Things You'll Need
Flashlight or lantern
1-ton hydraulic jack
12-inch by 12-inch by ¾-inch plywood block
4-inch by 4-inch post material
For more a more extreme sagging of several inches, keep the distance the girder is raised at any single pier post to 1- to 2-inch increments to minimize stress on the girder. Raise one point and then move to another and repeat until the girder has been leveled. The idea is to slowly raise the entire floor structure to level where the depression exists and this is accomplished most effectively in a gradual manner.
Exercise caution in using the hydraulic jack to ensure that it is on a stable base and kept as vertical as possible. This will provide safe support for the beams as they are raised and posts are replaced.
A pier and beam house foundation essentially elevates the house above the ground to provide a level platform based on specifically positioned footings. These footings support wood beams carrying the floor structure and walls above. As a home ages, many factors can contribute to the "sagging" of interior floor areas, such as the natural ground settling at random pier locations. You can level an area of floor using the crawlspace beneath the house.
Establish the area of floor to be leveled and position yourself in the crawlspace beneath that point with a light source, builders level, hydraulic jack, hammer, nylon string, nails and plywood block.
Attach a level string line on the sagging girder beam by tacking a nail diagonally into the lower corner of the beam at two points as near to the ends as possible or, at a minimum, spanning the depressed floor area. Tie a piece of nylon string between the two nails, keeping it taut and positioned visually level with the lower edge of the beam. This string line will define the amount of sag along the length of the girder beam. String lines should be placed on any girder lines that are in the area of the floor to be raised.
Position the hydraulic jack on the plywood block on a flat surface beneath the approximate mid-point of the girder beam to be leveled, next to the nearest pier.
Measure the vertical distance between the string line and the top of each pier block. Ensure that the string line is free and tight. Cut a piece of 4-inch by 4-inch post to replace any existing pier post that that is more that ½-inch shorter than the level string line. New posts are not mandated for a beam sag of ½-inch or less and can be shimmed or blocked between the girder and post.
Use the hydraulic jack set up in Step 5 to raise the girder and remove the existing post or insert the necessary shims to fill the gap. For post replacement, insert the new post in place and lower the girder down to rest on the top of the post. Secure the new post in place with nails diagonally through the side of the girder into the top of the post and at the base of the post into the pier block.
Repeat Steps 3 through 5 at each pier post location that requires leveling according to the string lines. When completed, use a builder's level to check each section of girder to verify level.
Paul Massey has been writing since 2009, drawing on a 35-year career in the construction industry. His experience includes 15 years as a general building contractor specializing in architectural design, custom homes, commercial development and historic renovations.