The housing upturn that took root last year is expected to pick up momentum in 2013 but headwinds along a number of fronts could impede the pace of the recovery, according to economists speaking at the International Builders’ Show.

“Nearly every measure of housing market strength – sales, starts, prices, permits, and builder confidence – has been trending upward in recent months and we expect to see gradual but steady growth along these lines in 2013,” said NAHB Chief Economist David Crowe.

In particular, Crowe said that house prices are up nearly 6 percent on an annualized rate over the past 10 months, and that “this has been a trigger for demand to return. People feel comfortable if they buy a house that it will appreciate, not depreciate, in value.”

Other factors that bode well for the housing outlook include low mortgage rates, strong housing affordability, rising household formations and the fact that two-thirds of U.S. housing markets can now be considered improving, according to the NAHB/First

However, Crowe cautioned that builders continue to face several challenges, including stubbornly tight mortgage lending conditions, inaccurate appraisals, rising materials prices and a declining inventory of buildable lots.

Moreover, continuing gridlock in Washington over how much more fiscal tightening is needed to stabilize the debt-to-GDP ratio, along with calls by some policymakers for major changes to the mortgage interest deduction, threaten to negatively impact consumer confidence and future housing demand.

NAHB is forecasting 949,000 total housing starts in 2013, up 21.5 percent from 781,000 units last year.

Single-family starts are anticipated to rise 22 percent from 535,000 last year to 650,000 in 2013, Crowe said. They are expected to jump an additional 30 percent in 2014 to 844,000 units.