How to Straighten Concrete in Front of a Stone Retainer Wall

Wash the concrete and the lower section of the stone wall thoroughly, using concrete cleaner and a scrub brush.

Place 2-inch by 8-inch upright form boards around the open sides of the concrete slab. Situate the tops of the boards at least 1/2 inch from the highest point in the concrete surface. Check for evenness at the tops of the boards with a level. If water runoff is necessary, slope the boards slightly downward and away from the wall. Secure the boards in place with stakes hammered into the ground along the outer edges and by packing soil under and around the boards.

Paint the insides of the form boards with a concrete release agent and mist the concrete to dampen it.

Pour polymer concrete into the form. Seesaw an upright 2-inch by 4-inch board across the tops of opposing form boards, working from the wall out, to screed and roughly level the concrete.

Further smooth the surface of the new concrete by skating it with a bull float, using slightly overlapping motions and going around the stones where the concrete meets the wall as closely as possible. Finish smoothing and leveling the concrete around the stones with a finishing trowel.

Add any desired stamps or textures to the concrete surface, such as a broom-brushed tread.

Run a concrete edger around the perimeter of the new concrete, where it meets the form boards, to create rounded corners.

Cover the concrete with plastic and allow it to cure for at least seven days. Mist the concrete with water regularly during the curing process. Once cured, remove the form boards. Use a chisel to chip away any excess concrete that seeped out from around the ends of the form boards, if they were abutted to irregular stones, or simply hide the seepage by covering it with soil.