DUAL-key homes in private condominiums have been around for years, but much to the surprise of many, HDB flats can also be turned into dual-key concepts.

While this possibility gives owners of Housing & Development Board flats an interesting option to reconfigure their homes for rental, it has also left analysts wary over their potential impact on the public-housing market.

A dual-key home is one that has been divided into two units, but with a common foyer and main door. Typically, the homeowner lives in the larger unit and can rent out the smaller studio space. Such homes first hit the private-housing market in 2009, when Frasers Centrepoint Homes launched its Caspian condominium.