WASHINGTON – New residential construction surged 15 percent in September, turning in its best performance in 17 months, though economists warned that a housing recovery has yet to take hold.

While new construction is key to getting the economy going, much of the new building came from the apartment sector, which can be very volatile. Many economists also noted that permits pulled for new construction, also an important measure of builders’ plans for the future, declined in September.

Builders started new residential units at a seasonally adjusted annual rate of 658,000 in September, a 15 percent increase from the prior month and up 10.2 percent from the same month the year before, according to the U.S. Commerce Department.

Single-family homes were built at a rate of 425,000 units, which is only 1.7 percent above a revised August estimate, meaning the bulk of the increase came from the building of structures with five or more units.