Plywood Method

• 1). Inspect the floor joists underneath the bouncing floor and look for loose screws. Tighten the screws for the floorboards to see if the loose screws are the problem.
  
  
• 2). Measure the length and width of the floor joist area and multiply the two figures to get the area in square feet. Use this figure to order plywood.
  
  
• 3). Hold the plywood up to the underside of the joists, with the long side of the plywood sheet parallel to the joists; attach the plywood using 1-1/2-inch drywall screws, one every 4 inches. Fit the plywood along the entire floor joist area.
  
  

Bridging method

• 1). Measure the width between the joists. Use the measurement to order metal bridging at the hardware store.
  
  
• 2). Place the metal bridging between the joists so that it forms an x-shape. Place two metal bridges between each set of joists, at the one-third and two-thirds points along the length of the boards. Place another one at the midpoint of each joist if there is not a center brace already installed.
  
  
• 3). Attach the metal bridging, or bracing, using 1-3/8-inch joist hanger nails, two at each end of the brace.