The Gaiety Theatre is to under- go €100,000 of repair work following a fire.
While there was no damage to the building's structure, the stage floor and orchestra pit have to be replaced, which will take a week after the current production of John B Keane's The Field ends.
Theatre manager Alan McQuillan said the fire was started deliberately three weeks ago.
"At around 6am one of the homeless people set a bin on fire in Tangier Lane behind the Gaiety," he said.
"It was a big plastic wheelie bin that melted and set fire to the shutter where all the sets are loaded in.
"The heat began to penetrate through the shutter but the fire didn't carry into the theatre. What happened was that all the smoke got in and the fire sprinkler system activated.
"We got a call from the monitoring station to say there was an emergency at the theatre and the fire brigade got the call then and there were five units that arrived to deal with it.
"No performances were affected, but there was a lot of water damage to the main stage due to the sprinkler system and also to the sub-stage leading into the orchestra pit.
"At the moment we have two men on 24-hour security monitoring the building in the event that anything happens. We estimate the whole stage floor will have to be replaced eventually, along with the orchestra pit."
The theatre's laundry equipment was destroyed and at least nine skips of fire-damaged material have been removed.
Mr McQuillan said recent issues are making life particularly hard for everyone at the Gaiety.
"I'm working there over 30 years, and it's in the last three years that it's got bad with the homeless coming into the lane, shooting up and using it as a toilet and leaving needles," he said.
"We've applied to Dublin City Council to get a gate erected in the laneway to stop the anti- social behaviour.
"If we had the gate, it could be monitored through our security system because we have CCTV in the lane and that's monitored 24 hours a day."