How to Replace Steel Foundation Jacks With Concrete and Pressure-Treated Wood

Place temporary supports on each side of the jack. Measure over 24 inches to the right and left of the jack, and attach precut 2-by-6 lumber to the support beam of the floor joist to which the floor jack is attached. Stand the lumber upright, and Insert 3-inch screws through the top of the 2-by-6 lumber diagonally and into the wooden floor joist support beam. This will help hold the temporary support in place until you have installed new concrete footers and posts. Remove the foundation jack by backing off the pressure of the screw handle located in the center of the jack.

Find the center of the original location of the steel jack on the floor beam, and drop a plumb bob from this location to locate the center on the ground below. Place a paint mark on the ground in the location that corresponds with the center mark above on the floor joist support beam.

Dig a 24-inch footer for concrete placement. The footer must be 24 by 24 inches wide and long and 12 inches deep to support the floor above. Measure over 12 inches to the left, right, front and center of the original center mark placed on the ground to achieve the outer perimeter of the footing. Dig the footer with a small hand pickax since you may be confined to a tight space beneath a foundation and floor system.

Add Quickrete and water to a wheelbarrow, combining the ingredients with a hoe. The texture of your concrete mixture should be consistent with pancake batter. Place the concrete into a 5-gallon bucket and pour the mixture into the footer hole. Smooth off the concrete with a hand trowel. Allow the concrete to set for 24 hours before placing any weight on the footer.

Measure and cut a 6-by-6 treated post to be placed between the bottom of the support beam of the floor joist system where the old, steel support posts rested. Insert the post in place, and attach the post to the bottom of the floor joist support beam where the steel post rested. Insert 3-inch wood screws through the top of the post at an angle and into the bottom of the floor support joist, placing one screw on each side of a four-sided post. Plumb the post using a level, and tap the bottom of the post until it rests plumb on the newly poured concrete.

Install L-brackets on each side of the four-sided 6-by-6 post. Attach the L-bracket to the side of the post using 3-inch wood screws. Drill through the bracket where it meets the concrete using a hammer drill. Insert concrete screws through the bracket and into the concrete to secure the post in place.