Housing construction in the Twin Cities was down slightly this month because of a modest decline in apartment construction, which concealed a slight increase in construction of single-family houses.

During October, 487 permits were issued to build 1,029 units in the 13-county metro area, according to data compiled by the Keystone Report for the Builders Association of the Twin Cities (BATC). That was a 19-percent increase in permits, but a 22-percent decline in the number of planned units.

Single-family homes accounted for 538 of the planned units for the month, an almost 40 percent increase over last year.

So far this year, builders were issued 4,502 permits to build 8,618 units, besting last year's unit count by 25 percent.

Minneapolis, Plymouth and Ramsey were far and away the busiest cities for housing construction during the month, accounting for half of all planned units.

Apartment construction has been robust, and has led the recovery for the construction industry. But it tends to be a volatile sector of the industry because a permit for single building can add hundreds of units to that month's total. This is also a time of year when construction activity tends to slow.