Freeze the base condition first
Save the reviewed base estimate before calculating an alternate. Give the file a revision identity and record the drawings, specifications, addenda, and approved assumptions that define it. An alternate cannot be checked when its starting point changes during the comparison.
Later base corrections should be logged and deliberately carried into every affected option. Describe the base condition in plain scope language. Identify the assembly, material, system, location, performance requirement, and responsible trade already included.
Avoid labels such as standard option when the documents do not define what standard means. The description should let a reviewer locate the base quantities without relying on the estimator who built them. Map the base work to estimate lines before applying credits.
A deductive alternate is not simply a negative allowance. It removes defined labor, material, equipment, subcontract, and possibly indirect resources from identified lines. The map prevents the team from crediting a value that was never carried in the submitted base bid.
Keep unresolved base scope outside the alternate calculation until its treatment is clear. If the base contains an allowance, state whether the alternate replaces that allowance or changes only work around it. Otherwise the option may compare a defined alternate against an undefined starting value and imply more certainty than the documents support.
Translate each alternate into a scope change
Read the alternate description beside every referenced drawing, detail, schedule, and specification paragraph. Rewrite it as a list of physical changes. Separate items added, items deleted, items retained, and items modified.
This working list is more precise than copying the bid form label into a single estimate cell. Mark geographic limits. An alternate may apply to one floor, elevation, room type, phase, or equipment group rather than the whole project.
Tie each quantity to that limit and note any matching work outside it that remains in the base. Location control is especially important when repeated assemblies look similar on a summary sheet. Follow interfaces beyond the named product.
A finish substitution can change substrate preparation, trim, transitions, protection, or installation sequence. An equipment option can change supports, power, controls, piping, access, startup, and commissioning. Include an interface only when the documents or an approved decision assign it to the priced scope.
Record exclusions that remain unchanged. The alternate sheet should show what was considered and left outside the price, with a document basis where available. A narrow exclusion is easier to review than a broad statement that all unspecified work is excluded.
Measure the net quantity change
Build an alternate takeoff that shows the base quantity, alternate quantity, and net difference. Keep units visible. The three-column view catches errors that a stand-alone alternate quantity can conceal, such as measuring the new assembly without removing the original assembly from the same area.
Use the same measurement boundary for both conditions. If base roofing is measured on slope, do not compare it with an alternate measured in plan area. If the base wall includes openings, waste, and accessories, apply equivalent rules to the replacement unless the alternate documents establish a different requirement.
Separate zero-quantity changes from zero-cost changes. A material specification may change while area remains constant, producing a unit-cost difference. Conversely, a quantity may change while a quoted package remains firm.
Show the quantity logic and pricing logic independently so the reviewer can test each one. Retain takeoff references for both sides of the comparison.
Page labels, detail references, zones, and item marks should survive into the alternate record. When an addendum revises one portion, those references let the estimator reopen the affected population instead of repeating every option.
Price resource and execution effects
Extend the net quantities with project-approved labor and material inputs. Do not reuse a base unit cost blindly when the alternate changes crew composition, fastening, fabrication, handling, or testing. State the pricing source and effective scope so the difference can be updated without reconstructing the estimate logic.
Review equipment and access needs as a change from the base plan. A heavier component, different installation elevation, or revised sequence may affect lifts, cranes, scaffolds, temporary openings, or delivery planning. Carry only supported effects and identify the operational assumption behind each allowance or resource line.
Consider schedule effects without inventing a duration. Ask whether the option changes procurement steps, work sequence, inspections, temporary conditions, or return visits. When no approved schedule analysis exists, describe the exposure and keep the decision open rather than claiming a precise time consequence.
Check supervision, cleanup, protection, testing, closeout, and warranty deliverables. These items may not scale directly with measured quantity. The alternate record should state whether each remains unchanged, changes by a calculated amount, or requires a documented allowance pending further definition.
Document the pricing basis and uncertainty
Give every material alternate assumption a source, scope boundary, and reconciliation trigger. If design information is incomplete, say what the current price carries and what later document or decision will replace that basis. This is more useful than presenting a provisional number as a settled fact.
Use the project basis of estimate to keep general methods consistent, but keep option-specific decisions in the alternate register. The two records should agree on inclusions, exclusions, allowances, quote treatment, and governing document revision. The AACE International provides professional resources for cost engineering and estimate practice.
For alternate review, use that discipline to preserve evidence another estimator can follow through the comparison. General guidance does not support invented certainty, market forecasts, or blanket percentage adjustments. Review quote coverage separately for base and alternate work.
A supplier proposal may price a substitution but omit freight, accessories, field service, or removal of the base product. Normalize the quoted boundary before using its net value, and preserve the proposal date and stated validity without making claims beyond the document.
Reconcile the alternate for release
Map each option total to its bid form line and proposal description. Confirm whether the form requests an additive amount, deductive amount, total substituted price, or unit price. A correct estimate difference entered with the wrong convention produces an incorrect submission.
Recalculate extensions, signs, subtotals, and carried values from the frozen worksheet. Deductive amounts deserve special attention because negative values can be reversed twice between a worksheet and the form. Have the reviewer reproduce the submitted figure from the approved base and alternate summaries.
Compare proposal wording with the priced scope list. Every material qualification should match the estimate treatment, and the wording must fit the procurement rules. Do not rely on a clarification that the bid form prohibits or on a scope note stored only in an internal worksheet.
Freeze the reviewed alternate package with the base estimate, source register, takeoff comparisons, quotations, combination matrix, and approval record. A later addendum should create a traceable revision. It should not overwrite the evidence supporting the earlier price.
Run an option-focused peer review
Give the reviewer the unchanged base map and the complete alternate change list. Ask the reviewer to select quantities from both sides of the comparison, test interface assignments, and follow their extensions into the option total. Findings should name the source and estimate location rather than offering a general approval.
Test at least one valid combination and one prohibited or dependent combination. Confirm the treatment of shared costs, indirect changes, and repeated scope. This exercise often reveals a pricing rule that seemed clear while each alternate was viewed alone but fails when owner choices are considered together.
Close findings with corrected values or a documented reason for retaining the current treatment. Keep unresolved questions assigned to named roles and show the bid treatment allowed by the documents. A blank response is not evidence that an item has been considered.
Use a final trace test: choose any alternate amount and reproduce it from the frozen base condition, defined physical change, net quantity, resource pricing, shared-cost rule, and bid form mapping. If the trail requires memory or an unrecorded conversation, the alternate is not ready for release.
