How to Level a Concrete Floor - This Old House

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How to Level an Existing House

Foundations settle over time. Even brand new houses experience some movement of the foundation. The question is, how do you level a floor that sinks toward the center of a home? And how much of this can homeowners do? Of course, this probably isn't something you should attempt on your own with zero experience; however, having an idea of what goes on can help you make the best decisions for yourself and for you home.


  1. Consult a qualified Structural Engineer first.The structure may not be as you expect and you may cause more problems than you solve.
  2. Determine how far the middle of the house needs to be lifted.With a taut string, water or laser level, make a straight line from one side of the foundation to the other. You may find this task easier if you hold the string off the sagging floor joists by attaching blocks of the same thickness at opposite sides of the basement. Nail them to the underside of the joists as near the foundation as you can. Measure the distance from that line to the bottom of the floor joists. Repeat this process in several locations under the house.
  3. When you know where the lowest portion of the center is located, mark that location.
  4. Build a temporary post using concrete blocks or large blocks of wood.Make sure that the post is located on firm, level ground under the house. Alternate the placement of each layer of blocks by 90 degrees to improve stability.
  5. Buy or rent a hydraulic jack.When the space above the temporary post is adequate to place the jack and reach the structural member above, start jacking the house up. As the house moves, add smaller blocks to support the center of the structure at the new elevation.
  6. When the lowest point has been raised to the height of the next lowest points, remove the jack carefully, allowing the house to rest on the temporary post.
  7. Check for problems that may have been created by movement of the house.(See Warnings below.) Sheetrock cracks may appear.
  8. Build another temporary post and repeat the process.
  9. When the floor is level and stable on the temporary posts, it is time to prepare for permanent supports.Existing supports may be usable with minor modifications. Check the bottom of the supports for rot or other signs of trouble. If the bottom of the posts are no longer sinking, they can remain in place. By cutting the center supports shorter, a new beam can be placed on top of the shortened posts to support the center of the house.

Community Q&A

  • Question
    Can I build up my base plate on my kitchen wall foundation without leveling the back of my house first?
    wikiHow Contributor
    Community Answer
    Theoretically you can, but the concept is that if you do one side and the other later, it will put more stress on the un-leveled side. While it is possible, it is best to get the lowest side up higher first, then lift the sides that are more level. If the base plate on your kitchen is the most un-level, you would be fine starting at that point until it is brought up to rough level with the rest of the un-level areas, then proceed leveling all areas slowly.
  • Question
    Where should I begin the process of leveling?
    wikiHow Contributor
    Community Answer
    Start at the highest point of the house, and work your way to the lowest, leveling as you go. Use a water level to determine.
Unanswered Questions
  • What does it mean when the outside wall is not sitting on anything and would it be safe to lower the where the outside wall is setting on the bricks around the house then go back and level the rest?
  • How expensive is it to replace rotting floor beams?
  • How long should it take to do a facelift on all the stringers on a 1300 sq.ft. home?
  • How long can I leave a stabilizer jack post in place in a mud basement with proper footing?
  • Who would I call to give me an estimate on leveling the foundation of my house?
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  • Smaller movements are better than larger movements.
  • Multiple jacks will make the process more convenient.
  • Prior to setting your center jack location be sure the area will be able to handle the load with out settlement. If there are "soft spots" under the jack it may shift and cause some serious problems. Compaction of your jack points will ensure consistent settlement during operation.
  • Drill holes in your steel plates so you can screw them into the beams, to avoid having 10-20 lbs of steel fall on your head when you release the jack after your permanent posts are in place.
  • Many prefer screw jacks to hydraulic because you can get a physical feel for how much resistance you are getting.
  • Give the house time to "settle" after a series of small moves before proceeding to the final position.
  • Wood crushes at 625 lbs psi, but a jack can lift tons. It is critical to use heavy steel plates between the jack and the beams to avoid crushing wood fibers in the beams (destroying their integrity) or worse yet, punching a hole through the floor. The steel plates should be a minimum of .25 inch (0.6 cm) thickness, and large enough to distribute the full load of that jack across the beam.
  • A water level will be as accurate as a transit would be, strings can sag and be hard to get from one side to another underneath house because of structures, plumbing, and ducts.


  • Be aware of water lines in the house. Inspect after each movement.
  • Moving portions of a structure can cause other problems including but not limited to, plumbing leaks, cracked Sheetrock or plaster, roof leaks.
  • Many times some of the doors will not close after the house has been leveled. Use an electric planer on the doors where they rub.
  • Leveling a foundation is a serious undertaking. The more movement required the higher the risk of damage. Be prepared to call a professional especially if small movements cause unexpected, undesirable results.
  • Use of hydraulic jacks can be dangerous. Use proper safety equipment. *Use caution against the peril of heavy objects falling off the jack or the posts.
  • Be aware of gas lines that may be present in the structure. Inspect after each movement.

Things You'll Need

  • Hydraulic or heavy screw jack(s)
  • Steel plates, min.

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Date: 02.12.2018, 23:59 / Views: 32575