The area chapter of the Community Association Institute will hold a free seminar for the public on resales of condominium dwellings at 7:30 p.m. Tuesday at the Key Bridge Mariott. Interested persons are invited to attend.

The Ryland Group Inc., which builds houses here and in other parts of the country, has merged with Crest Communities Inc., of Cincinnati. William R. Ryan, president and chief executive of Crest, was elected a director of the Columbia based Ryland firm and senior vice president in charge of the midwestern area.He and James P. Ryan, chairman and founder of Ryland, are brothers.

Construction is under way in Rockville on the North Adams Law Center, a cluster of traditional two-story buildings designed to resemble houses. Thirteen attorneys representing six law firms are the developers. Duane & Duane designed the four buildings, which are being constructed by John L. duFief Inc. The site is at North Adams Street and Wood Lane.

Permanent mortgage financing of $13 million has been arranged for the 10-year-old Iverson Mall shopping center in Hillcrest Heights by DRG Financial Corp. of Washington.

Colonial Homes Inc. has opened a real estate office at 12782 Old Fort Road in Oxon Hill. Don Mangrum, president of the firm, named Dotti Vallone as vice president and sales manager of the new office.