Level 13 Theme Rooms and Costume Hire on Eruera St was covered in knee-deep water on May 24, after a pipe burst on the Hinemoa St side of the building at about 3am.
"It's a big fat mess," owner Debbie Rowles told the Rotorua Daily Post this week.
She and husband Jeff lease a large costume storage room, five other rooms they are converting into party rooms, a meeting room, a toilet, kitchen, and laundry.
"Basically every single thing that was in a box on the floor is ruined."
Rowles lost all of her costume display books and every single vintage handbag she owned.
"If anything had dye, the colour's run and contaminated everything else... We have had to get rid of everything that has got mould. The long dresses [hanging], they sucked up water too."
She said the damaged costumes "stink" and many of her leather items had gone "rusty".
"I have got stuff from Xena and Hercules and the TV shows, so some of that is ruined."
Her furniture was also badly hit.
"We had a lot of chairs that had to go in the tip because they all got wet. Sixteen chairs. We had bought them second hand, bought the material and re-covered them. We gave them a second life. We had tables that we had to throw out too. We were going to upcycle them. So that is devastating."
Rowles had Victoria Grove Costume Hire on White St for 13 years.
Her costume storage was also flooded while she was there, when the roof leaked next door and water went down the walls.
"We lost 86 patterns that time, and we lost another 30 in this one."
She rebranded and moved her business to Eruera St this year.
"It was very ordered and all labelled very nicely. We had only been in that building since January."
Rowles is still finding damaged items and "loss adjusting" with her insurers, but she wants to reopen as soon as possible.
"There are 700 items on the loss sheets now. It just goes on and on.
"Yes we have got insurance, but the costumes are considered second-hand goods so we will not get the total repayments to replace them."
The leased rooms also need extensive repairs.
"All the walls have got to be cut. Everything's got to be re-stencilled. All the fire doors have blown. Twelve doors, gone."
Rowles said she was emailed about the flood "first thing in the morning" and "it was a pretty hard day".
"I can talk now, but early on I would have cried."
Rowles' biggest client is Hobbiton, where she has dressed both staff and visitors for the last 13 years.
"Basically the first thing we pulled out after the flood was all the medieval and Hobbiton stuff."
Debbie Rowles was a television costume designer in the UK, and Jeff was a special effects makeup designer and artist who mainly worked on medical shows.
They moved here almost 14 years ago and Jeff retrained.
He now teaches sculpture, technology and art at Lakes High School.
The couple have been combining their skills to create themed party rooms with a "wow factor" on Eruera St.
"The building here can take up to 100 people including staff. So if there are small conferences in town they could potentially come and have drinks, choose a costume then go on to the rooms for this totally immersive experience," Debbie Rowles said.
The business' recycling component is also important to her.
"I hate that we have become such a throwaway society with these cheap costumes everywhere. It is so wasteful," she said.
Rowles considered closing down the business after last month's damage.
"I was ready to walk away from it all when it was all so stressful. I have aged 10 years in three weeks."
She hopes to reopen in about a month.