“A lot of the sub-contractors are seeing an increase in business, yet they’re reluctant to hire staff or have an inability to hire skilled labor, so we’re seeing delays with framers coming onto our properties to frame the houses, we’re seeing challenges with drywall finishers and painters,” says Paul.

Many builders are also seeing supply constraints, as they did not expect to see such a surge in demand. Demand is strong in large part because there is such a small supply of existing homes for sale nationwide, and because banks have been exceedingly slow to work through foreclosures in some states.

(Read More: Home Prices See Record Gain in April)

“About one third of homes sold are completed, down pretty significantly from where we were earlier in the cycle, which was in the 50 to 60 percent range,” notes David Goldberg, an analyst at UBS.

While the major public builders have not voiced concern publicly over risks to their backlogs, the analysts that cover them say if rates continue to rise, they will not be able to ignore it.

—By CNBC’s Diana Olick. Follow her on Twitter @Diana_Olick or on Facebook atfacebook.com/DianaOlickCNBC.

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Article source: http://www.cnbc.com/id/100849156