Christchurch roofer Tony Stuart who has been doing essential repairs to roofs and chimneys since the 7.1 magnitude earthquake hit the sleeping city at 4.35am on Saturday, said 80 to 90 percent of older, unreinforced chimneys needed to be inspected, and probably repaired or demolished.
He has been using industrial shrink wrap as a temporary measure to stop chimneys falling until permanent repairs could be done or they could be demolished.
He warned people not to assume because a chimney looked undamaged, it would survive strong winds or another aftershock.
"A lot more are going to come down with the next quake because they have been loosened.
"Without getting close to them you can't tell what the damage is and some of the damage is inside where you can't see it."
He said in most older chimneys the sand and cement mortar had lost its strength and it was only the weight of the bricks which held them in place, not the mortar."
He said people should not risk going onto their roof if they did not know what they were doing and did not have the right gear.
"A lot of people are, but call someone in who has the gear and the experience and who knows what to do."
Mr Stuart said for several years before the earthquake he was advising clients to remove their chimneys because they were not safe.
"They were often in a precarious state but people liked to keep them for the aesthetic value."
He said people were beginning to accept the damage and accept that it had to be dealt with in priorities.
"We are weatherproofing roofs first and securing any chimneys that need to be secured. Often we are taking the chimneys down to roof level and putting iron on because the southerly is coming and it will get very strong and gusty."
He said a lot of the tarpaulins and plastic already on roofs would not survive a strong blow and roofing iron was needed.
Modern brick chimneys with reinforcing should survive, he said.
