How to Fix a Massive Floor Sag

Most floors begin sagging over time as the house settles, floor joists wear out or supports move out of position. Sometimes it's obvious that a floor is really sagging, while other times the sag is less apparent. In either case, a sagging floor can be repaired without the need of a professional if you have the proper patience to work with it over the course of several weeks.

20-ton hydraulic jack
Level

Instructions

- 1
  Determine where the floor is sagging.
- 2
  Repair the sag slowly over several weeks. Push the floor up at 1-inch intervals from underneath in the morning using a hydraulic jack. Repeat the process at noon and in the evening. Check the floor, walls and floor joists to make sure they aren't cracked or damaged each time the floor is raised. Replace or fix any damaged supports.
- 3
  Continue raising the floor at 1-inch intervals until the sagging is gone and the floor is level again.
- 4
  Reinforce the floor when it is in the proper position by installing beams underneath the floor where it was raised.

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