The firm, which was set up five years ago, started out as a mechanical contractor and branched out into electrical services more recently, counting the Savoy Hotel refurbishment among its recent projects.
It operated from a fabrication workshop in Rainham and offices in London.
Hapap worked for Skanska, Chorus, Overbury and Briggs and Forrester on jobs in the south east and had a turnover of around £8m a year.
A source confirmed that all the workforce had lost their jobs.