How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
Why do cracks sometimes suddenly appear in walls and floors?
Thursday, October 18, 2018
While the crack you just noticed may have been opening slowly over a period of months or years, and it became big enough to catch your eye only recently, it is also possible that it appeared in a single day.
The key word for understanding how a fairly large crack can appear overnight is “elasticity.” While we normally think of things like rubber bands as being elastic, all materials--including concrete, brick and mortar--have a small amount of elasticity. Within that elasticity is the ability to contain the tension (pulling-apart) forces imposed on them—up to a point.
But, like a over-stretched rubber band, when the forces pulling building materials apart exceed a certain point, they “snap” and a crack opens all at once. People in homes with extreme pressure being applied to the structure, from sink hole activity or clay soil heaving, sometimes actually hear the sounds of their walls fracturing. But mostly it’s not that dramatic.
One thing to try to determine after a crack appears in the walls or floor of your home is whether it is a one-time event or will continue to open up. A simple device called a crack monitor can help you determine what is going on. It consists of a plate with a grid printed on it that is placed over the crack and secured at one side, and a clear plastic plate with a cross-hair on it, which aligns exactly with the center of the grid at time of installation, that is secured overlapping it at the other side of the crack.
Keeping tabs on the monitor will tell you if any further movement is occurring and, if so, at what rate. We keep a couple in the truck for installation where a homeowner is concerned about cracks they have found.
Also, see our blog post How do I recognize serious structural problems in a house?
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To learn more about exterior walls and structures, see these other blog posts:
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