Burt Hill, a Butler architectural firm, will merge with Stantec of Edmonton, Canada.

The two companies signed a letter of intent on Sept. 3, and now they will follow a 90-day "due diligence period" before the merger becomes official, J. Rossi, Burt Hill's communications director, said today.

Burt Hill is an international architectural and engineering firm that was founded in Butler in 1936 by G. Edwin Howard.

Ralph Burt, Alva Hill, Dick Rittelmann and John Kosar followed 30 years after the founding, later naming the firm Burt Hill Rittelmann Kosar.

In recent years, the name was trimmed to just Burt Hill.

It has more than 600 employees in 13 offices, including three offices overseas.

Stantec, a design firm, has announced plans to acquire nine firms this year and will soon have more than 10,000 employees in more than 150 locations in North America. Stantec trades on the TSX and the NYSE under the symbol STN.

Peter Moriarty, Burt Hill president and chief executive officer, will continue with Stantec in a leadership role.