* Shares drop after Q1 net loss widens unexpectedly
* Cost overruns trigger renewed concern from analysts
SAO PAULO, May 9 (Reuters) - Brazil's Brookfield Incorporações SA was the biggest loser on Brazil's benchmark Bovespa stock index on Thursday after the homebuilder posted an unexpected first-quarter net loss and lowered its profit-margin estimates for the year.
Brookfield booked a loss of 47.7 million reais ($23.9 million) on Wednesday as it continued to struggle with the cost overruns that have plagued its performance in recent years.
The homebuilder also revised its gross margin estimate for 2013 to 20-24 percent, compared with a forecast of 28-30 percent made at the end of 2012.
Brookfield shares fell 3.33 percent to 2.03 reais in afternoon trading, while the benchmark Bovespa index was up 0.27 percent.
"In our view, additional execution issues might have arisen indicating that profitability could remain depressed for longer," Credit Suisse analysts led by Guilherme Rocha said in an investor note on Thursday.
The company, along with many of its competitors, is struggling to rein in costs and reduce debt. Overly aggressive expansion in recent years led to cost overruns, project delays, and a 388 million reais net loss in 2012.
Brookfield expects a "substantially greater volume" of deliveries to occur in the second half of 2013, executives said during a conference call held to discuss earnings on Thursday. Management also expects cash flow to turn positive in 2014 and said they are negotiating with banks to roll over debt expiring this year.
"We acknowledge that Brookfield is still far from completing its turnaround strategy, but we believe the negatives are already priced in," Espirito Santo Investment Bank analysts led by Eduardo Silveira wrote on Thursday. They cited the better creditworthiness of Brookfield's customers compared with those of its competitors and its lower execution risk.
$1=2.00 Brazilian reais Reporting by Juliana Schincariol and Asher Levine; Writing by Asher Levine; Editing by Peter Galloway