Both methods do the same basic thing: pump material under a sunken slab through a small hole until the slab floats back to grade. The difference is what goes through the hole, and that difference is where the trade-offs live.
Mudjacking pumps a cement, sand and soil slurry under the slab. It has been the standard fix for decades, and done well it works. Foam injection uses a two-part polyurethane that expands to a fraction of its liquid volume and sets hard in minutes.
Where each one wins
- Cost: mudjacking usually runs cheaper up front, since the material itself is far less expensive than foam.
- Weight: foam weighs almost nothing once it cures, so it will not compress soft soil the way a heavy slurry can over time.
- Cure time: foam reaches full strength in about fifteen minutes; mudjacking slurry needs real time before it can take a load.
- Hole size: mudjacking holes run about the size of a golf ball; foam holes are closer to a dime.
Mudjacking still wins on very large voids, where the sheer volume of material needed makes foam the pricier option, and on jobs where the budget genuinely will not stretch to foam.
Where foam wins is longevity: it is inert and waterproof, so it does not wash out or feed anything the way a soil-based slurry can in a wet yard over the years. Either way, the right call depends on the size of the void and the soil underneath it, which is exactly what a free inspection is for.