Grout injection, otherwise referred to as Polyurethane injection grouting, is an effective method for repairing or strengthening masonry walls. This technique involves low-pressure injection of fine hydraulic lime grout into cracks, voids, and cavities within the masonry. This technique increases building resistance to moisture penetration and restores the material continuity across cracks.

Grout injection is especially useful for restoring or stabilizing historic structures because the technique does not alter the building’s appearance. It increases the masonry’s durability and overall service-life by bonding wythes and reducing moisture infiltration.

　　An effective method for repairing or strengthening masonry walls, grout injection involves low-pressure injection of fine cement-based grout into cracks, voids, collar joints, or cavities. Grout injection has several applications: to repair and halt the spread of cracks; to increase a building's resistance to moisture penetration; and to strengthen retrofitted buildings, particularly historic structures and those in seismic areas.

Grout is injected through holes drilled to intercept cracks and internal cavities. Use the smallest-diameter holes possible, drilled into mortar joints, to prevent chipping and damaging masonry units. To prevent damaging while strengthening already fragile masonry units, use a grout pump capable of limiting the pressure to about 8 to 10 psi. For collar joint injection, begin grouting holes at the base of the wall and proceed to the top, moving across the wall horizontally and then upward. Use low lift heights--about 2 feet or less--to prevent wall blowouts. Make sure the project engineer analyzes each situation.

　　Polyurethane Injection Grouting is generally used in Injection Packers of the basement or any tank for making water-resistant or for preventing any leakage. Without Polyurethane Injection Grouting waterproofing work never finished its most important part of the waterproofing process.