The building you’re probably sitting in is moving right under your feet.

You might not notice it, but it’s true. Every building is subject to the forces around it, which is why you see issues like foundation cracks in some older homes—the ground moved the home and the slab cracked under the strain.

The larger the building, the more this movement can affect it. Large commercial buildings are particularly susceptible to the influence of temperature fluctuations, wind, or settling ground. And building materials aren’t usually chosen for their flexibility.

That’s where expansion joints come in.

Expansion joints are a means of allowing a building room to move and shift without causing cracks and problems. When a building is constructed, gaps are left at predetermined intervals to allow for the natural movement that comes from the environment.

But to create an effective outer envelope or shell, you need to make sure the elements don’t come in. That’s what an expansion joint does. Some of these joints are mechanical while others are an expansive material that will move a little to fill the gap if it opens or compact if it closes. You’ve probably seen some of this second kind of joint in long sidewalk runs—they’re the big, thick black chunks of material you see periodically that are slightly thicker than a regular joint.

Expansion joints (also called movement joints) are waterproofed when the building is constructed, but like any construction they’re subject to breakdown over time. Seals need regular inspection to make sure that they’re still able to keep out the elements.

These joints may need replacement eventually, too. Since they’re the point where movement is most likely to occur, they’re also the most likely point of failure. Make sure you’ve set up a plan for your maintenance crew to check them periodically. If they’re not sure what they’re looking for, then call in an expert.

If you run into a problem with the seal or an expansion joint that looks like it’s wearing out, follow the manufacturer’s guidelines to fix, replace, or re-seal the joint. Expansion joints are incredibly important for the overall health of your commercial building. Don’t let them wear out. Take care of them and they’ll take care of you.