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How to Properly Notch Structural Beams

Ask This Old House plumbing and heating expert Richard Trethewey and general contractor Tom Silva explain how to notch structural beams to host Kevin O’Connor.

Notching structural beams

  1. Avoid “No Man’s Land," the top and bottom of the joist when drilling a hole.
  2. Drill holes no larger than one-third the width of the joist.
  3. For cutting a notch in the top or bottom of a joist, avoid the center one-third of the joist.
  4. The notch may not be bigger than one-sixth the height of the joist.


Joists are available at your local lumberyard.