The proposed new restrictions for lower-priced Build-To-Order flats will apply only to new buyers, leaving the assets of existing flat owners untouched.

National Development Minister Khaw Boon Wan made this clear on his Housing Matters blog on Thursday.

Mr Khaw had floated three ideas on possible restrictions, to keep flats affordable to first-time home buyers.

They are: a longer minimum occupation period before an owner gets to sell his flat, a shorter lease, and separating it from the resale market.

Responding to feedback, particularly from existing owners who might want to sell their existing flats to fund their retirement needs, Mr Khaw said: "Obviously, if we offer such an option, these restrictions ... will only apply to the new buyers, and will not apply to existing flat owners."

He added that the government's goal was to provide affordable housing for new homeowners.

"But we will not forget the interest of the many hundreds of thousands of existing homeowners," he said.

"Some plan to rely on their flat to finance retirement needs. Some hope to bequeath their flats to the next generation. Some rely on renting out a room to bring in extra cash proceeds. Their concerns matter to me too," he said.

He also said he intends to hear the silent majority's views on housing policies, as part of the government's ongoing Singapore Conversation.