 It's brick. It was put in in brick. And I thought I just needed to tuck point it. But as I started looking at it, I realized that some of the bricks are actually starting to bow out, and I probably need to fix it. But when I looked into it and started looking into it, the bottom part of the foundation is only a single layer of bricks thick, like from the bottom of the cellar up about four feet. And then they basically made a normal brick wall, two bricks thick, with an interlocking brick and everything. But the bottom part is only single brick.