How and When to Use Floor Jacks for a Sagging Floor

Lead Image
What You'll Need
4-by-8-inch beams
Floor jacks

If you have a sagging floor, you may need to use floor jacks in order to restore any low points and re-level the floor. Using floor jacks to level a sagging floor should be viewed as a temporary solution to your problem. The long-term solution for your sagging floor is to remove the flooring, replace or fix the problems with the foundation that may contribute to the sag, and replace the flooring.

This article will discuss the tools, materials and steps needed to prop up a sagging floor with a floor jack.

Step 1 - Purchase the Beams

You will need to go to a home improvement center or lumberyard in order to purchase several beams. The beams will be hoisted by the jacks to provide the support under the sagging floor. Purchase as many beams as needed, depending on the extent of the sag that is occurring in the floor. You will also need floor jacks that you will placed under the beams. Small sags will only require the use of one floor jack, while large sags will require two or more floor jacks.

Step 2 - Place a Level on the Floor

man reading a level

On the area of the floor where the sag is the most pronounced, place a large level. Check the level as you raise the floor in order to see at what point the sag has been eliminated.

It should be noted that the process of addressing a sagging floor will occur over a period of time, even several weeks if the sag is great. You will need to work on this process over time in order not to cause other structural damage to the flooring or your home.

Step 3 - Place the 4-by-8 on the Floor Jack and Raise

dirty, red floor jack

Underneath the floor, in a crawl space or basement, position the floor jack or jacks and place the beam in position. Carefully hoist the jack until the beam reaches the floor underneath. Continue to raise the jack until you feel some resistance. When this happens, stop hoisting the jack and lock it in place. Check the level to see how much of the sag has been eliminated.

Step 4 - Raise the Floor an Additional Turn

Wait between one and seven days to turn the jack hoist another 1/4 to 1/2 turn. You want to continue this process in the same intervals (one to seven days) until the level has reached the correct the position. Once this happens, you should have eliminated the sag from your floor.