What is an alternate bid in construction?
An alternate bid is a separately priced option on the bid form, an add or a deduct to the base bid, that lets the owner include or remove a defined piece of scope when awarding the contract. An add alternate prices extra scope; a deduct alternate is a credit. Bidders usually must price every alternate or risk disqualification.
An alternate, or bid alternate, is a priced option the owner asks every bidder to include with the base bid. An add alternate is extra scope, like an upgraded roof or a second parking lot. A deduct alternate removes or downgrades scope, like swapping a terrazzo floor for polished concrete. The owner reviews the base bids and alternates, decides what it can afford, and awards a contract made up of the base bid plus the chosen alternates.
Alternates are owner tools for budget control. They let a design team see real market prices for options instead of guessing, and they help a public owner stay inside an approved budget without rebidding.
How alternates show up on a bid form
| Item | Description | Bidder price |
|---|---|---|
| Base bid | Full scope per drawings | $2,140,000 |
| Alternate 1 (add) | Epoxy floor in gym | $48,000 |
| Alternate 2 (add) | Covered walkway to parking | $116,000 |
| Alternate 3 (deduct) | Delete site lighting at north lot | ($37,500) |
If the owner's budget is $2,200,000, it might accept Alternate 1 and Alternate 3, for a contract of $2,150,500, and drop the walkway. Each bidder priced the same options, so the comparison stays fair.
How the low bidder is decided
On public work this matters a lot. The instructions to bidders usually say how alternates affect the award, for example that low bidder is determined on the base bid plus alternates taken in listed order, or that the owner will announce before opening which alternates it intends to accept. Read that section before bid day. A contractor can be low on base and lose the job because its Alternate 2 price was high.
Common alternate pricing mistakes
- Confusing add and deduct. A deduct priced as a positive number, or the reverse, can wreck an otherwise good bid.
- Pricing an alternate in isolation. Alternate 2 might require extra sitework that is only cheap if done with the base scope. State the assumption.
- Leaving an alternate blank. Many bid forms treat that as nonresponsive, or the owner may assume zero.
- Ignoring schedule. An accepted alternate can add weeks. Some forms ask for a time adjustment with each alternate; if not, clarify it.
- Forgetting to get sub pricing for alternates during bid leveling. Subs often skip alternates unless asked directly.
Related terms
Alternates live on the bid form and are often added or changed by addendum. They are different from unit price items, which pay per quantity, and from value engineering, which proposes savings after the bid. See how to build a construction bid that wins for how to structure an estimate around alternates.
Frequently asked questions
What is the difference between an add and a deduct alternate?
An add alternate is extra scope priced on top of the base bid. A deduct alternate is scope removed or reduced, priced as a credit against the base bid.
Can an owner accept an alternate after award?
Sometimes, within a window the bid documents set. Outside that window, adding the scope is usually done by change order at a newly negotiated price.
Are alternates the same as options in residential work?
Similar idea. A homebuilder's option list is a form of alternate pricing, though it is usually not part of a formal competitive bid.
Do I have to price every alternate?
On most formal bids, yes. Read the instructions to bidders; leaving one blank can disqualify the bid.
