The findings coincide with new government figures estimating that £4.6 billion of building work is carried out by cowboy builders operating on the black economy.
'Faced with this irresistible temptation of a cheaper deal, more and more homeowners are taking the bait and falling prey to the cowboys.
'The end result is usually a bodge job, endless delays or even unfinished work, but homeowners have little or no comeback when things go belly-up.'
There are over 100,000 complaints against rogue builders reported every year, while the Office of Fair Trading alone receives up to 200 calls a day.
The NFB poll also revealed more than half of UK homeowners don' t know how to check if a builder is reputable or not.