Dear Sonal,

Look, First of all Engineering and Architecture are two totally different subjects and the career path of these two domains are also different . So, It's mandatory that in which subject or domain you want to do masters , a basic knowledge in UG about that subject is must required , otherwise you can't access that subject properly .

And 2ndly, for M.Arch , you have to appear for GATE exam and give exam on Architecture paper, so if you haven't read Architecture in UG , then how can you appear for the test?? As per the eligibility of GATE also, you are not eligible to appear for Architecture paper after studying Civil.

For more details about M.Arch , refer this :

https://www.careers360.com/courses/m-arch-master-of-architecture

Hope this helps !