Skip to main content
Back to Glossary
Acronymsaka: Basis of Design

BOD (Basis of Design)

In Plain English

A document explaining why design decisions were made and what criteria the building systems must meet.

Definition

The Basis of Design is a document that describes the design intent, criteria, assumptions, and system selections made by the design team to meet the owner's project requirements. It explains why specific systems, equipment, or materials were chosen and establishes the design parameters against which the completed project will be evaluated during commissioning. The BOD is a core component of the commissioning process and is typically developed by the engineer of record.

Why It Matters in Bidding

The Basis of Design tells estimators why systems were selected and the performance criteria they must meet, which clarifies scope ambiguities that drawings alone leave open and helps avoid pricing the wrong equipment. On design-build and commissioned projects, the BOD also frames the contractor's responsibility, so misreading it can lead to substituted equipment that fails commissioning and triggers costly rework.

Example

While bidding a lab fit-out, the mechanical estimator reads the BOD's redundancy and air-change criteria and realizes the project needs a backup air handler that the floor plans did not obviously show, adjusting the equipment quote accordingly.

Related Terms

ASHRAEMEP (Mechanical, Electrical, Plumbing)RFI (Request for Information)

Frequently Asked Questions

It reveals the performance targets and system selections behind the drawings, exposing requirements like redundancy, efficiency, or capacity that drive equipment cost. Estimators use it to confirm scope, justify substitutions, and avoid pricing undersized systems. Reading the BOD early reduces the risk of bidding equipment that later fails to meet the owner's documented criteria.
The owner's project requirements state the owner's goals and expectations in their terms, while the Basis of Design is the design team's technical response explaining how those goals will be met. The OPR sets the targets; the BOD documents the engineering decisions and criteria used to hit them, and commissioning verifies the result against both.
Its status varies by project. The BOD often accompanies the construction documents to convey design intent and commissioning criteria, but it may not carry the same contractual weight as the drawings and specifications. Estimators should check the bid documents to see whether the BOD governs scope or serves only as informational background.

Need more than definitions?

Get AI-powered bid alerts, automated form filling, and proposal drafting.

Start Free Trial

© 2026 ConstructionBids.ai — A LaderaLabs Product