Definition
The base bid is the price a subcontractor quotes for the core, fully-defined scope of work in your package — the work the drawings and specifications describe without optional add-ons or contingencies. It is the number you compare against every other bidder, because it is supposed to cover the same defined SOW for each of them. What sits outside the base bid is priced and evaluated separately: alternates (optional scope you may or may not accept), allowances (placeholder dollars for items not yet fully designed), and unit-price adjustments (changes to estimated quantities settled later at agreed rates).
For a heavy-civil general contractor reviewing the 5 to 15 bids it receives on a package, the base bid is the apples-to-apples anchor. Mixing alternate pricing or allowance dollars into the comparison rewards whichever sub structured its proposal most favorably rather than whoever offered the best price for the defined work.
A worked example
You receive three bids on a drainage package. Sub A submits a base bid of $1,200,000. Sub B comes in at a base bid of $1,175,000, but its proposal folds in a $60,000 allowance for unsuitable-material disposal that Sub A carried separately. Sub C quotes a $1,210,000 base bid plus an $80,000 alternate for an upgraded outfall structure. To compare correctly, you isolate each base bid for the defined scope: $1,200,000, $1,115,000 once Sub B's allowance is pulled out, and $1,210,000. The alternates and allowances are then evaluated on their own merits — not blended into the base-bid ranking.
Why it matters when you evaluate sub bids
Award decisions stand or fall on a clean base-bid comparison. If one sub's cover-sheet total quietly includes an allowance and another's does not, the raw numbers measure different things and your ranking is wrong before scoring even starts. Pulling alternates and allowances out of the base bid is what lets you level the field, score price against a like-for-like figure, and defend the selection to an owner. It also keeps later money — accepted alternates, drawn-down allowances, quantity adjustments — on a separate ledger you can track instead of burying it inside one headline price.
How Bid Reasoner handles it
Bid Reasoner reads each bid PDF and separates the base bid for the defined scope from alternates, allowances, and unit-price lines, so the price dimension scores on a like-for-like figure across all six dimensions — price, scope, schedule, compliance, performance, and risk. Two-way scope-coverage gap analysis confirms each base bid actually covers your SOW and flags anything excluded, with page-cited evidence quotes. The four deterministic risk rules then run on the leveled field: unbalanced unit prices at or under $1.00, peer outliers above 2x or below 0.5x the peer median, total-bid outliers beyond 20%, and front-loaded mobilization over 10% of total. The result is a base-bid ranking you can rank, override on the record, and export into the generated award documents.