U.S. single-family home prices rose in June, though the pace of gains slowed slightly, a closely watched survey showed on Tuesday.

The S&P/Case Shiller composite index of 20 metropolitan areas rose 0.9 percent on a seasonally adjusted basis. Prices rose 1 percent in May.

On a nonadjusted basis, prices rose 2.2 percent.

Compared to a year earlier, prices were up 12.1 percent, in line with economists’ expectations. Prices were up 12.2 percent in the year to May, the biggest gain in more than seven years.

Robert Shiller, Case-Shiller Index co-founder, breaks down the latest numbers on housing, with the “Squawk on the Street” crew.

“Obviously we’re in a housing recovery, at least for the short term,” said Robert Shiller, Case-Shiller Index co-founder & Yale University professor of economics, told “Squawk on the Street” Tuesday. “Housing is a market with momentum and right now, the momentum is up.”

“In the single family realm, I think that there is a chance that there is weakening,” Shiller added. “The housing market has gotten very speculative and it goes through big cycles … It’s a rollercoaster, that’s what these markets have become.”

(Read more: Map: Tracking the recovery)

Shiller said that because of all the speculation in the U.S. housing market, there is an inherent risk of the momentum weakening. The market is driven by “irrational exuberance and that can su

via US home prices rise at marginally slower pace: S&P/Case Shiller.