Mudjacking vs. Polyjacking: Foundation Lifting Methods Compared
Mudjacking and polyjacking are the two primary slab lifting methods used to correct settled concrete in residential and commercial construction. Both techniques inject material beneath a sunken slab to restore grade, but they differ substantially in material composition, hole diameter, curing time, and suitability across soil and load conditions. Contractors, property owners, and structural engineers selecting a lifting method navigate these differences against site-specific soil reports, the age and condition of the existing slab, and applicable local permitting requirements. The Foundation Repair Listings directory provides access to licensed contractors offering both methods across US markets.
Definition and scope
Mudjacking — also called slabjacking or pressure grouting — is a concrete lifting process in which a slurry of Portland cement, water, soil, and occasionally fly ash is pumped through drilled holes into the void space beneath a settled slab. The hydraulic pressure of the injected slurry raises the slab back toward its original elevation. Hole diameters for mudjacking typically range from 1.5 to 2 inches.
Polyjacking — also called polyurethane foam lifting or foam jacking — uses a two-component expanding polyurethane foam injected through holes approximately 0.625 inches (5/8 inch) in diameter. The foam expands on contact with moisture, fills voids, and hardens within 15 to 30 minutes, providing a rigid structural fill.
Both methods fall within the broader category of slab remediation work covered under Chapter 4 of the International Residential Code (IRC), published by the International Code Council (ICC). Local jurisdictions adopting the IRC or International Building Code (IBC) may require permits for slab lifting when the work involves structural elements, public rights-of-way, or accessibility surfaces such as ADA-compliant ramps and walkways. The Americans with Disabilities Act Accessibility Guidelines (ADAAG), administered by the US Access Board, establish maximum cross-slope tolerances of 1:50 for accessible routes, making accurate slab elevation restoration a compliance issue in commercial settings.
How it works
Mudjacking process:
- The contractor surveys the settled slab and identifies void locations using probing rods or ground-penetrating radar.
- Holes of 1.5 to 2 inches are drilled at calculated injection points — typically spaced 2 to 4 feet apart depending on slab size and settlement pattern.
- A slurry mix — commonly 60–70% soil or sand, 20–30% Portland cement, and water — is prepared and pumped under pressure through injection ports.
- The operator monitors slab elevation using a laser level or transit, stopping injection when the target grade is achieved.
- Injection ports are plugged and patched with hydraulic cement or matching concrete mix.
- Full cure of the slurry takes 24 to 72 hours before the surface is returned to service.
Polyjacking process:
- Void mapping follows the same survey methodology as mudjacking.
- Holes of 5/8 inch are drilled at injection points, spaced 2 to 3 feet apart.
- A two-component polyurethane resin (polyol and isocyanate) is injected through a mixing gun; the components react immediately upon contact, expanding 25 to 50 times their liquid volume.
- The operator monitors lift in real time; polyjacking provides measurable elevation within 90 seconds of injection.
- Holes are patched with a cementitious filler or plug.
- The surface is ready for traffic in 15 to 30 minutes.
Polyurethane foam used in structural applications is typically characterized under ASTM International standard ASTM D1621, which covers compressive properties of rigid cellular plastics, and contractors in commercial settings may reference compressive strength ratings of 40 to 100+ psi depending on foam density specification.
Common scenarios
Mudjacking is most frequently applied in:
- Residential driveways and sidewalks with moderate settlement (1 to 3 inches) on clay or sandy loam soils
- Pool decks and patio slabs where cosmetic tolerance is moderate
- Agricultural or rural settings where material cost is the dominant selection criterion
- Slabs over cohesive fill soils where added mass from the slurry does not materially worsen subgrade loading
Polyjacking is the predominant choice in:
- Interior slab lifting where minimal access holes reduce finished floor disruption
- Commercial and industrial floors where 15–30 minute cure time minimizes operational downtime
- Slabs over saturated, weak, or expansive soils where adding the weight of a cement-soil slurry (which can weigh 100–120 pounds per cubic foot) would increase settlement risk
- Proximity to utilities or voids where foam's expansive fill properties are more predictable than slurry flow
- ADA-compliant walkways and ramps where precision lift and fast return-to-service are required
The Foundation Repair Directory Purpose and Scope page outlines how contractors offering these services are classified within the directory by method type and service geography.
Decision boundaries
Choosing between mudjacking and polyjacking involves evaluating five technical dimensions:
| Factor | Mudjacking | Polyjacking |
|---|---|---|
| Injection hole diameter | 1.5–2 inches | 0.625 inch |
| Material unit weight | ~100–120 lb/ft³ | ~2–4 lb/ft³ |
| Cure / return-to-service time | 24–72 hours | 15–30 minutes |
| Relative material cost per lift | Lower | Higher (typically 2–3× slurry cost) |
| Longevity in wet soil conditions | Susceptible to washout | Hydrophobic; resistant to washout |
Weight sensitivity is the most critical variable for sites with weak subgrade. Mudjacking slurry adds substantial dead load beneath the slab. On soils with a bearing capacity below 1,500 pounds per square foot — a threshold frequently cited in residential geotechnical reports — the additional load can accelerate re-settlement. Polyjacking's negligible unit weight (2–4 lb/ft³) does not meaningfully alter subgrade loading.
Slab condition also constrains method selection. Cracked or fragmented slabs with broken panel sections may not transmit hydraulic lifting pressure uniformly; in those cases, slab replacement rather than lifting may be the structurally appropriate outcome, as described in the How to Use This Foundation Repair Resource section covering scope-of-work classification.
Permitting requirements vary by jurisdiction. Structural slab lifting on commercial properties, accessible routes, or public sidewalk panels typically triggers a building permit and may require inspection by a licensed structural engineer of record. The IBC, Section 1705, establishes special inspection requirements for certain soil and foundation conditions (ICC, IBC 2021). Contractors operating in jurisdictions that have adopted the IBC should verify whether the scope of work triggers special inspection obligations before mobilizing.
Safety framing for both methods references OSHA 29 CFR 1926 Subpart P (Excavations) when lifting operations require excavation adjacent to the slab, and OSHA 29 CFR 1926 Subpart Q (Concrete and Masonry Construction) for drilling and pressure injection operations (OSHA Construction Industry Standards, 29 CFR 1926).
References
- International Code Council — International Residential Code (IRC) 2021
- International Code Council — International Building Code (IBC) 2021
- US Access Board — ADA Accessibility Guidelines (ADAAG)
- OSHA 29 CFR 1926 — Construction Industry Standards
- ASTM D1621 — Standard Test Method for Compressive Properties of Rigid Cellular Plastics