Can I file an intent to Lein on a job in Washington D.C ?

You would have to be a first tier subcontractor, and otherwise licensed to operate within your specific trade in Washington, DC (or at least have a DC business license if no specific trade license was required). Assuming these requirements are met, the DC Lien Law is around specifically to assist people like you! Bear in mind also that in DC, payment is a defense (ie, if the owner already paid the gc for your work, that would preclude any enforcement of a mechanic's lien).

Please feel free to reach out to me privately with any further questions. Good luck!