How to Straighten a Sagging Floor Joist

The floor joists in your home hold up the flooring. After several years of abuse from heavy weight, or moisture in a basement, the floor joists may begin to sag. This can cause the floor to start squeaking or bouncing. While extremely bowed floor joists all throughout the floor should be inspected and repaired professionally, joists just beginning to sag can be reinforced with a sister joist. A sister joist is another piece of wood attached to the sagging joist to give it extra strength.

Things You'll Need

• Measuring tape
• Lumber
• Construction adhesive
• Nails
• Hammer

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Instructions

1. • 1

     Measure the length of the sagging floor joist.

   • 2

     Cut one or two pieces of wood the same length as the sagging floor joist. Use lumber that is the same width as the joist.

   • 3

     Apply several S-shaped lines of construction adhesive along one side of the sagging joist.

   • 4

     Lift up the cut pieces of wood and press them against the construction adhesive. Have a partner hold them in place.

   • 5

     Hammer 3 nails vertically along the board every 16 inches to secure it in place.