ICS Building Society has written to mortgage brokers announcing changes to lending which become effective tomorrow.
Under the new rules purchasers of one-bedroom apartments will be required to advance a larger deposit.
It has also reduced the amount it is prepared to lend on the basis of an individual's income.
It has reduced the amount of money they are prepared to lend on One-bed apartments in Dublin, Limerick, Galway, Cork cities from 90% of its value to 75%.
It has reduced the amount it will lend on all one-bed apartments elsewhere from 85% of its value to 65%.
It has also announced further changes to the amount they will lend dependent on the value of the house and the income a person or couple who are looking to buy the house have.
The lender has also announced it has reduced the minimum property values they will consider for buy to let mortgages - from €250,000 to €200,000 in Dublin, and further reductions around the country.
It has also extended a maximum interest only period on those mortgages from three years to five years.