The Des Moines Area Association of Realtors said today that 1,090 house sales were completed in July, an increase from 1,038 in June and 830 in July 2012. The average sales price was $172,00, up 11 percent from a year ago. Buyers signed 1,141 contracts to purchase a house, a dip from 1,144 last month, but an increase from 889 a year ago. There were 4,247 active listings, and houses were on the market an average of 83 days.