Council officers in Blackpool were shocked to find tenants living in a property with sections of its floor and ceilings missing.
Three occupants had been paying £500 a month to live in the house on Tyrone Avenue, North Shore, for 12 months while the landlord renovated it.
Officials ordered its closure after a routine inspection found the rear of the property in a state of disrepair.
The council said it was a "dangerous and uninhabitable environment".
The inspection was carried out on 10 August and revealed that tenants had been living in the property while the landlord renovated the rear.
The missing floor had left hazardous gaps between the first and ground floor, the authority said.
Officers also found exposed brickwork, dust and debris, exposed live electrical cables and no fire separation.
Blackpool Council served an Emergency Prohibition Order on the property, effectively preventing it being rented to the tenants.
The council said they had been exposed to "serious and imminent risk" by living there and had now been given help to find alternative accommodation.
Tim Coglan, the council's head of quality standards, said: "The council will always take immediate enforcement action against dangerous properties.
"Strong partnerships between the council and other services will ensure that no stone remains unturned during our clean up campaign and officers are actively seeking out such poorly maintained and managed tenancies."