This past week I needed to create a passageway through an existing foundation for a new sewer line. The foundation is mortared stone with a masonry skim coat. Lacking X-ray vision, I had no way of telling what was below the skim coat until I began removing it. The wall grows steadily wider toward the base and was two feet thick where I needed to push through. The potential existed that the center of my future hole was also the center of a large boulder. I anticipated renting a rotary hammer drill and spoke to two rental yards prior to starting the task. One assured me the tool could break through rock; the other assured me it couldn’t. I’ve pounded enough rock to know that the likelihood of a handheld tool punching a six-inch hole through a two-foot boulder was slim at best. Still, the allure of believing in an easy outcome was overwhelming.

I had dug the sewer line trench with a mini backhoe and had also planned on digging holes for precast concrete piers. Precast piers need to be set at a specific depth. The backhoe was a rental. In hopes of an efficient rental period, I had the concrete piers delivered ahead of the backhoe’s arrival. That was a mistake, fueled in part by the prevalence of material shortages this past year. I didn’t want to rent the equipment and dig the holes only to find that piers weren’t available. Instead, I was faced with the embarrassment and hassle of returning the piers. Concrete piers are a lot of things, but light isn’t one of them.

With the dissatisfaction of poor choreography fresh, I opted for some exploratory foundation pounding prior to renting a heavy-duty rotary hammer. First was layout. I had established the sewer line path and elevation prior to trenching. The pitch of exterior sewer line is 1⁄4" per foot. The distance between the connection point of the new sewer line stub and the house was 28'. This distance is the run. At 1⁄4" per foot there’s a 7" elevation change over the length of run. Using my laser level, I noted the elevation of the top of pipe at the new stub, then translated this elevation to the foundation, allowing for both the elevation change of 7" and adjusting the measurement from top to center of pipe. Using a basement window as a reference point, I transferred the center-of-pipe location to the interior of the foundation wall. I drew a 1' diameter circle centered on the entry and exit points. Using a 1⁄2" hammer drill with a 5⁄8" carbide bit, I drilled a series of holes along the circle’s circumference, creating a breaking line in the surface masonry coat. Slamming away with a two-pound sledge broke the surface coat and exposed the mortared stones. I enlarged the exposed surface as needed to find the edges of the rocks, then used the hammer drill with a carbide bit to remove the mortar. The mortar joints were large. I alternated between drilling mortar, blowing out dust with compressed air, and pounding on the rocks. Eventually I could work a large crowbar in to assist in removing stone. It went quite well, in large part since I was clear of any monstrous boulders. The wall proved to be of doubled boulders. I broke away the exterior layer, then did the same to the interior, never needing to rent the rotary hammer.