estimating package, with the revision boundary and delivery date agreed before work starts.