How to Stiffen Wood Floor Joists

Cross bridging, otherwise known as herringbone bridging, are 1-by-3- or 2-by-2-foot pieces of lumber that are trimmed down to fit between each set of floor joist at an angle. The wedged boards will tie in each joist to the next to stiffen and distribute weight throughout the entire floor. When the cross bridging is complete, there will be an "X" between each set of floor joist with the cut strips of wood. This will evenly distribute the upper and lower ends of the joist across the entire floor.

Tape measure
1-by-3-foot lumber
Pencil
Carpenter’s square
Circular saw
8d nails
Hammer
Safety glasses

Instructions

- 1
  Place the end of the tape measure an inch below the upper edge of the floor joist. Stretch the tape at an angle down to the next parallel joists an inch from lower edge. Look at the tape measurement for the cross bridge length and transfer it to the 1-by-3-foot piece of lumber.
- 2
  Scribe a straight line across the face of the lumber at the cross bridge measurement using a carpenter’s square. Cut the lumber across the line using a circular saw.
- 3
  Angle the cross bridge member between the two parallel joists with one end in the upper corner and the other near the lower edge. Secure the upper end of the cross bridge directly to the joist with a pair of 8d nails.
- 4
  Push the lower end of the cross bridge member against the opposite joist so it is wedged into place. Hammer a pair of 8d nails through the lower end of the cross bridge member and into the joist to secure it into place.
- 5
  Continue down the entire span of floor joist making sure every cross bridge member is wedged in the same direction. Reverse direction when the first course of cross bridge members are installed. Install the next course of cross bridge members with the upper end opposite of the first to form an "X" between each set of joist.

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