The Environment Court has ordered the owner of an illegal structure anchored to the seabed in Nelson's harbour to take it down.
The shack first appeared on the water as a houseboat in Nelson Haven last July, and the city council has been trying to get it removed since.
The Environment Court has now classified it as a structure because it is fixed to the seabed, has no steering and has not been moved for more than six weeks.
Judge Brian Dwyer ruled its owner, Paul Jepson, has three weeks to take it down.
But council spokesperson Ali Hamblin said the council expected to have to do the work itself.
"It would seem reasonably likely at this stage," she said.
"The owner has not co-operated in any way with any council requests up to this point, so we're not expecting that that is likely to change."
Ms Hamblin expected the council would serve the papers on the owner next week.