A wall near the women's entrance to the amenities block at the town hall parking lot was damaged on Friday morning.

Horsham police believe a vehicle backed into the building.

Horsham Rural City Council staff received an early wake-up call after security and cleaners noticed the brick wall had been damaged about 4.30am.

The area was fenced off and council technical services director John Martin said the affected walls would be braced this week.

Men will still be able to use the toilets because their entrance was undamaged.

The toilet block is set to be demolished as part of the city's town hall redevelopment, which begins next week.

"Given where we are with planned commencement of work, I expect the toilets will remain closed," Mr Martin said.

Kane Constructions will set up its site office, lunch sheds and amenities on January 14. 

The construction site will be fenced off from January 20.

The contractor had planned to use the toilet block for construction workers.

Mr Martin said he expected the toilet block would be demolished in February, according to Kane Constructions' plans.

"There will not be any temporary public toilets in place in Pynsent Street during construction. People will have to seek other alternatives," he said.

The redevelopment will occupy the entire carpark space.

"The whole western part of the carpark directly behind the town hall building will be demolished, as will the supper room on the north-eastern corner of the existing building, the existing toilet area within the town hall and a small building attached at the rear of the town hall building which houses the heating furnace," Mr Martin said.

The town hall auditorium will remain.

Alternative toilets are in Roberts Avenue at the corner of Firebrace Street, in May Park and in the supermarket carpark on the corner of Darlot and Wilson streets.

Acting Sergeant Chris van Burren asked anybody with information about the toilet block damage to call Horsham Police Station on 5382 9200.