Is bridging required by code?

Most codes require blocking or bridging for floor joists with spans over 8 feet, at mid-span intervals. Check your local IRC adoption.

Solid blocking vs. cross-bridging — which is better?

Solid blocking (lumber cut to fit between joists) is generally preferred for its superior lateral support and ease of use as a nail base for pipes and conduit.

Bridging Calculator

Calculate the number of bridging rows required for your floor joist span.

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Enter Your Measurements

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How to Use This Calculator

1Enter the unsupported joist span in feet.
2Click Calculate — bridging is required every 8 feet of span.

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About This Material

Bridging (also called blocking or cross-bridging) is installed between floor joists at mid-span to prevent rotation and lateral movement. It is required for spans over 8 feet.

Installation Tips

•Install solid blocking or metal cross-bridging.
•Stagger blocking for easier nailing access.
•Nail both top and bottom flanges of cross-bridging.

Common Mistakes to Avoid

Installing bridging before subfloor is down — nail the top only, wait until subfloor is on to nail the bottom.
Using undersized blocking for the joist depth.