* Cuts profit view for second time in four months
* CEO Mark Adamson step downs
* Shares fall more than 8 percent to one-year low
* New Zealand stock exchange looking into downgrade (Adds analyst comment, bourse probe, context)
By Ana Nicolaci da Costa
WELLINGTON, July 20 (Reuters) - New Zealand's Fletcher Building Ltd, the biggest construction firm in a country where migration is fuelling a building boom, lowered its profit estimate for the second time in four months on Thursday, prompting a stock exchange enquiry.
Fletcher's share price sank to a one-year low after the firm said losses at its building and interiors unit were steeper than previously estimated, and that its chief executive of five years had left the firm.
New Zealand's construction costs have risen by half in under three years as rebuilding following a 2011 earthquake stretches resources, leading to project delays. In May, outgoing CEO Mark Adamson told Reuters the labour market was so tight that manual workers were seeking high wages to "hold a hammer."
"I am disappointed to finish my tenure on the back of a challenging result in the Construction Division, however I am proud of what has been achieved over the last five years," Adamson said in a statement.
Adamson's departure and a second earnings downgrade prompted New Zealand Stock Exchange operator NZX Ltd on Thursday to say it would look into into the latest revision.
The exchange is already investigating the previous downgrade in March which came a month after Fletcher confirmed guidance in a half-yearly report, and which sent its shares down 12 percent.
Fletcher now estimates operating profit of NZ$525 million for the year ended June 30, below its March range of NZ$610 million to $650 million, which in turn compared with an initial NZ$720 million to $760 million confirmed in February.
Its shares fell as much as 8 percent to NZ$7.38, the lowest since March 2016.
Fletcher Chairman Sir Ralph Norris said it was "very disappointing" to see further losses in the building and interiors unit business and that "the Board believes it is the right time for Mark to leave."
Francisco Irazusta will take over as interim CEO, effective July 24, Fletcher said. Irazusta joined the firm in March 2015 and is currently chief executive of its international division.
Andy Bowley, head of research at investment firm Forsyth Barr, said the downgrade was unsurprising given industry capacity constraints and escalating costs.
"The change in leadership adds a level of uncertainty as to future strategy and operational focus," he said. "While we see further risks in the construction book given the environment, the impact on future earnings of any further losses shouldn't be substantial." (Reporting by Ana Nicolaci da Costa; Additional reporting by Tom Westbrook; Editing by Christopher Cushing)