The agency worker was employed by a piling subcontractor on the job in Maidenhead.
McAleer & Rushe said the tragedy was a “freak accident”.
A company statement said: “Following a thorough site investigation by the Police and HSE, initial reports indicate that the root cause of the incident would appear to be a catastrophic parts failure on the tracks of the piling rig .
“This occurred during a routine maintenance procedure, completely outside of any construction operations.
“Having finished their site investigation the HSE confirmed that they were fully satisfied with our health and safety system and its implementation on site.
“Our entire team has obviously been devastated by the events of Tuesday 13th May and our thoughts and sympathies go out to the family and friends of the deceased.
“We would like to record our thanks to the Emergency Services for their swift response to this tragic incident.”