The Capacity of a House-Leveling Jack

Types

• House jacks are surprisingly small if you consider the weights they lift. A miniature bottle jack may be no taller than 6 inches, while other bottle jacks may range up to 2 feet in height. Bottle jacks, named for their tall, cylindrical shape and narrow necks, have a handle mounted on one side. A screw jack looks like a musical horn stood on end, with a screw coming out of the top, or the mouthpiece of the horn; the large industrial screw raises or lowers the jack height.

  Different jacks fulfill different purposes. Bottle jacks, for example, lift quickly but slip as they hold; screw jacks come into play after a lift to hold a wall or other house part in place. Airbag jacks are pillow-shaped balloons of neoprene that lift as they inflate. Air bags excel in short lifts in tight places; they lose strength as they inflate.

Ratings

• The strength of a house-leveling jack is measured according to how many tons it can lift under ideal conditions. Mini bottle jacks rated for 1 or 2 tons have the strength to straighten sagging door or window frames. A 15- or 20-ton jack might provide lift for a sagging beam while a new post is installed or replace a beam that must be moved in a supporting wall. Several 60-ton bottle jacks followed by 30-ton screw jacks might lift a house to replace a rotted sill or replace a foundation.

Systems

• Lifting a whole house to move or replace a foundation calls for a system of 15- to 20-ton cylindrical jacking devices called rams, installed in heavy bases and connected to a manifold with one gauge for each ram. A hydraulic pump raises all of the rams at the same time. Raising a house is a delicate procedure that puts stress on all of the joints and corners, so gauges allow ram adjustment as the house is raised and moved.

Considerations

• Although straightening a door or window frame is a project that the average homeowner can undertake with success, raising a wall or an entire house is a project best left to professionals or to be attempted only with professional supervision. Always choose a house-leveling jack with more capacity than necessary, and extend jacks with stout 4-by-4-inch or 8-by-8-inch dimensional wood lumber or similar laminated veneer lumber (LVL). Rams and other jacks used to raise walls or houses should sit on bases of LVL or other hardened, moisture-proof material to keep the jacks from sinking into the ground.