Another one fifth admits to trying to out-do their neighbours, says lawn-care company GreenThumb, which carried out the poll.
Neatness topped the list of reasons that caused jealousy with better flowers second and greener grass third. Patios, outdoor furniture and hanging baskets also sparked envy.
David Collison, a manager at GreenThumb, said the trend for tearing up grass and laying decking had been sparked by TV makeover shows such as Ground Force.
But the survey of 2,000 people found homeowners replacing wooden slats with grass was at an all-time high because wood took up too much space and grass looked better.
Three quarters preferred grass to decking, while only a tenth knew neighbours, friends or family who had wooden slats in their gardens.
"It seems many people who have got rid of their decking did so because they missed the pleasure of a lawn," said Collison.
Just over half those quizzed were proud of their patch while the average gardener had spent £1,500 to make their grass and beds look respectable.
His firm’s survey found the average adult spent five hours a week in garden in summer. But four in ten spent as little as an hour enjoying it between April and September.