Boulder Retaining Wall Downingtown PA The front yard is transformed into a more useful space with the boulder retaining wall which creates a level area ready for a beautiful lawn, garden, or unique outdoor space. Front yard of house is higher and slopes towards house. Preparation for retaining wall includes tree removal. The slope is cut and excavated before placing the retaining wall. Large boulders compose the retaining wall and provide a long lasting and stable wall. Completed boulder retaining wall with new grass started.