How to Level a Floor with a Jack
A house settles naturally over time, and a sagging floor is one sign of this. Floor sagging may not be immediately noticeable, but cracks forming in plaster or drywall and doors that do not close indicate that the floor is no longer level. Raising the floor and adding supports to it will eliminate the sag and correct door problems. Screw jacks serve a dual purpose: they raise the floor and act as the support to keep the floor level. Does this Spark an idea?
Things You'll Need
- Tape measure<br /><br />Carpenter's pencil<br /><br />8d nail(s)<br /><br />Claw hammer<br /><br />Concrete support blocks<br /><br />Plumb bob<br /><br />Screw jack(s)<br /><br />4x4-inch pressure-treated lumber<br /><br />Carpenter's square<br /><br />Circular saw<br /><br />4-foot level
Instructions
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1
Measure the distance between the floor joists and the floor of the crawlspace or basement with a tape measure. Mark the lowest point of the sagging floor joist(s) with a carpenter's pencil.
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Drive an 8d nail in the side of the joist, directly above the pencil mark. Leave the head of the nail protruding 1 inch from the side of the joist.
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Place a concrete support block directly below the nail. Tie the string of the plumb bob to the nail so that the tip of the plumb bob is a ½ inch above the concrete support block.
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Align the center of the concrete support block with the tip of the plumb bob to ensure that the block is positioned under the center of the sagging joist. Untie the plumb bob and pull the nail from the floor joist with the claw hammer.
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Set the screw jack in the center of the concrete support block. Measure the distance between the top of the screw jack and the bottom of the floor joist.
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Mark the distance between the top of the screw jack and the bottom of the floor joist with a carpenter's pencil. Extend the mark around the 4x4-inch piece of pressure-treated lumber with the carpenter's square.
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Cut the lumber to length with a circular saw.
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Set one end of the piece of lumber on the top socket of the screw jack. Hold the other end of the lumber against the bottom of the floor joist while you turn the screw jack handle with one hand.
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Hit the screw-jack handle with the head of the claw hammer to tighten the jack and raise the sagging floor.
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Hold the 4-foot level against the bottom of the floor joist. Watch the level carefully as you raise the screw jack, and stop when the floor joist is level.
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Tips & Warnings
When installing more than one screw jack, keep the jacks placed 24 inches apart.
To avoid causing further damage to drywall, plaster or floor tiles, do not jack up your floor more than an ? of an inch a day.
