Lifting the Slab

With the concrete cured and the tension applied, the slab was ready for its final process - lifting it six inches off the ground so as to create a void beneath.  Having a space below the slab will prevent any future swelling of the clay ground from creating too much pressure on the slab, cracking it or making it unlevel.

Early on Friday morning, March 29th, a team of workers arrived to do just that - raise the slab.  They went straight to work by removing the rubber plugs placed on top of each screw mechanism.  The plugs kept the concrete out of the hole into which a steel screw was placed.

The hole was cleaned of any debris which might damage the screw or impede the lifting of the slab.  Before the screw was placed into the mechanism, it was coated with a copper based lubricant.

With all 62 screws in place, a large wrench with a T-handle on top was placed into each hole.  Each screw would be turned one revolution in a coordinated way in order to lift that section of the slab exactly 1/3 of an inch.  The workers would move all at the same time upon the direction of the foreman.  They used long pipes to add mechanical advantage.  After turning each row of screws, they would move across the slab to the next row and rotate those screws too.  In total, each screw was turned approximately 18 revolutions in order to raise the slab the desired 6 inches.

T-handled wrenches in place

Ready to be lifted

Awaiting the command to begin

Even the foreman (plaid shirt) took his turn

The effect was apparent almost immediately 

A laser level was used to measure the height of the slab at each screw mechanism before the process and again after it was completed.  They didn't just rely upon turning the screw 18 revolutions; minor adjustments were made as needed to ensure no portion of the slab was too low or too high.  By keeping it level, no internal bending stress was introduced which might cause the concrete to crack.

When everything was competed and the tools were put away, the dirt surrounding the foundation was again mounded up and leveled so as to provide easy access for the next phase - framing the walls and roof.