The hole chart on page 9 of the TJI® Specifiers Guide show the allowable locations for various size holes based on joist depth and spacing for uniformly loaded joists. This chart allows holes 1 ½” and smaller to be drilled anywhere in the web outside of the hatched zone. All holes larger than 1 ½” must be spaced at least 12” from the edge of the hole to the inside face of bearing.
Although cutting holes larger than 1½” in TJI® joist webs near end bearings is not permitted in the table, we recognize that this condition does arise. Technical Bulletin TB-817 provides a possible repair for round holes within 12” of the face of an end bearing. The applicability of this repair is based on hole size, joist properties, load and on center spacing. The maximum allowable hole is 6 ½” diameter in a 16” deep TJI® joist.
For joists that are not uniformly loaded or otherwise do not fit the parameters of the Technical Bulletin, please contact Weyerhaeuser Technical Support.