The police are appealing for witnesses after a suspected arson attack in Bushey last week.
Firefighters and police were called to the ground floor at The Click Studios, in High Street, on Friday morning after a call from an employee of London Pearl, who are located on the second floor.
Kathy Ran, studio director of Hot Zen Yoga, said she has not been able to open and is currently working with insurance investigators to open as soon as possible.
She said: "We believe the suspects put something burning through the mail slot and then ran off. "There is a considerable amount of smoke damage and looks like the floor, ceiling and wall all need to be replaced, along with the amazing heater for our hot yoga.
"The thermostat actually melted from the amount of heat in the room. All that can be seen is the last of the yoga straps hanging wearily from the wall, all the yoga bricks just disintegrated."
A hose reel was used to extinguish the fire, and no one was hurt. The hall had to be ventilated and the area was cordoned off while investigations took place.
Mrs Ran continued: "We have begun an extremely successful business in Bushey five months ago and have had tremendous support from all of our clients. It's our clients that keep us going and give us hope. We hope to see everyone soon on their mat."
The studio were recently featured in Optima magazine and won the SCOOT small business award in the UK.
Hertfordshire Constabulary believe the incident occurred between 10.15pm on Thursday, January 23 and 8am on Friday, January 24.
A spokesperson said anyone that might have witnessed the incident should contact police, quoting the reference number J2/14/91.