Commercial office space in Prince George's County has reached an all-time high of 5 million square feet and occupancy rates are averaging 90.8 percent, according to a survey by the county's Department of Program Planning and Economic Development.

About 650,000 square feet of new office space will be completed this year. Most of it is being built along the Beltway, the survey found.

Weaver Bros. Inc. announced the leasing of 14,000 square feet of office space in the Gateway One Building in Crystal City to George G. Sharp Inc., a naval architect and engineering company.

The Grumman Corp. has signed a lease for 18,636 square feet at 1000 Wilson Blvd. in Arlington for a government relations office. Tom Joyce, project manager for Shannon & Luchs, represented both parties in the $2.6 million transacton.

Weaver Bros. Inc. has executed leases for office space in the Beltway View Office Bldg., 6110 Executive Blvd. in Rockville for the following firms: Tavershaw Services Inc., Speedy Printing Center of Executive Boulevard Inc., Pension Administration Inc. and Comprehensive Benefits Service Co.

Four leases have been negotiated in the 1915 I St. NW Building by Shannon & Luchs, which represents the building exclusively. New tenants are: Randall Lewis MD, an orthopedist, who will occupy a 3,200-square-foot office; Engelhard Minerals and Chemicals Corp., which signed a $767,040 lease for 3,264 square feet as headquarters for its precious metals and chemicals trade; Michael E. Dunn & Associates, a political-action consultant, will use 3,278 square feet; and Subway Shops will open a sandwich and fast-food shop in 1,200 square feet under a $360,000 lease.

The real estate division of Blake Construction Co. Inc. announced four lease transactions for the 10-story building under construction at 12th and G streets NW. The law firm of Hyman & Phelps leased the entire top floor and another law firm, LaRoe, Winn & Moerman, will use the entire eighth floor. Six hundred square feet of retail space on the ground floor has been contracted by Kelly Film Express Inc. and the Madison National Bank will occupy 2,172 square feet of ground floor retail space for a new branch. The total aggregate value of these transactions was $7.5 million.

NBI Inc., a word-processing equipment manufacturer, has leased 10,000 square feet in Rosslyn Plaza North, 1777 N. Kent St. in Arlington. The lease was negotiated by Gregg Alexander for the Charles E. Smith Cos. and Ken Born of Savage Fogarty, representing NBI.

The Charles E. Smith Cos. has negotiated a lease for the National Utility Contractors Association for 3,600 square feet in One Crystal Gateway, where the association will establish its national headquarters.