It’s not uncommon to notice hairline cracks in exterior walls—and these cracks don’t always signal more serious foundation problems. However, if there appears to be a zigzag pattern, the cracks are large or the foundation appears to be sticking outward, this is evidence of a greater issue.

A closer examination of the cracks can help you determine if there is cause for concern. For example, vertical cracks often occur from normal settlement whereas horizontal cracks are more worrisome. Other rules of thumb that your foundation should be examined by an expert include if the crack is greater than one quarter of an inch wide, if the crack grows relatively rapidly and if there is any bowing or displacement of foundational blocks.

As with exterior walls, many cracks in interior walls are innocuous. Drywall in particular isn’t the strongest material and can be affected by plumbing leaks, humidity and more—which isn’t necessarily good news, but those concerns can be easier to address than a foundation problem. Alternatively, if the walls are crumbling, bowing or sagging, those are indications that the problem stems from below. Diagonal cracks, cracks that run along the floor or ceiling and peeling wallpaper can also be signs of foundation issues.

Floorboards that sag, squeak or bounce may be a sign of foundation problems—or other issues. At the very least, these concerns warrant inspecting. With finished floors, bouncing can indicate that the foundation has settled or that the structural beams are rotted. With concrete slab floors, such as in a basement or crawl space, be on the lookout for cracks.

Foundation problems can cause your floors and walls to become un-level. Although that can be hard to detect by eye, the issue may be more apparent if you take a closer look at cabinets, and countertops. If these elements were once firmly attached to the walls or level with the ground, but now are separated from the wall or sloping, there may be an issue with your foundation.

Mold or mildew smells in the home are problematic for a number of reasons—and the issues are not always caused by a failing foundation. However, if you notice a persistent mildew smell in your basement or crawl space, that could be due to moisture that seeps through small cracks in the foundation. This can also create a vicious cycle, as moisture can result in further rotting and can attract unwanted pests.

In addition to foundation problems, moisture, weather events and even pests can result in siding issues. When it comes to foundation issues, what you should look for is gaps between planks, growing cracks along exterior walls and space between the siding and window or door frames. These gaps and cracks can also invite in more moisture or pests, which can compound your issues.

Most homes are graded so that rain or melted snow flows away from the foundation. This is for good reason, considering moisture can compromise the integrity of your foundation. If you realize that water is increasingly pooling around the foundation of your home, it could be a simple issue with landscape erosion—or it could signal a bigger problem with the foundation sinking.

If foundation problems cause your house to slope, sink or become otherwise un-level in any places, you may notice that doors don’t shut properly or get stuck. In homes, it’s not uncommon for doors to stick more during some times of year when humidity is higher. But if the problem is greater than a little swelling, you should inspect the part of the foundation in the vicinity below the problematic doors.

If foundation problems cause your home to become un-level, you may begin to notice problems with the plumbing. For example, if your foundation causes any pipes that run throughout the house to back up or be unbalanced, the flow may be restricted. Generally, drainage issues don’t stand alone—so, if you notice this problem, explore your walls, siding, floors and foundation for further signs of a problem.