The second phase of the Grenfell Tower inquiry will not start until autumn 2019 at the earliest.
A barrister for one of the residents, Rajiv Menon QC, told the inquiry the hearings may even slip to 2020.
Inquiry chairman Sir Martin Moore-Bick will confirm the new timetable on Wednesday as the first phase concludes.
The length of time will allow lawyers to digest a vast amount of evidence, some of which will be passed to a coroner.
A number of inquests into the deaths at the tower are expected to conclude next year.
The hearings have so far been concentrating solely on the events of the night of 14 June 2017 in which 72 people died.
The next phase will examine the wider causes, including the use of cladding blamed for helping the fire spread.
The first phase heard detailed evidence that the plastic material added to the building and the redesign of its windows both allowed the flames to spread rapidly.
Phase two will examine why those changes were made as part of the Grenfell refurbishment.
Victims' barristers also want the inquiry chairman to make early findings to improve the safety of other residential tower blocks.
Meanwhile, Anne Studd QC, representing the Mayor of London, has reiterated concerns about the inquiry continuing to be held in central London.
On Tuesday she said phase two should be held closer to the tower in North Kensington, west London, for the "convenience of core participants with competing daily commitments in their locality".
A criminal investigation into the fire is continuing.