Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
It will not be permissible to take out a mortgage from conventional banks. As muslims we should adopt permissible methods in purchasing properties and homes etc.
Alternatively, you can take out a loan which is in accordance to Shariah which have been approved and verified by scholars like Mufti Taqi Uthmani, Mufti Abdul Qadir Barkatulla and Sheikh Nizam Muhammed Saleh Yaqoobi.
Please refer to: http://www.muftisays.com/qa.php?viewpage=viewQA&question=942
And Only Allah Ta'ala Knows Best.