What is the minimum bearing required for wood floor joists resting on masonry?

What is the minimum bearing required for wood floor joists resting on masonry?

• A. 1-1/2 inches
• B. 2 inches
• C. 3 inches
• D. 2-1/2 inches

Answer: (C)

End bearing on masonry must be at least three inches. The bearing is the portion of the joist that sits on the wall, and masonry or concrete walls are rigid but can crush or crack under a concentrated load from a joist end. A larger bearing area—three inches—helps distribute the load more evenly into the masonry and provides enough space for hardware or fasteners to secure the joist. This is why three inches is specified for masonry; lighter bearing on masonry isn’t acceptable, even though wood-on-wood bearing can be smaller (around 1-1/2 inches) due to different material behavior.

End bearing on masonry must be at least three inches. The bearing is the portion of the joist that sits on the wall, and masonry or concrete walls are rigid but can crush or crack under a concentrated load from a joist end. A larger bearing area—three inches—helps distribute the load more evenly into the masonry and provides enough space for hardware or fasteners to secure the joist. This is why three inches is specified for masonry; lighter bearing on masonry isn’t acceptable, even though wood-on-wood bearing can be smaller (around 1-1/2 inches) due to different material behavior.