Adjustable steel columns, also called jack posts or lally columns, can be installed in basements and crawl spaces to support sagging floors or can be used as a fulcrum beneath heavy appliances.

Though originally designed as a temporary solution, adjustable columns are frequently used by homeowners and contractors for more permanent applications.

Step 1: Measure the distance between the floor and the floor joist in need of support. Columns come in various sizes; select one that can adjust slightly larger than the desired height.

Step 2: For applications with dirt floors, it may be necessary to pour a concrete footing. Often a couple of concrete blocks topped with a block of wood to disperse the weight will suffice.

Step 3: Assemble the post in its shortest position. If the post has multiple height adjustment holes, do not insert the height adjustment pins at this time.

Step 4: With the larger portion of the column nearest the floor, position the post atop a wooden block cut from a 1- or 2-inch-thick board.

Step 5: Once the post is in place, raise the top portion of the column and insert any height adjustment pins through the column. At this point, the top plate of the column should be several inches below the sagging floor joist.

Step 6: Insert an additional block of wood between the column’s top plate and the floor joist to disperse the pressure when the post is fully extended.

Step 7: Use an adjustable wrench or manually turn the screw post levers to slowly raise the top plate until it is resting snuggly beneath the floor joist.

Step 8: Make sure the column is vertical, plumb and perfectly centered under the beam.

Step 9: Use an adjustable wrench or manually turn the screw post levers to raise the top plate another quarter of an inch.

Step 10: For sagging floors, continue to raise the top plate of the post one quarter of an inch each day until the floor is level. Never raise a floor joist more than a quarter of an inch on any given day.

Adjustable steel columns are not designed to be the primary means of support. If the column is being used in a lifting type situation, consult a licensed engineer to determine the safe allowable load.

Step 11: Use lag screws or masonry screws to anchor the base plate and top plate into position.