All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu 'alayhi wa sallam, is His slave and Messenger. If the person knows that those who ask him to design houses will submit those plans to the bank in order to receive a Riba-based loan, it is impermissible for him to support them. Allaah Almighty says (what means): {but do not cooperate in sin and aggression. And fear Allaah ; indeed, Allaah is severe in penalty} [Quran 5:2]Moreover, he has to forbid them from this evil doing and point out to them the danger of dealing in Riba.Allaah Knows best. (Source: islam_web) Classified in Fiqh of Transactions and Inheritance > Riba (Usury)