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Estimating & Bidding

Alternates

In Plain English

Optional scope changes priced separately so the owner can adjust the project after seeing all bids.

Definition

Alternates are separate bid items that modify the base bid scope, either adding to or deducting from the base contract price. Owners use alternates to test pricing for optional scope changes while keeping the base bid consistent across all bidders. Both additive and deductive alternates are common in public bidding.

Why It Matters in Bidding

Alternates give owners pricing flexibility to fit a project to budget after bids open, but they create real work for estimators who must price each optional scope as a clean add or deduct from the base bid. On public projects, the order in which alternates are accepted can change which bidder is lowest, so the award math depends on alternate pricing as much as the base number. Mispricing an additive or deductive alternate, or attaching it to the wrong base scope, can cost a contractor the job or its margin.

Example

The school district received bids on a base gymnasium scope plus three alternates, then accepted the additive alternate for a rooftop solar array only after confirming the combined price stayed within the bond authorization.

Related Terms

Additive AlternateDeductive AlternateBase BidBid Form

Frequently Asked Questions

An additive alternate adds scope and cost to the base bid, such as including a canopy the owner may want. A deductive alternate removes scope and reduces the price, like substituting a cheaper finish. Owners use both to scale a project up or down against budget after seeing competitive base bids.
Public bid laws often require the owner to declare in advance the order alternates will be accepted. Because each accepted alternate adjusts the comparison price, a bidder with a higher base bid but cheaper alternates can become the apparent low bidder once selected alternates are applied. This makes alternate pricing strategically important.
Pricing alternates separately keeps the base bid identical across all bidders, preserving a fair, apples-to-apples comparison. It also lets the owner mix and match optional scope to hit a target budget without reopening bidding. Burying alternate costs in the base bid would defeat both purposes and can make a bid non-responsive.

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