BELFAST, Maine — Front Street Shipyard, the high-end yacht service business that set up shop along the city’s waterfront a year ago, is expanding with the purchase of the adjacent Belfast Boatyard.

Front Street Shipyard’s partners have given their approval to the terms of a purchase and sales agreement, company president J.B. Turner said Monday, as has Alex Turner, owner and operator of the Belfast Boatyard. The parties are expected to sign the agreement next week.

The Belfast Boatyard leases its site from John Holmes, owner and operator of Consumers Fuel and a small marina near his property on the south side of Main Street. J.B. Turner said negotiations are under way with Holmes for Front Street to secure a long-term lease for the land.

J.B. Turner said the deal with Alex Turner — the men are not related — is mutually beneficial, since Front Street Shipyard will gain much-needed off-site boat storage and deeper water near the shore, while Alex Turner, who has operated the business for the last three decades, is nearing retirement age. Alex Turner approached Front Street about a purchase earlier this year, J.B. Turner said.

A telephone message left for Alex Turner was not immediately returned.

The purchase is expected to close in September, J.B. Turner said. The price of the purchase was not disclosed.

“We realized last spring, when we were full, that we needed more off-site storage,” J.B. Turner said Monday. The Belfast Boatyard has been storing boats on a 6.5 acre site off Route 137 for about 20 years, as waterfront land has become more valuable.

With the purchase of the Belfast Boatyard, Front Street also gets a bulkhead with deeper water.

Front Street handles sailboats 82-feet and longer; when work calls for hauling out such yachts, the first step is to remove the mast. The longer the boat, the longer the crane used to lift the mast off the vessel must reach, Turner explained. With 14-feet of water at low tide, the larger sailboats would be able to tie up closer to land, so a smaller crane can be used.

In all, the purchase of Belfast Boatyard brings Front Street an additional 500 feet of deepwater-frontage, 22 boat slips, 20 moorings and harbor floats.

The boatyard property buildings will be updated to be consistent with Front Street structures, and eventually, the company’s business office will be located at the Belfast Boatyard property. Crew quarters for yachts that come to the yard for work also may be added there.

Front Street now has 72,555 square feet of yacht storage space and 10,320 square feet of shop space on its 6-acre site.

J.B. Turner said the two businesses had different clientele, and were not strictly competitors.

In a press release issued about the pending purchase, J.B. Turner is quoted saying the move is part of the company’s strategic growth plan. “Our initial goal was to create a yard equipped to service most any yacht that visits New England. We’ve reached that goal.”

Front Street’s principal owners include J.B. Turner, Taylor Allen of Rockport Marine, Steve White of Brooklin Boat Yard and Ken Priest of the Augusta-based Kenway Corp. Front Street employs 82, and hopes to add jobs as it grows, according to the press release.