Joist installation - crown up versus crown down

Structure · Joists · printed page 52 (PDF page 53)

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Book index entries

Crown up on Joists Crown up Furnace – Joists Joists

Text in the illustration

crown down
when joists are installed crown down, they can continue to sag under load and could cause localized low spots in the floor system
floor joist
crown up
joists should be installed crown up so that loading will cause them to straighten out

Generated explanation

The illustration compares two orientations of a wood floor joist spanning between supported wall assemblies. The upper drawing shows a joist installed crown down, with a downward bow that can increase under loading and produce localized low spots in the floor. The lower drawing shows the recommended crown-up orientation, with an upward bow that straightens under loading. Dashed outlines indicate the change in joist shape under load, and both assemblies show joist ends supported above concrete foundation walls.