How to Fix a Slab Leak in a Garage

Dig around the perimeter of your garage with a shovel. Make the sloped trench 12 inches deeper than the floor of the garage, at the highest point in the yard, and 18 inches deeper at the lowest point. Discard any rocks from the excavation and save the dirt.

Add a 4-inch bed of gravel in the bottom of your trench. Lay a french drain into the trench with the slotted side facing up. Place the end of the french drain at the lowest point of the trench. Cover the drain with gravel. Put the soil from the original excavation back into the trench.

Chip away the edges of any damaged areas with a cold chisel. Place the blade of the chisel against the side of the crack and hit its handle with a sledgehammer to chip away the loose edges. Repeat this process around the entire perimeter of every cracked area of the garage slab. Clean the area with your shop vac.

Sweep the entire garage with a push broom to remove all dirt, dust and debris from the floor. Mop the floor with clean water and let it dry completely before continuing.

Mix your hydraulic cement as per the manufacturer's instructions. Fill each crack with the mixture. Push the cement into every crack with the tip of the blade of your trowel. Scrape the side of the blade of your trowel across each crack to remove any excess cement. Let it cure for 72 hours before using the garage.