It’s very rare to find a home in Arizona with a basement, and multiple KJZZ listeners asked why through our Q&AZ reporting project.

There’s three main reasons: regulations, soil and cost.

On the East Coast and across the Midwest, builders have to lay foundations 48 or even 72 inches below the surface so the foundation doesn’t crack as the ground freezes in the winter then thaws in the spring.

“If you're going to already be digging that deep, you might as well get some return on your investment by making a basement,” said Philip Horton, an architecture professor at Arizona State University.

Because the ground doesn’t freeze in Phoenix, you only have to dig 18 inches below the surface to pour concrete footing for a house. If you want a basement, you’ll have to go out of your way to dig deeper.

That’s complicated by a common soil phenomena in the state called caliche. Horton said it’s like a naturally occurring cement.

“It’s really hard to dig through and it’s really inconsistent in where it exists in the soil,” he said.

Most developers and contractors in Arizona prioritize quick builds with low costs, so Horton said adding a basement is a risky investment given it’s hard to predict the cost of a dig ahead of time.

If it weren't for these factors, Horton said it would make sense to have basements in Arizona because underground temperatures are lower and more stable.