It also said there was no geotechnical report in the HDC files provided for the investigation, but data indicated ground beneath the building consists of "unconsolidated to poorly consolidated mud, sand, gravel and peat".
HDC chief executive David Clapperton responded, stating that he welcomed the release, and felt the community was frustrated about the ongoing issue.
He acknowledged the mayor's report differed from previous reports, but reiterated that the building was sound.
"It is important to remember the report, like three previous reports carried out by Opus, IPS Consulting and Koru VSL confirm the building is currently safe, that the building is not earthquake prone," he said.
Mr Feyen disagreed, saying the new report cast major doubt on previous information.
"Just about everything that I've ever heard mentioned in council [about the safety of the building] is severely challenged by this report," he said.
One major difference refers to IL4 rating, a seismic measure referring to the Importance Level of the building.
"Structural Concepts' opinion is that the building has a low IL4 rating which means the building may be unavailable for use by Civil Defence in the event of a large earthquake," Mr Clapperton said.
"Given this, I informed HDC's emergency operations controller and Horizons Regional Council of the report."
Mr Feyen felt there were distinct differences in the quality of the reports, alleging the prior council ones were "desktop" reports.
In his opinion, even as a "layman", it was obvious that there were serious concerns with the building.
Mr Clapperton said that since receiving the report, he has requested Opus engineers, who carried out a prior report, work through the differences between reports with Structural Concepts.
He said both engineering firms have indicated a willingness to work through the results to come up with an overall rating for the building and this may mean that the final rating may differ from either report.
"That would cost ratepayers about $50,000, and costs would escalate if the professional opinions differ, as this will lead to a peer review being required."
However Mr Feyen said he believed that process may reveal even more issues.
"When reports are reviewed they're usually worse," he said.
Mr Feyen is also seeking reimbursement from council for the cost of the Structural Concepts report, which cost him more than $24,000.
REPORT
Recommendations in the Structural Concepts Report:
1. Relocate the Civil Defence Headquarters to a new location/independent building.
2. Confirm geotechnical conditions before undertaking any strengthening design.
3. Provide additional bracing elements to roof spaces or upgrade same to improve transfer capabilities of roof bracing.
4. Provide diagonal brace elements to the posts supporting the roof over the Council Chamber to improve transfer of lateral loads to other elements.
