you can pursue Bachelor in Architecture even after completing a diploma in Civil Engineering. The scope for Architecture is increasing day by day in India. The Bachelor in Architecture course is related to the design of bridges, multipurpose buildings, industrial areas, residential area etc. Owing to many ongoing dam and bridge projects in India, there is a huge demand for Architecture students.

Since you have completed a Diploma in Civil Engineering, B.Tech in Architecture is the most logical option for you.

The candidate who has completed a diploma in civil engineering is eligible for the architecture engineering course through the lateral entry scheme offered by the Engineering colleges in India.

Under this scheme, you are eligible for admission for the second year in the Engineering course provided that you have either completed 

• Diploma In Engineering 
• B.Sc course

For you it’s the former case, and thus you can avail the lateral entry scheme and get admission in Architecture.

Now specifically talking about Sir JJ College of Architecture, some key points regarding the eligibility criteria are

• For B.Arch, you should have passed (10+3) Diploma in Engineering/ Technology with Mathematics as a compulsory subject Candidates should have scored a minimum of 50% in NATA (i.e. 80/200)
• If you belong =to SC/ST category, 5% relaxation is offered