Sales of new homes are near 47-year lows, yet the supply of new and existing homes is expected to grow in the months ahead as construction ramps up and a wave of foreclosed homes hits the market.

In June, new-home sales were running at a seasonally adjusted annual rate of 330,000 units, the Commerce Department said Monday. While that was up 23.6% from the all-time low of 267,000 in May, the June figures were the second lowest on record.

"What...