An organisation targeting leaky home syndrome says some real estate agents and vendors failed to tell prospective buyers about leaks.
The Home Owners and Buyers Association says it is taking a stand to protect unsuspecting buyers.
Association president John Gray says people need to be aware of the risks involved, particularly when buying cheap houses and apartments which can be mistaken for bargains.
He says vendors or their agents cannot be trusted to tell the full story.
Mr Gray says although vendors are obliged to inform the buyer of any problems when specifically asked, there are many cases where that information is withheld.
He says the old adage of buyer beware remains in force, and buyers should list their questions in writing and ensure all responses are made in writing also.
However, the Real Estate Institute is questioning the Association's claims.
Chief executive of Harcourts, Brian Thompson, says it's scandalous to suggest agents withhold information.
"There might be the odd bad egg in any basket who could make a poor decision but it beggars belief that anyone would suggest that that's a general operational move," he said.
Mr Thompson says agents are professionals - and are well aware they're liable for prosecution if they fail to disclose information that could affect a buyer's decision.