WASHINGTON — Sales of previously owned homes slumped in November to the lowest level since last April as a change in industry rules lengthened the amount of time it took buyers to close on a deal.

Closings on existing homes, which usually take place a month or two after a contract is signed, declined 10.5 percent to a 4.76 million annual rate after a revised 5.32 million pace in October, the National Association of Realtors said Tuesday. November sales were weaker than the most pessimistic forecast in a Bloomberg survey.

“November home sales without a doubt were heavily impacted by a new federal government rule regarding closing documents,’’ Lawrence Yun, NAR chief economist, said in a news conference as the figures were released, adding that sales may rebound this month. “Buying interest is there, it’s just that closings are not happening on a timely basis.’’

Housing has helped prop up growth this year, thanks to cheap borrowing costs and a labor market that’s given Americans greater job security. Faster wage growth would help provide the next leg of support for residential real estate, especially by assisting first-time buyers who have found it difficult to save enough for a down payment.

The length of time it took buyers to close on a home purchase was 41 days in November, up from 36 days a year earlier. Yun attributes this to a change in regulation that consolidated the closing process and the introduction of new forms that are processed by lenders and title companies.

Higher prices are leaving home purchases further out of reach for some first-time buyers.

US home prices in October surpassed their 2007 peak, a Federal Housing Finance Agency index showed Tuesday.