Stephen Ratcliffe, chief executive of the Construction Confederation, said the public still had to be convinced about the perils of cowboy builders.
New government figures estimate that £4.6bn of building work is carried out on the black market.
Chief executive of the NFB Tony Maynard said: "Rogue builders tempt customers by offering to waive VAT charges on building work in return for cash-in-hand payment." The survey also revealed that more than half of UK homeowners do not know how to check if a builder is reputable.
A cross-section of 500 homeowners was surveyed.
Maynard said homeowners needed to do their homework before employing builders.
He said: "Your house is the most expensive purchase you are ever likely to make. Still, most people get caught out by the cowboys because they don't ask the right questions.
"Armed with the right information, hard-pressed homeowners are much more likely to get the hassle-free, professional results they deserve." More than 100,000 complaints over disreputable builders are made each year; the Office of Fair Trading receives up to 200 calls a day.