George Smallwood’s Bee Eco Shed won the top spot in the annual competition.
The handmade structure is a self-watering and self-sufficient home for vegetables, herbs and insects.
Mr Smallwood, from Sheffield, said winning the 2018 title and a £1,000 cash prize was a “welcome surprise”.
“We hope our shed will inspire others around the UK to create spaces for wildlife in their gardens,” he added.
“We’re so proud that our shed has become a habitat for nature in a small urban garden, showing you can always do your bit for making a home for nature.”
There were eight categories, including eco-friendly creations, budget outbuildings and historic-like structures.
Among the innovative buildings were a Legoland-inspired haven, a black cab converted into an outdoor bedroom, and a structure made out of glass bottles.
Competition founder Andrew Wilcox said: “The competition was extremely tough this year, from a musical shed on the water, to a taxi, to an authentic Irish pub.
“George’s shed stood due to its impressive, handmade structure but also because of its unique story and special purpose.”
The Cuprinol-sponsored contest, now in its 11th year, attracted nearly 3,000 entries and 16,000 public votes.