How to Stiffen Floors for Earthquakes

Seismic retrofitting refers to the process of improving the structural support of a building to help it withstand earthquake tremors. While there is no way to guarantee a building won't be damaged during natural disasters such as earthquakes, the retrofitting process helps make a home safer for when such events occur. While overhauls to the foundation or walls should be done professionally to ensure a safe and proper job, stiffening the floors to better withstand vibration and impact is a feasible do-it-yourself project with the proper materials.

Tape measure
Saw
Wood planks
Hydraulic jack and post
Rag
Construction adhesive
Hammer
Nails
Drill
Lag screws

Instructions

- 1
  Access the joists in your floor through either the basement of the house or a crawl space underneath the floor.
- 2
  Measure the joists with a tape measure. Cut wood planks of equal length and thickness using a saw so they can be attached to the existing joists.
- 3
  Straighten any warped or bending joists by placing a hydraulic jack and post under the affected joist. Jack the joist up by 1/8 inch every 24 hours until the joist is straight. Avoid jacking up the joist more than that because you'll likely damage structures above it that need time to adjust.
- 4
  Wipe down the joists with a damp rag to remove any dirt or dust. Let them dry. Apply construction adhesive to the joists once they are properly straightened.
- 5
  Press the support joist you cut with the saw up against the original and hold it in place for several minutes while the adhesive starts to dry. This is called "sistering" the joist and it adds support to the floor against weight, impact and vibration.
- 6
  Hammer three nails every 16 inches into the two pieces of wood to strengthen their connection. If nails aren't penetrating the wood pieces, drill holes and then insert lag screws to hold the wood together.

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