S. Altan Atasoy, Civil Engineer
October 1, 2026

Concrete Foundation Crack Repair in Gaithersburg, MD | Polyurethane Injection Case

A vertical crack and dark staining on a poured-concrete basement wall called for a focused repair at a Gaithersburg, Maryland home. The affected area was partly hidden behind foil-faced insulation and fiberglass, so the crew first opened the covering to reach the concrete. This was a localized interior foundation crack repair—not a French drain or a whole-basement waterproofing installation.

Foil-faced insulation opened to expose a poured-concrete basement wall before crack injection in Gaithersburg, MD — The basement wall before the work area was fully exposed.

Finding the repair area behind the insulation

Once the wall was exposed, a vertical crack and dark streaks were visible above the floor. The crew marked the section to be repaired. Access to the actual concrete mattered: a surface patch over the insulation would not have treated the crack inside the wall.

Exposed vertical crack with injection packers and staining on a poured-concrete basement wall in Gaithersburg, MD — With the insulation opened, the vertical crack and injection points are visible.

Polyurethane grout injection and surface finishing

The completed work scope called for holes drilled along the crack, injection packers, and low-pressure polyurethane grout to fill the crack and its water path. After the injection, the packers were cut off, excess material was removed, and the exposed wall was patched with cementitious mortar.

The distinction is important: the gray finish visible in the final photo is the restored wall surface. The polyurethane injection is the step intended to seal the crack within the concrete. The team completed this targeted repair over two site visits in June 2026.

Cementitious mortar finish over the repaired concrete foundation crack in a Gaithersburg basement — The repaired section after cementitious surface finishing.

Questions about concrete foundation crack injection

Can a foundation crack be repaired from inside a basement?

Some cracks in poured-concrete walls can be treated from the interior, as this project was. The right approach depends on the wall material, crack condition and water source. The same method should not automatically be applied to a brick or hollow-block wall.

How does polyurethane grout injection work?

Injection packers create controlled access to the crack. Polyurethane grout is introduced under pressure so it can move into the crack and help seal the water path. The ports are then removed or cut back, and the surface is finished.

Is crack injection the same as installing a sump pump?

No. This job addressed a localized crack in a concrete wall. It did not include a perimeter floor trench, interior drain tile or a sump pump. Those systems address different water paths and should follow a separate diagnosis.