Hello Jay,

   Yes you can do B.arch after diploma. You cannot get direct admission, for this you have apply for NATA(National Aptitude Test in Architect) to get admission in colleges which offers Architecture courses. Also remember that not all colleges accept NATA score, so be careful with it. Other option you have is to appear for Jee Mains paper 2. From this you can get admission in NITs, CFTIs(Central Funded Technical Institutes) and in some government colleges. I hope I answered your question.

Thankyou and Good Luck !!