Is it permissible for an employee to borrow from a company fund that compulsorily deducts a monthly amount from his salary, given that the fund grants loans with non-exorbitant interest, and that these deductions will inevitably be lost to him?

Social security is forbidden (haram). However, there is no blame on the worker for paying what he is obligated to pay, provided he does not take more than he has paid. As for borrowing from the company insured with a contract that stipulates repayment of more than the loan, this is forbidden (haram), and the contract is invalid (fasid). A Muslim must avoid it, whether the borrowing is for building a house or for anything else.