| Scenario | Slab type | Method | Area (sq ft) | Lift (in) | Holes | Regional factor | Estimated cost |
|---|---|---|---|---|---|---|---|
| 1 | Sidewalk | Mudjacking | 120 | 1.0 | 12 | 0.95 | $1,050 |
| 2 | Driveway | Foam | 500 | 1.5 | 30 | 1.00 | $4,160 |
| 3 | Garage floor | Foam | 420 | 2.0 | 28 | 1.10 | $4,980 |
| 4 | Patio | Mudjacking | 260 | 1.25 | 22 | 1.05 | $2,380 |
| 5 | Warehouse | Foam | 900 | 1.0 | 48 | 1.20 | $9,900 |
- Void Volume (cu ft) = Area(sq ft) × (Lift(in) ÷ 12) × Void Factor
- Base Cost = Area × Base Rate(per sq ft)
- Hole Cost = Holes × Per Hole Rate
- Material Cost = Void Volume × Material Rate(per cu ft)
- Direct = (Base + Hole + Material + Add-ons) × (Slab × Access × Soil × Regional)
- Overhead = Direct × Overhead%, Profit = (Direct + Overhead) × Profit%
- Tax = (Direct + Overhead + Profit) × Tax%
- Contingency = (Direct + Overhead + Profit + Tax) × Contingency%
- Total = max(Minimum Charge, Direct + Overhead + Profit + Tax + Contingency)
- Measure the slab section and enter total area in square feet.
- Estimate the average lift height needed across the section.
- Choose the method and enter the planned hole count.
- Set a void factor based on washout and soft spots.
- Add known fees like site prep, crack repair, and mobilization.
- Adjust multipliers and markups to match your local conditions.
- Click Estimate Cost, then export CSV or PDF if needed.
Cost Drivers Behind Slabjacking Estimates
Project cost scales with slab area, average lift height, and the number of injection points. Larger areas increase mobilization efficiency, while higher lifts usually raise material volume. Tight access, heavy-use slabs, and poor subgrade conditions add labor time and raise the crew multiplier significantly.
Material Volume and Void Factor Planning
The calculator converts lift height into feet and multiplies it by area and a void factor to estimate void volume. Use 0.20–0.30 for minor settlement with intact support. Use 0.35–0.55 when erosion, washouts, or pumping indicates hidden cavities and soil loss. If water is present under the slab, assume higher volume and include additional cleanup and sealing allowances.
Method Selection and Rate Sensitivity
Foam injection often has higher unit rates but can deliver fast set times and reduced hole counts. Mudjacking may offer lower material pricing for broad, accessible sections but can require more drilling and heavier equipment staging. If your vendor quotes fixed rates, enter overrides to mirror contract pricing and reduce bidding variance. Review per-hole costs because dense hole patterns can outweigh base area pricing.
Markup, Minimum Charge, and Rounding Controls
Overhead and profit are applied after direct costs, then tax and contingency are added for uncertainty. Small projects commonly trigger a minimum charge that covers setup, travel, and equipment readiness. Contingency is useful when voids are not fully mapped; 5–10% is typical for visible settlement, while 10–15% fits undermined edges. Rounding to 10, 25, or 50 improves bid readability without changing assumptions.
Using the Breakdown to Improve Decisions
Compare scenarios by changing only one variable at a time, such as void factor or access difficulty. The breakdown highlights whether the estimate is dominated by base rates, holes, material, or add-ons. Use the output to justify scope decisions, like adding crack repair after lifting or sealing joints to reduce water intrusion. Export CSV for audit trails and PDF for client-ready summaries.
What information do I need before estimating?
Measure the repair area, note the average lift needed, and count likely injection points. Record access constraints, soil issues, and any required crack repair or sealing. Then choose a method and confirm local pricing assumptions.
How do I choose a void factor?
Start with 0.25 for mild settlement and solid support. Use 0.35 when you suspect gaps under the slab. Use 0.50 or more if washout, pumping, or visible voids suggest significant loss of subgrade.
Why does access difficulty change the total?
Restricted access increases setup time, hose runs, and surface protection. It can also limit equipment placement and slow production, so the multiplier helps reflect added labor and risk without rewriting every unit rate.
When should I use rate overrides?
Use overrides when you have vendor quotes, internal cost data, or negotiated pricing. Overrides let the estimate match real unit rates while keeping the same formulas, add-ons, markups, and scenario comparisons.
Does the estimate include crack repair and sealing?
Only if you enter those add-ons. Slab lifting and stabilization are priced through base, hole, and material components; finishing tasks like crack repair, joint sealing, and cleanup should be added as separate allowances.
How reliable are the exported CSV and PDF files?
Exports capture the last calculated inputs and results stored in your session. CSV is best for auditing and spreadsheets. PDF provides a clean summary for sharing, but you should still verify site conditions and vendor terms.