Shares in Calgary-based DIRTT Environmental Solutions Ltd. fell by 18 per cent on Tuesday after it made the surprise announcement its board had replaced founder Mogens Smed as CEO.

The office interior design and manufacturing company closed at $5.53, down $1.21 on the day.

A company press release presented the changes as part of succession planning, with Smed staying on as executive chairman but, on a conference call, Smed said he had only learned of the changes last Friday and "haven't really got a clue" what his new role will be.

Lead director Steve Parry, previously chairman, said on the call that the appointment of Michael Goldstein as interim CEO was a "proactive" move made after the board noticed "cracks" in company processes, without being specific.

He says the decision to replace Smed was made based on an internal board assessment of DIRTT's capabilities, earning power, growth opportunities, governance and shareholder returns.

DIRTT also announced the appointment of Peter Henry as interim chief financial officer, replacing president and interim CFO Scott Jenkins.