What is the ruling on taking out a loan from a bank to buy a house due to the dampness in the current house and its health effects on the children?

It is not permissible to borrow from a bank with interest, because it is usury (riba). Scholars have unanimously agreed on its prohibition. Allah Almighty says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged."