Council staff say the backlog resulted from the large number of consent applications received in the last week of February.
Chief building control officer Neil McLeod said the council's building consent authority received about 125 consent applications in the week before March 1, when a new law took effect requiring most residential construction work needing building consents to be undertaken by licensed building practitioners.
The influx equated to about five weeks' work in one week, Mr McLeod said, and included several applications for multiple dwelling projects.
It caused delays in processing subsequent consent applications. The problem was made worse by the retirement of one staff member and the unexpected resignation of another.
"We kept thinking we were just going to be be able to deal with it, and then that happened."
At the worst, "one or two" applications took 30 days to complete, 10 days over the 20-day statutory requirement.
Mr McLeod said he decided in late May to send a batch of applications to the Auckland company to "break the back" of the workload.
With Dunedin staff working overtime, the authority managed to bring processing of applications back under 20 days earlier this week, and ceased using the Auckland company.
Outside companies had been contracted to help with backlogs before, although he could not remember the last time that happened, Mr McLeod said.
The authority was resourced to deal with the average number of consents received each year, but there were always peaks and troughs and, with a reasonable staff turnover, it was not unusual to go over the 20-day limit, although the situation was usually corrected without any outside assistance.
Consents were dealt with on a first-in, first-served basis, so if required information was missing, it could be some days before that was noticed - and it was not an unusual occurrence.
The process went on hold if the council had to ask for any more information, and it did not start again until that information was received.
The authority had calculated between 40% and 60% of consent applications in Dunedin had some of the required information missing.
If people got all their documentation together before they lodged their applications, the process should go quickly and smoothly, he said.
"While I accept we were pushing the limits and we were not coping, this thing cuts both ways."
Otago Master Builders Association president Mark Ward said builders still thought the consent process took too long and was inconsistent and, in the absence of the outcome of a review of the department, he had recently met Cr Kate Wilson to express the industry's concerns.
Cr Wilson referred the ODT to council general manager operations Tony Avery, who said the building control department had been reviewed and the outcome of that should be known within a month or two.
He said there had been a "fundamental re-look" at every part of the department, including processing systems and staffing.
The work had been peer-reviewed by Queenstown and Central Otago council staff and an external reviewer.
No decisions had been made on what would change, he said.
