The construction of townhouses and apartment buildings carried the surge of building permits issued through May in the metro area, according to preliminary figures compiled by the Home Builders Association of Greater Des Moines. Total permits have increased nearly 25 percent to 2,046, but permits for single-family dwellings dropped 18 percent to 784 from 968. Ankeny has been the hotbed of building activity, with 195 permits issued for residences, down from 203 over the same period last year. Permits for townhouse units increased to 299 from 185 in the year-ago period. Permits for multifamily units increased to 963 from 485. The report does not include May figures for Adel and Clive.