Dundee councillors have agreed to spend more than £4 million to fix roofs their own workers installed that did not meet British safety regulations.
More than 400 homes are affected by the blunder, which went undetected for four years.
The issue relates to a revision of the national standards dictating how roof tiles should be installed.
In 2015, the British Standard was revised requiring tiles to be attached to buildings with a greater number of fixings to counter increased high winds in the UK.
However, the updated rules were not adopted by Dundee City Council housing bosses until 2019 - by which time hundreds of new roofs had been installed that were not up to scratch.
On top of that, six non-standard roofs have already been affected by high winds, costing the council more in repairs.
Elaine Zwirlein, the authority's neighbourhood services boss, said the overall cost of replacing the roofs would be around £4.4 million, over a two and a half year period.
In a report to councillors delivered last night, she wrote: "The implications of the changes to standards were not [picked up] until the issue was identified late 2019.
"This has resulted in 450 roofs not being installed to the full requirements of British Standards, covering 262 owners and 894 tenants."
Council leader John Alexander has promised a full investigation into the error.
The local SNP group leader said: “There will be an internal investigation through our independent audit process, a further report to the scrutiny committee chaired by the opposition and another to the policy and resources committee.
“In addition, the administration will be seeking agreement from opposition politicians for an external independent viewpoint.”
Mr Alexander added: “There were multiple points of failure including, as noted in the report, within the clerk of works service, whose sole function is to ensure standards and quality specifications are met.
“As soon as there was full clarity on the extent, nature and potential costs of this a report was brought forward to committee and councillors were briefed.”
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