The National Association of Home Builders (NAHB) released its housing market index for the U.S. on Monday. The NAHB housing market index remained unchanged at 58 in May, missing expectations for an increase to 59.

A level above 50.0 is considered positive, below indicates a negative outlook.

The buyer traffic sub-index remained unchanged at 44 in May, the current sales conditions sub-index remained unchanged at 63, while the sub-index measuring sales expectations in the next six months increased to 65 from 62.

"Builder confidence has held steady at 58 for four straight months, which indicates that the single-family housing sector remains in positive territory," the NAHB Chairman Ed Brady.

"The fact that future sales expectations rose slightly this month shows that builders are confident that the market will continue to strengthen. Job creation, low mortgage interest rates and pent-up demand will also spur growth in the single-family housing sector moving forward," the NAHB Chief Economist Robert Dietz said.