Joist Spacing and Blocking 101

Joist Spacing and Blocking
Quick Reference Guide
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New joist may be slightly wider
than existing joists, requiring a notch
in the board to align with
the correct height.
New joist may be slightly narrower than
existing joists, requiring an extra shim to raise
to correct height. Recommended to use a
moisture-resistant shim.
Beware of lumber size inconsistencies; it’s
important to properly measure your joist widths
and adjust as needed.
If you are purchasing new joists, measure to ensure they are the same size. If not, you may need
to adjust for slight inconsistencies.
You may need to notch or shim your joist on top of the beam:
When adding or replacing framing to the substructure consider using kiln
dried lumber for best results.
STEP ONE
Check Your Framing Before Laying the First Board