holes in I-Joists

Ran accross this today. I know holes are usually acceptable, but how about two holes next to each other? I advised my client to check with the manufacturer of the i-joists to see what was permissable. Any other opinioins on this one?

Good advice.

Here is the hole boring guide from G-P’s product

http://www.gp.com/build/DocumentViewer.aspx?repository=BP&elementid=4815 (see page 14)


  1. Hole locations are based on worst case of simple and multiple span
    conditions with uniform floor loads of 40 PSF live load and 10 or 20 PSF dead load,spans from page 3.

  2. Holes not greater than 1.5" in diameter can be placed anywhere in the web, but the hole must be spaced a minimum horizontal clear distance of 2 times its diameter (but not less than 1") from any adjacent hole.

  3. For holes greater than 1.5" diameter, minimum clear distance between
    a) two round holes is 2 times the diameter of the larger hole
    b) a round hole and a rectangular hole is the larger of 2 times the hole
    diameter or twice the rectangular hole width

  4. For multiple holes: The clear distance between the holes must equal or exceed twice the diameter of the largest hole, or twice the longest side of a rectangular hole.

  5. A group of round holes at approximately the same location shall be permitted if they meet the requirements for a single round hole circumscribed around them.

  6. For joists with more than one span, use the longest span to determine hole location in either span.

  7. All holes shown on this chart may be located vertically anywhere within the web; a clear distance of at least 1⁄8"must be maintained from the hole edge to the inner surface of the closest flange.

What I wonder is if that is a bearing point for the joist to the left in the pic. Because of the structural behavior of engineered joists there are restrictions about holes the closer you get to a bearing. Generally, if you are outside that restricted area then the hole can be almost as large as the width of the web. If 2 or more holes fit in that area it’s generally OK. If the holes won’t fit then then next parameter is holes are twice their diameter apart.

But other hole configurations may be just fine. Usually, the material distributor can run a calc on a particular hole configuration to see if it passes muster. Often holes that are outside the published general rules will pass muster just fine.

I imagine there are others but I keep a copy of BC-Calc that lets me run a hole calc if it’s an issue. Also sizing’s for joists and beams. I don’t use it much (maybe once a year) but it’s real useful when I need it. Let’s me call the close ones on whether I specify an engineer or not. (I keep my calcs to myself)