Lift slabs safely and size grout with precision. Account for voids, waste, and density quickly. See results instantly, then export to CSV or PDF.
| Scenario | Length | Width | Lift | Void factor | Overage | Adjusted volume |
|---|---|---|---|---|---|---|
| Walkway panel | 6.00 m | 2.00 m | 20 mm | 0.90 | 10% | 0.238 m3 |
| Garage bay | 5.50 m | 4.50 m | 25 mm | 0.85 | 12% | 0.590 m3 |
| Patio slab | 18.0 ft | 12.0 ft | 1.0 in | 0.90 | 10% | 17.82 ft3 |
Base void volume estimates the cavity created by lifting the slab.
Adjusted grout volume includes a practical overage.
Grout mass uses the selected density.
Lift height is the average vertical rise created under the slab footprint. Measure at several points near corners and mid spans, then average the readings. Using a single maximum value often overstates grout demand. When the slab is warped, use a grid of measurements and average only the zones being injected.
The void factor adjusts for incomplete contact and irregular cavities. A value near 1.00 assumes a uniform gap, while 0.70 to 0.90 reflects uneven support and partial filling. Start conservative, then refine after observing take rates at the first injection ports. Document the factor used for repeatable estimating. If soil is pumping or fines wash out, expect higher take and consider staged lifts.
Overage covers mixing losses, hose priming, spillage, and grout left in the pump. For small jobs, 10 to 15 percent is common. For long hose runs, high temperature work, or frequent stops, increase overage. If prebagged grout is used, round bags up to avoid interruptions during lifts. Track return waste and leftover material to tune future overage rather than guessing.
Grout density and bag yield depend on product type, water ratio, and entrained air. Use supplier data or batch tests for better accuracy. The calculator converts volume into mass and bags by dividing adjusted volume by yield. If the project specifies minimum strength, do not add extra water to chase yield. Consider temperature and mixing time, because both can change flow and apparent yield in the field.
Volume is a planning number, not a pressure target. Confirm the injection plan, port spacing, and maximum uplift per cycle. Monitor lift with a level, stop when target elevation is reached, and allow for redistribution. Compare planned volume to actual take to improve future estimates and reduce overruns. Record final elevation, injected volume per port, and any refusal points to support quality reporting.
Enter the average lift height across the area you will inject. Take multiple measurements, average them, and use that value. If only part of the slab is lifted, estimate that zone separately.
Real voids are rarely uniform. The void factor reduces the idealized volume to reflect uneven cavities and incomplete contact. It helps prevent ordering too much grout while still planning for realistic take.
Use 10% for typical jobs with short hose runs and steady pumping. Increase to 15–20% when priming losses, long lines, or stop‑start pumping are expected. Track actual waste to refine future jobs.
It is an estimate based on bag yield. Yield changes with water ratio, mixing energy, and product type. For critical work, run a small batch test and update the yield value in the calculator.
This tool is built for grout volume planning and density-based mass estimates. Foam behaves differently and expands. Use manufacturer expansion ratios and a foam-specific estimator if polyurethane is the specified material.
Pump time helps plan crew duration and equipment scheduling. It uses adjusted volume and the pump rate you enter. Actual time may vary due to setup, port changes, and pauses during controlled lifting.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.