Dear Student,
For getting admission in an IIT for pursuing your B.arch you have to appear for JEE Advanced Architecture Aptitude Test which is an entrance test for admission in B.Arch courses. AAT exam consists of three sections: Mathematics, Aptitude Test & Drawing Test. Below are the only two IIT's that offers B.Arch courses:

• Indian Institute of Technology, Roorkee
• Indian Institute of Technology, Kharagpur

Hope this might help you.