The concerns over the adequacy of cordons mirror evidence heard this month by the inquiry.
There was no barrier fencing in front of 605-613 Colombo St at the time of the February 2011 quake. The building fell onto a bus, killing eight people.
There was a cordon outside the 603 Colombo St building, which collapsed killing four pedestrians, but engineer Marton Sinclair said the barrier might not have been enough.
"The whole of Colombo St should have, in my opinion, been closed off until the buildings could be made safe or demolished," he said.
Engineer Paul Campbell did an external inspection of 601/601A Colombo St in January 2011 to assess the adequacy of the cordons on behalf of the city council.
Mr Campbell had not been involved in setting up the cordons but was satisfied with their placing. However, he requested an engineer urgently inspect the inside of the building to confirm his decision.
Mr Sinclair also visited the site, on behalf of the owners, but was not concerned about the cordons.
"As far as I could see it seemed consistent with barriers I had seen in other parts of the city - it was outside the veranda line. It looked like quite a common approach. It didn't raise any alarm bells."
However, Mr Sinclair yesterday said he now did not think the cordon had been adequate.
"I don't think the barrier extends far enough to fully protect if the parapet fully peeled off. With the benefit of hindsight, none of the barriers being put up around the city on this sort of site were adequate for upper-level facades."
But Mr Sinclair then said he did not think extending the barrier to outside 601 Colombo St would have made much difference, as the building fell out into the middle of the road.
Royal commission chairman Mark Cooper said the cordoning off of whole streets was an issue which should be "considered pretty carefully" for the future.
"As we are going on in the commission, with the benefit of hindsight, it seems it may have been better to cordon off Colombo St completely."
- APN
