Polyurethane foam is the most common material for residential and commercial void filling because of its water-resistance, lightweight properties, and fast cure time. For very large voids in heavy industrial or municipal applications cementitious grout is sometimes used for its higher compressive strength and lower material cost per cubic foot. Scaldino selects the fill material based on void size, expected load, and site conditions.

A slab that is sunken typically has both settlement and voids and the settlement is the visible symptom and the void is the cause. A slab that is still at grade but flexes underfoot, sounds hollow when tapped, or has cracked without visible settlement likely has a void without having yet settled. Scaldino's assessment distinguishes between the two conditions and determines whether the repair is filling only, lifting only, or both.

Yes. If the slab is at the correct elevation but has lost soil support beneath it void filling stabilizes the slab without any vertical movement. The foam is injected at low pressure to fill the void without generating upward force on the slab. This is the approach used when a slab is level but hollow or when lifting would cause the slab to exceed its target elevation.

An unfilled void leaves the slab unsupported over the hollow area. Every load applied to the slab is transferred across the void as a beam rather than distributed across supported soil. Over time this causes the slab to crack and eventually collapse into the void. Void filling is a proactive repair that prevents this failure mode before visible settlement or cracking occurs.

The most common field method is the tap test and striking the slab with a hammer and listening for the hollow sound that indicates a void beneath. Ground-penetrating radar provides a more precise map of void extent and depth for large commercial slabs or where the void boundary is uncertain. Scaldino uses both methods to characterize the void fully before specifying the fill volume.

Voids form when soil beneath a slab erodes, washes away, or consolidates under load. Water is the primary cause and it enters through slab cracks and joints, carries fine soil particles with it as it drains away, and leaves an empty space behind. Poor compaction of fill soil at the time of construction is the underlying condition that makes most slabs vulnerable to void formation.

Concrete patching fills surface defects and cracks, spalls, pitting, or missing sections and with repair mortar or polymer compound. Leveling addresses structural settlement by lifting the entire slab back to grade. A surface that is both settled and deteriorated may require leveling first followed by patching to achieve a structurally sound and cosmetically repaired result.

Concrete void filling injects polyurethane foam or grout beneath a slab to fill hollow spaces that have formed due to soil erosion or washout. Voids are common under driveways, garage floors, and basement slabs. Left untreated, voids cause the slab to flex and crack under load and filling them stabilizes the surface before collapse occurs.

Concrete leveling typically costs 50 to 75 percent less than full replacement by eliminating demolition, disposal, new pours, and extended curing time. For slabs that are structurally sound but have settled, leveling is almost always the more cost-effective solution. Replacement is only warranted when the concrete itself has deteriorated beyond repair.

Most residential concrete leveling jobs are completed in one to three hours depending on the number of slabs and severity of settlement. Polyurethane foam injection cures in 15 minutes, allowing same-day use. Mudjacking requires 24 to 48 hours before the area can be driven on.