Whether your CPF can be used to repay housing loans after 55, depends on how much CPF savings you have at 55, and how much you have already used for housing.
When you turn 55, a Retirement Account (RA) is created using savings from first your Special Account, then Ordinary Account (OA) to meet the Minimum Sum (MS) relevant to your cohort. While the MS provides monthly payouts from your draw down age, the balance in your OA can be used for housing loan repayments.
Members who are able to set aside more than half of the MS, will be able to use the amount in excess of half of the MS for housing loan repayments.
For example:
If you continue working after 55, your CPF OA contributions can also be used for housing loan repayments.
However, housing withdrawal limits may apply. This is to safeguard members from overspending on their housing loan repayments at the expense of their retirement savings.
Source: InTouch CPF