The signs worth paying attention to fall into a few categories. Water-related signals include damp walls, efflorescence (the white chalky mineral deposits that appear when water moves through concrete), musty odors, visible mold, and water pooling on the floor after rain. Structural signals are often subtler but more serious: horizontal cracks running along a concrete block wall, diagonal cracks radiating from corners of window or door openings in poured concrete, and any visible inward bowing or tilting of foundation walls. Sticking doors and windows on the first floor can also indicate foundation movement, since frames shift when the foundation does. Northbrook homes built on clay soils are particularly susceptible to lateral pressure and differential settling, so if you’re seeing any of these signs, an evaluation sooner rather than later is the right call.