Precision Lift® for soil stabilization and slab lifting
Client: Homeowner
Contractor: Olshan - Nashville
Challenge: A home in metro Nashville was under renovation to be resold. It had a 24’ x 24’ enclosed garage with concrete slab. One corner of the garage slab has settled 6” below original grade due to a void under the slab (approximately 1 foot). There is also a set of steps in the settled area which lead to the entrance from the garage. The steps were no longer safe to use due to the nearly 13” distance between the door sill and the top step.
The settlement was caused by a void that formed under the slab due to an improperly placed downspout adjacent to the
garage. The downspout directed water under the foundation causing erosion which over time lead to the void and settlement of the slab.
✓ Fill the void and cut off the path for further water intrusion.
✓ Lift and level the slab back to its normal position
Injecting structural polyurethane foam into the voids beneath concrete slabs can stabilize them without excavation or the added weight of cement, which can aggravate an existing soil settlement issue.
Our Precision Lift® products are polyurethane foams that lift and support slabs, stairs, footings, or foundations, putting them back to their original position.
Solution Plan:
The crew used the Precision Lift® slab lifting system from Prime Resins to inject Precision Lift 4.0 structural lifting foam to fill the void and raise the slab back to original position. The compact Revolution Slab Lifting Machine is a turnkey unit designed to be transported easily into congested project locations or anywhere trailer or truck mounted rigs can t reach.
The Revolution has built in material hoppers, onboard heaters, heated hoses and is powered by standard 110-volt power source. Its proprietary Equalizer Impingement Gun is the first designed exclusively for slab jacking applications and greatly reduces down time.
1. Design & Execution:
The Revolution Pump was quickly unloaded and set for production. Five 3/8” injection holes were drilled around the perimeter of the garage in the area of settlement.
2. Drilling Holes:
The holes were drilled approximately 3 feet from the edge of the slab and 4 feet apart.
The distance from the edge is to help prevent lifting foam from coming up into the perimeter joint during expansion potentially causing a binding point.
3. Hole Placement:
The holes where spaced strategically to fill the void under the slab and spread hydraulic lift created by the expanding structural foam.
As in many residential garages, the perimeter of the garage slab was framed on three sides by CMU foundation walls. It is common for slabs in this configuration to bind or have restrictions from aggregate, rebar or other debris that falls into the joint during settlement. These pinch points must be eliminated to successfully raise the slab. In many cases, dropping a weight like a sledgehammer on a solid block of wood near the suspect restriction will cause enough vibration to shear the edges of the offending obstruction and allow the lift to continue. If needed, sawing the joint between the wall and the slab with a concrete saw or even a Sawzall-type blade may free up the slab.
The crew began injection at the corner, which was also the lowest point of the settlement. A dial indicator was set up to monitor the slab movement. Over the next two hours, the crew moved between the five injection sites.
Sites that were previously injected had to be redrilled each time to create a new fluid path once foam is cured beneath the slab. Minor binding issues were encountered and remedied by tapping the sledgehammer technique method mentioned previously. Over the course of the next two hours the slab was raised to its original elevation along with the steps, which could again be used to enter the house.
The customer (home owner) was very pleased with the outcome and said it would most definately increase the value of the home. Further, he said that settled concrete lead potential buyers to become weary thinking there may be foundation issues.
This successful project wliminated that condition from this property which in the least will make selling easier.
