Basis of Design and Substitutions Simplified

When it comes to specifying building materials and products, architects use various methods to communicate their design intent. One such method is using the term “Basis of Design” when specifying a product in a 3-Part Specification.

This is a quick review of the Basis of Design usage, substitutions in accordance with Division 01 and when substitutions are not permitted is used.

3-Part Specification Text

  • “Basis-of-Design” followed by a manufacturer’s name, product name, model number, and any relevant performance criteria.
  • It serves as a clear reference point for contractors and suppliers, ensuring that everyone involved understands the product that setting the standard for the project.
  • The term is often followed by Substitutions options:
    • In accordance with Division 01.
    • Not Permitted.

In Accordance with Division 01:

Division 01 of the project specifications covers general requirements, including administrative and procedural matters. Where a Basis of Design products are specified, Division 01 may allow for product substitutions when certain criteria are met. When the proposed substitution is of equal or better quality and performance compared to the specified product, a substitution may be accepted.

Division 01 sets the framework for how the project is executed. And it outlines the rules and procedures for managing substitutions. It is a critical part of the contract documents that govern the entire project.

Basis of Design 3-part specification
Example of Division 01 Requirements

Example of Division 01 Requirements.

Product Substitutions Not Permitted

There are situations where architects specify that product substitutions are not permitted. When there are specific legal or safety requirements that mandate the use of a particular product. Or when the architect or owner has a strong preference for a specific item.

When product substitutions are not allowed. It means that the specified product or material in the Basis of Design 3-Part Specification must be used without deviation.

This approach ensures that there is no compromise in meeting project requirements. Especially when specific certifications, warranties, or compliance standards must be upheld.


The phrase “Basis of Design” is just another way for building product manufacturers’, architects and specifiers to say, “this product, Or Equal.” Unless Division 01 makes it clear what is considered an essential criteria, the Contractor has wide discretion to offer substitutions.