An independent report was expected to be finished by the New Year.
However, it is understood a delay means city councillors will not now consider its findings until February.
A crisis that began with a collapsed wall at Oxgangs Primary led to disruption for about 7,600 pupils.
Once the repairs were complete, City of Edinburgh Council asked John Cole, an experienced architect from Northern Ireland, to investigate.
He was due to report before Christmas. But it is understood, although not a legal requirement, he has been advised that any organisation or individual criticised in the report must be given time to respond.
It means it will be February at the earliest before the report is then published and councillors are able to consider Mr Cole's final conclusions.
A City of Edinburgh Council spokesman said: "As planned, the chairman of the inquiry intends to provide his report to the council's chief executive by the end of the year.
"We expect the final report to be considered by councillors early in the new year."
The schools which were closed in April 2016 were all built or refurbished as part of the same public private partnership (PPP) scheme.
The problems - with wall and header ties used to hold exterior and interior walls together and attach them to the rest of the building - first became apparent when part of a wall at Oxgangs fell during stormy weather.
Safety inspections were ordered and pupils were bussed to other schools across the city while repairs were carried out.
The investigation into building failures that forced the closure of 17 Edinburgh schools earlier this year has been delayed by at least a month, BBC Scotland has learned.