Frost depth dictates the foundation. Chicago frost penetrates deep, and anything built on a footing above that depth will be lifted and dropped by frost heave every winter until it cracks. This is the single most common reason new garden walls, steps and porch piers fail within a few years. They were built on inadequate footings by someone who did not account for how deep the frost goes here.

Freeze thaw punishes the wrong materials. Water absorbed into mortar or brick freezes, expands roughly nine percent, and pushes. Dozens of times a winter, every winter. Brick has to be rated for severe weathering exposure, and mortar has to be specified for the job rather than mixed to whatever is convenient. Get either wrong and the wall spalls within a decade.

Mortar has to match the brick, not exceed it. Mortar should be softer than the masonry around it so it absorbs movement sacrificially. Using high strength Portland cement mortar with softer brick, particularly when tying into older Chicago masonry, forces the failure into the brick faces instead of the joints. It is a common mistake and it is not reversible.

Clay soil moves whatever you build on it. Glacial clay swells when saturated and shrinks as it dries, and it does so with enough force to move footings. New masonry needs proper footings, drainage and expansion joints, or the seasonal movement simply cracks it.

Water has to have a way out. Masonry is not waterproof and it is not supposed to be. It absorbs moisture and releases it. A wall built without weeps, flashing or a drainage plane traps water inside, and in a Chicago winter trapped water becomes ice inside the wall.

Road salt attacks anything at ground level. Steps, stoops and walkways take de icing salt every winter, which scales concrete surfaces and corrodes reinforcement. Material selection at ground level matters more here than people expect.