The oldest portion of the building has no foundation. We’re remedying that by pouring one underneath the existing walls. To do this, sections are excavated and a footer is poured down to a depth of 1.2 meters or more. The sections are joined by rebar.
After the footer is poured, there remains a gap between it and the wall. That has to be filled by first cutting and hammering pieces of brick to fit the gap tightly: mortar will recede and leave a gap, but brick will not. After the bricks are hammered into place they are mortared to hold them.