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Estimating & Bidding

Substitution

In Plain English

A request to use a different product than what was specified, which requires owner approval.

Definition

A substitution is a request by a contractor to use a product, material, or method different from what is specified in the contract documents. Substitutions require owner and designer approval and must be shown to be equal or better than the specified item. Approved substitutions may reduce cost or improve constructability.

Why It Matters in Bidding

Substitutions are a primary lever estimators use to capture value engineering, hit a budget, or solve a lead-time problem, but they shift approval risk and design liability. A price built on an unapproved substitution is fragile, so estimators must track whether a substitution is a pre-bid request, a contractor option in the specs, or a post-award proposal, because each carries different approval odds and timing.

Example

Facing an eight-week lead time on the specified rooftop unit, the mechanical estimator submits a substitution request for an equal-capacity alternate, noting equivalent performance and a shorter delivery so the schedule and bid price hold.

Related Terms

SpecificationBid DocumentsChange OrderValue Engineering

Frequently Asked Questions

Specs usually set a pre-bid deadline for substitution requests so approved alternates are published by addendum and all bidders price the same basis. Post-award substitutions are riskier because approval is not guaranteed. Estimators carrying a substitution-based price before approval should disclose it or carry the specified product to avoid a non-responsive bid.
An or-equal clause lets a contractor propose a product matching the specified item's salient characteristics. The burden is on the contractor to prove equivalence, and the designer judges it. Estimators should not assume an or-equal is automatically accepted; until approved, the substitution savings remain speculative and should be qualified in the proposal.
The owner, usually acting through the architect or engineer, approves substitutions because they affect design intent, performance, and warranty. Approval is typically documented by addendum before bid or by submittal review after award. Without that written approval, installing a substituted product can trigger rejection, removal, and replacement at the contractor's cost.

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