Mallorn ladders are not directly mentioned in Tolkien's works; instead, the Galadhrim seem to use rope ladders to access their flets. Flets were small platforms on the trees of Lothlórien, from which the Elf wardens stood guard. (True flets have yet to be added).
Note that only regular Elven Treehouses uses ladders; Grand Elven Treehouses have stairs leading up to the structure.
|The Elves of Lothlórien|
Elf (Banner Bearer, Warden, Warrior)