TGI Friday's is set open a new Brighton restaurant following the redevelopment of dilapidated former post office.
The grade II listed building is likely to cost developers at least £750,000 to return it to working order, after it was left empty for seven years, according to the Argus.
The current planning application lists the building as in "very poor condition" and stated that it currently sits on the council's building ‘at risk' register.
Plans to develop part of the building into a TGI Friday's restaurant were approved last June, but work was held up due to the level of damage to the building as a result of rain damage and squatters.
Mark Thackery, from Walsingham Planning, commented: "At the moment they are just doing all the enabling work to bring the building back into a state where they can put their own mark on it.
"It will cost three quarters of a million just to get the building back into shape before they can begin the conversion. It is damage from the best part of eight years of no use and a lack of investment.
"Some of it is damage from squatters, some from the people who stole lead from the roof, there is quite a bit of water damage. The whole thing is a very slow process. I would think they would want to be in there for Christmas at the latest."
Selma Montford, from conservation group Brighton Society, added: "I will be glad when the building is back in use. It's sad for such a building to be left to rot.
"It's not really suitable for a shop but I think a restaurant is a good idea for the site."