Sonoma County apartment rents leveled off late last year, part of a national hiatus that a real estate information company attributed to increased demand for single-family homes.

The county’s average rent rose $3 in the fourth quarter to $1,278 per month, compared to $1,275 in the third quarter, according to RealFacts of Novato.

The county’s occupancy rate declined by a half percent in the fourth quarter to 96.6 percent.

“Rents have hit the wall — at least for the time being,” said RealFacts founder and managing member Sarah Bridge. “Whether this is due solely to an increased demand in for-sale housing remains to be seen.

“But the fact is, when people leave their rental unit to buy a house, a unit becomes vacant. Landlords can only raise rents so long as there is continued demand to fill the unit.”

County rents increased an average of 4.8 percent last year and 3 percent in 2011. In the previous four years, rents rose a total of just 5 percent as landlords showed reluctance to seek increases during the worst of the economic downturn.

Nationally, the average rent declined by $2 to $1,040 a month in the fourth quarter. During the previous six months, the average rent had risen $34, or 3.4 percent.

RealFacts previously predicted rents would peak in early 2013 in San Jose and San Francisco metro areas, which have been leading the nation for increases, Bridge wrote in a press release. However, “it appears this has already happened in the fourth quarter of 2012.”

Average rents declined 1.4 percent last quarter in San Jose to $1,954 a month and stayed unchanged for San Francisco at $1,859.

— Robert Digitale