The condition of the UK's highest railway was "disappointing for its age", according to a newly-released engineers report.
The Cairngorm funicular opened in 2001, but has been closed since September last year due to structural problems.
Highlands and Islands Enterprise (HIE), which owns the railway and wider Cairngorm Mountain snowsports centre, has released the report from last year.
Engineers concluded the general condition of the structure was "poor".
They said there were "widespread minor deficiencies".
In the July 2018 report, the engineers also said: "The structure's condition is disappointing for its age, regardless of its environment.
"There are various defects appearing that demonstrate an ongoing deterioration of the structure."
A second report, also released by HIE, confirmed work was required to strengthen the railway's piers, beams and foundations.
It said new sliding bearings better able to handle a heavier load and "movement capacity" should be installed.
HIE has released the documents under Freedom of Information rules.
The railway connects a base station with a restaurant, and wider ski centre, 1,097m (3,599ft) up Cairn Gorm mountain near Aviemore.
HIE has said its intention would be to repair the railway at an estimated cost of £10m.
The Scottish government will be asked to make a decision on the repairs.
HIE, a public body, said it expected to have the business case for this work to be ready to submit to the government next month.
Meanwhile, it has also announced it was making preparations for public consultation on a new masterplan for the Cairngorm Mountain resort.