How To Repair Uneven Concrete Under A Sill Plate

Step 1

Hammer two 10d nails into the opposite ends of one foundation wall. Leave about 1 1/2 inches of the nail sticking up.

Step 2

Tie a string taut between the two nails, and use a transit to level the string as close to the top of the concrete wall as possible without touching it in any spot. A tiny gap of about 1/16 inch is sufficient.

Step 3

Mix water and high-strength mortar mix in a wheelbarrow. Follow the mixing directions on the mortar mix, and stir the wet mortar with a garden hoe or a small shovel.

Step 4

Scoop up the wet mortar with a mason's trowel and deposit it on top of the concrete wall at one side.

Step 5

Step 6

Spread and tamp the wet mortar flat against the concrete until it's level with the string.

Step 7

Continue using the string as the guide and work your way down the wall, adding mortar and leveling it with the mason's trowel as you go.

Step 8

Repeat with the other concrete walls, but leave the original string in place. Just drive a new nail at the end of the next wall and tie a new string between the two nails, pulling it taut and leveling it with the transit each time.

Step 9

Let the mortar dry before removing the nails and setting the sill plate.