Homebuilder sentiment is at an all-time high, as city-dwellers seek out suburban homes during the coronavirus pandemic. But experts warn that an overcorrection in the lumber market could spell trouble for homebuilders and homebuyers alike.

U.S. lumber prices rose 170% from April to an all-time high in August and moderated only slightly in September, driving the cost of the average new home up $16,148 since April 17, according to the National Association of Home Builders, a Washington, D.C.-based trade organization.

“The dark cloud on the horizon of the single-family side is lumber prices,” National Association of Home Builders CEO Jerry Howard told Yahoo Finance The Ticker. “If we continue to see this type of increase in the prices, or — I’ll make an even more dire prediction — if prices don’t come down, you will see a slowdown in housing.”