Recommended blocking for engineered wood floors: A few pointers

Blocking, when applied to an engineered floor system, provides lateral support between floor joists and can serve different purposes.  For one, it is designed to prevent floor joists from ‘’rolling over ‘’ from lateral loads or shear, such as in high winds or storms.  Secondly, It can also be used to transfer load from the wall above to the floor below and thirdly it can also provide structural reinforcement in special positioning of floor joists, such as at 45 degree angles.

Make it Full depth

When choosing the wood you’ll use for blocking, be aware that the International Building Code requires that the blocking be full depth, so it’s top and bottom chords are flush with the floor joists’ chords, for better support. A strongback, for example, can’t be used for blocking purposes. 

Choose engineered wood blocking

In a situation where you are using an engineered wood system like Open-Joist Triforce® (or any engineered wood system for that matter), choose an engineered wood and avoid sawn lumber, as it can shrink and jeopardize your blocking support.  We recommend APA rated I-joists, for their reliability and availability through most distributors.

Drilling holes

One last tip, concerning the I-joist, be careful when drilling holes for ducts or wiring: for vertical or a combination of vertical and lateral loads there is very little freedom in the size of hole you can cut. If your require lateral restraint, bigger holes are possible. Whatever their size, the holes will have to be centered horizontally. These rules don’t apply to pre-cut punch holes, which can be used as is. When in doubt, it’s always best to consult with the manufacturer. 

If you have a special situation in which you’re not sure how to apply blocking, don’t hesitate to contact us.

2 Responses

  1. Richard

    Hi Eric,

    “A strongback, for example, can’t be used for blocking purposes. ”

    Strongbacks are usually transverse members that add strength to a system of joists, so wouldn’t lend themselves to being used for blocking. A strongback could be dimensioned lumber or an engineered joist, so I don’t understand what you mean.

    Could you please clarify this for me?

  2. Eric

    Thanks for your comment Richard.
    I am stating that typically we do not specify strongbacks for lateral support over an intermediate bearing wall. We did in the past, but with the code getting more stringent we specify full depth blocking to support both vertical and lateral loads. We do specify strongbacks for lateral support to connect the joists as part of a whole floor system and help reduce vibration. Hope that helps.

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