Carrollsburg Square, the 425-unit complex of high-rise apartment buildings and town houses in Southwest, is poised to be sold in January for about $9 million to Rozansky & Kay, the firm that now is developing the Rockefeller estate. The current ownership of Carrollsburg Square is a group headed by George and Donald DeFranceaux and a limited partner. The 15-year-old luxury rental property in the block bounded by 3d. 4th. M and N streets, is near a proposed Metro stop. The property, which was developed under an architectural competition by the Redevelopment Land Association, is adjacent to Tiber Island, a similar complex owned by another group. Long rumored as another candidate for intown condominium conversion. Carrollsburg Square may be headed in that direction early next year. About half of the 38 town houses were originally marketed for condominium ownership, when that form of real estate holding was in a pioneer stage here.

The 166-unit Garfield apartment at 5410 Connecticut Ave. NW has been converted to condominium ownership by the Conrad Cafritz group. Cafritz, who recently converted and sold out 2029 Connecticut and the Parker House at 4700 Connecticut, said that 105 of the Garfield units already are under contract, many to residents in the 19-year-old building, which was purchased from Julius Sankin. He plans to keep his own realty office there. The Garfield, which will be ready for owner occupancy in 1979, will have a lobby decorated as a library.

Office leasing specialists, of whom there now are more than 60 in this area, compared with two dozen a decade ago, regard the current market as "crazy." Lack of available new space spurs the market but inhibits some tenancy. Big users of downtown space, who now are committing on leases up to $14 a square foot, are preleasing spaces larger than needed as a hedge against inflation for future expansion. Then those tenants become subleasers of smaller spaces, which are still available. More than 10,000 square feet constitutes a big user. Fernando Barrueta, a vice president of the Braedon Companies, said that leasing rates have increased $1.50 to $2 a square foot within the past year. Only a sharp downturn in the general economy is likely to cool off the hot downtown and suburban office leasing market in thenext two years. Neil J. Simon of the Carey Winston Co. pointed out that office leasing near Metro stations is a "hot ticket" today.

Architect Roger K. Lewis, whose firm designed the tastefully contemporary Dana Place Co-operative on a small northwest site six years ago, did the drawings for ParkSlade, a 20-unit group of "English flats" in two-story brick buildings in the Pikesville area of Baltimore. Lewis said that the roof surfaces of attached garages will be the fenced terraces for upper-level residences. Lewis is both architect and developer of the 1,250-square foot units expected to sell for $69,000. Harkins Commercial Inc. of Silver Spring is the general contractor. Occupancy is scheduled eary next year.