Queensland's biggest builder, Impact Homes, has taken a 4.9 percent stake in its rival, the Simonds Group.
McDonald Jones, the biggest builder in NSW, also holds just over 5 per cent of the ASX-listed stock.
Last month Gary Simonds reached an agreement with Melbourne's wealthy Roche family to take the home builder private with shareholders to vote on the plan in early November.
The Simonds family who own 39 percent of the stock are unable to vote on the scheme.
Simonds posted a $14.9 million annual loss for fiscal 2016.