What are the requirements for locations of diagonal knee braces?

Knee braces should only be installed at corner posts. Interior posts should not have knee braces. Diagonal bracing can contribute to the stiffness of the deck and, therefore, cause additional lateral loads on the posts. Since center posts receive more vertical load than corner posts, additional lateral load can cause overstress. For this reason, DCA6 does not show the use of diagonal bracing on center posts.

This FAQ is based on the presentation of BCD303 – Design for Code Acceptance No. 6 – Prescriptive Residential Deck Construction Guide.

Also, see Page 12 of Part II: Design Values for Structural Members for background on the Wet Service Factor.