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How to Use Concrete Lifting Rigs to Raise Sinking Slabs

It’s estimated by the EPA’s Energy Star program that properly sealing cracks and installing quality insulation can decrease monthly energy bills by up to 20%. But did you know that some insulation problems can be caused by sinking concrete?

Concrete lifting rigs are used for foam jacking — a method of repairing sinking concrete by injecting high-density polyurethane spray foam underneath the slab causing it to rise back to the desired height. Sinking concrete can lead to a myriad of problems, including gaps that can compromise the insulation of a space. If you’re struggling with sinking concrete, slab lifting is a solution you should consider. When performed correctly, there should be no sign of the foam underneath, and the slab should stay level for years.

How to Use Concrete Lifting Rigs

  • Locate the Sinking Point
    Firstly, locate the place where the sinking is occurring. You can determine this by using a carpenter’s level and moving it along the slab until it begins to turn downwards towards the sinking point. Mark this area and then place another mark where the lowest point is located. Depending on how large the slab is, you can place additional marks every six inches beginning at the lowest point and extending to the most level area.
  • Drill the Holes
    Secondly, drill holes down from each marked point using a masonry bit of 5/8 inches. Be sure to slowly drill the holes to prevent cracking the slab, and remove any dust from the holes with a shop vac. (Keep some of the dust to be used later.)
  • Insert the Spray Foam Equipment
    Insert the hose from your concrete lifting rigs beginning at the highest point. Be sure that the hose goes down the hole far enough, without actually pushing against the soil underneath. Once done add your high-density polyurethane mixture to the spray foam rig hopper.
  • Lift the Slab
    Before you begin pumping in the mixture, place your carpenter’s level next to the entry point to ensure proper leveling. Start your concrete lifting rig and begin injecting the mixture under the slab. Monitor it carefully as it rises, and watch for changes in the sloping of the concrete as it fills. Once at an adequate level, stop pumping and remove your hose.
  • Rinse and Repeat
    Continue this process for each hole that you’ve created, raising the slab until all parts are lifted equally.
  • Cover the Holes
    Using some of the concrete dust from earlier, mix together a batch of fast-setting concrete. The dust from earlier will help the tint the new concrete to match the color of your slab. Fill the holes by placing the new concrete mix into a grout back and injecting it into the hole. Fill each until they are level and smooth as needed. Allow everything to set for around 48 hours before conducting any further work or adding any substantial pressure.

Concrete lifting rigs are perfect for raising sinking concrete slabs that might be causing issues in or around your home. While it might seem more like an aesthetic issue, sinking concrete can cause foundational damage and problems with insulation if not fixed properly.

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