Sales of new U.S. single-family homes tumbled to a 14-month low in June and sales in the prior month were weaker than initially estimated, the latest signs that expensive lumber and shortages of other building materials were hurting the housing market.

The third straight monthly decline in sales reported by the Commerce Department on Monday followed news last week that permits for future homebuilding dropped to a nine-month low in June while home resales rebounded modestly. Higher production costs are forcing builders to scale back, keeping supply tight and boosting home prices to the detriment of first-time buyers.

“Home builders continue to hold back on contracts for new homes given input cost and availability uncertainties, with significant uncertainty about what it will cost to build a house and when it can be delivered,” said David Berson, chief economist at Nationwide in Columbus, Ohio. “Until builder costs and supply-chain problems become less of an impediment, it is hard to see new sales picking up significantly in the near term.”