DRAWING ADDENDA AND BID CONTROL
A revised total should
explain what changed.
Use a comparison by item and input revision to separate quantity change from specification, pricing and execution-basis changes.
A constructed comparison
This example uses a fictional line identifier and two invented drawing revisions to explain the method. It is not a client result or a claim about a completed project.
| Item | Revision A | Revision B | Change |
|---|---|---|---|
| Route length, line P-101 | 30 ft | 36 ft | +6 ft |
| Specified isolation valves | 2 EA | 3 EA | +1 EA |
| Defined support items | 4 EA | 5 EA | +1 EA |
| Removed branch component | 1 EA | 0 EA | −1 EA |
Do not net unlike items together
Six additional feet of route, a valve addition and a component deletion need separate estimate rows. Different materials, sizes or specifications should not disappear into one net quantity. Record each affected drawing and its revision so the comparison can be checked.
Freeze one pricing basis to inspect quantity change
If the purpose is to identify the effect of quantities, apply the same agreed pricing basis to both versions. A separate comparison can then show updated supplier quotes or rates. Otherwise the difference between totals mixes scope change with market-price change.
Separate execution-basis changes
A revision may affect more than permanent quantities. A different installation sequence, field closure or tie-in window can change labor assumptions or equipment duration. Identify the cost basis and reason rather than presenting the effect as extra pipe or an unexplained percentage.
Try the route revision formulas in Excel →
Keep a change register
- Document and revision identifiers
- Item description, system and measured unit
- Previous quantity, current quantity and delta
- Specification or package-boundary changes
- Pricing and execution-assumption changes
- Open questions and items awaiting information
A comparison supports bid review and change discussions; contract entitlement and approved change orders remain separate matters. State whether revision comparisons are included in the original estimating assignment or commissioned separately.